Heat-moisture treatment (HMT) and annealing are hydrothermal starch modifications. HMT is performed using high temperature and low moisture content range, whereas annealing uses excess of water, a long period of time, and temperature above the glass transition and below the gelatinization temperature.
Carbohydrate Polymers 274 (2021) 118665 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Review Physical modification of starch by heat-moisture treatment and annealing and their applications: A review Laura Martins Fonseca *, Shanise Lisie Mello El Halal , Alvaro Renato Guerra Dias , Elessandra da Rosa Zavareze Department of Agroindustrial Science and Technology, Federal University of Pelotas, Pelotas, RS 96010-900, Brazil A R T I C L E I N F O A B S T R A C T Keywords: Annealed-starch Combined modifications Food HMT-starch Physical modification Heat-moisture treatment (HMT) and annealing are hydrothermal starch modifications HMT is performed using high temperature and low moisture content range, whereas annealing uses excess of water, a long period of time, and temperature above the glass transition and below the gelatinization temperature This review focuses on: research advances; the effect of HMT and annealing on starch structure and most important properties; combined modifications; and HMT-starch and annealed-starch applications Annealing and HMT can be performed together or combined with other modifications These combinations contribute to new applications in different areas The annealed and HMT-starches can be used for pasta, candy, bakery products, films, nanocrystals, and nano particles HMT has been studied on starch digestibility and promising data have been reported, due to increased content of slowly digestible and resistant starches The starch industry is in constant expansion, and modification processes increase its versatility, adapting it for different purposes in food industries Introduction Starch is a natural, biodegradable, abundant, biocompatible, lowcost, and nontoxic polymer highly used in several industries as textile, food, paper, packages, biomedical, and pharmaceutical In food in dustries, starches are used for the production of instant foods, noodles, baked goods, and food packages, among others Starch presents inherent limitations that can be overcome by its modification through methods as chemical, enzymatic, physical, and a combination of them (Lacerda et al., 2015; Molavi et al., 2018) There are several studies reporting the effect of these modifications in starch properties to suit specific appli cations, such as: Majzoobi et al (2015), who modified rice flour and rice starch by HMT for application in biodegradable films; Chandla et al (2017), who used HMT-amaranth starch for the production of noodles; and Choi and Koh (2017), who used annealed-starch from rice for the same purpose Physical methods have gained widespread acceptance for their low cost, safety, and effective characteristics, being a green (not requiring chemical reagents) alternative to improve starch applicability, by achieving specific enhanced properties for specific types of applications (Punia, 2020) There are various physical modifications such as pregelatinization, a thermal process; heat-moisture treatment (HMT) and annealing, two hydrothermal processes; and the non-thermal modifi cation includes high pressure processing, micronization, ultra sonication, and pulse electric field (Alc´ azar-Alay & Meireles, 2015; Punia, 2020) Annealing and HMT are the most commonly used methods effective in altering starch properties, such as relative crystallinity, water absorption capacity, and pasting properties, maintaining the molecular integrity of starch These hydrothermal treatments also in fluence directly starch digestibility: this is extremely important to ach ieve health benefits for the consumer, by slowly digestible starch (SDS) and resistant starch (RS) formation and reduction of rapidly digestible starch (RDS) Thus, the application in food products can focus in in dividuals with chronic diseases as diabetes, among other serious health issues (Pratiwi et al., 2018; Sudheesh et al., 2020) These changes in starch digestibility are mainly promoted by the disruption in starch Abbreviations: AFM, Atomic Force Microscopy; DIC, D´ etente Instantan´ ee Contrˆ ol´ ee; DSC, Differential Scanning Calorimetry; DV-HMT, Direct vapor-heat-moisture treatment; GRAS, Generally recognized as safe; HMT, Heat moisture treatment; NC-AFM, Non-contact Atomic Force Microscopy; RHMT, Repeated heat moisture treatment; RP-HMT, Reduced-pressurized heat-moisture treatment; RS, Resistant starch; RDS, Rapidly digestible starch; RVA, Rapid Visco Analyzer; SEM, Scanning Electron Microscopy; SDS, Slowly digestible starch; XRD, X-ray diffraction * Corresponding author E-mail address: laura_mfonseca@hotmail.com (L.M Fonseca) https://doi.org/10.1016/j.carbpol.2021.118665 Received June 2021; Received in revised form September 2021; Accepted September 2021 Available online 11 September 2021 0144-8617/© 2021 Elsevier Ltd This article is made available under the Elsevier license (http://www.elsevier.com/open-access/userlicense/1.0/) L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 structure, increasing accessibility of starch molecular chains to the amylolytic enzymes, changing its crystalline structure, and thus enhancing starch digestibility (Wang et al., 2016) The most important structural changes achieved by HMT and annealing are promoted by the extension of double helical lengths, reduction of double helix content, strengthening of interactions between amylose and amylopectin branching, and more heterogeneous semicrystalline lamellae Thus, more mobile chains are available due to the greater proportion of very long chains/branches The starch structure becomes more organized The modification mechanism involves increasing the interactions of starch chains, which starts by disruption of the crystalline structure, followed by dissociation of double helix structures and then reassociation of the disrupted crystals The different starch sources present distinct granule organization and behaviors when undergoing hydrothermal processes: the high amylose starches have potential to form thermostable molecular orders (Li et al., 2020; Pratiwi et al., 2018) Various food applications are cited in the literature for HMT and annealed starches, as in baked goods, noodles, doughs, pie fillings, flours, and whole grains or kernels In processed foods, these modified starches can be used as unmodified thickeners, to improve their stability to temperature, shear, and acid conditions, also reducing retrogradation Other applications are in thermoplastic materials, resins, films, nano particles, and nanocrystals (BeMiller, 2018; BeMiller & Huber, 2015) In addition, the HMT and annealed starches present granules more sus ceptible to chemical and enzymatic modifications and to acid hydrolysis ´zar-Alay & Meireles, 2015) The use of HMT and annealing pro (Alca motes thermal stability for starches, being promising for the develop ment of products that are exposed to high temperatures during production In addition, they are safe and innovative methods that improve the functional and technological properties of starch for in dustrial proposes (Molavi et al., 2018) In this study, we present an updated review (2011− 2021) focused on HMT and annealing, examining their effect on starch structure and the properties of different types of starches, the combination with other modifications, and recent trends in the application of modified starch, based on reports from literature of the last 10 years birefringence These changes influence starch behavior in terms of swelling power and solubility (Singla et al., 2020) Gelatinized starch is used in industries as a thickener, gelling agent, stabilizer, and fat sub stitute in foods (Oliveira et al., 2018) Thermal properties of starch can be measured by differential scan ning calorimetry It provides data of heat flow associated with gelati nization, showing changes in enthalpy related to the transition of ordered and disordered crystals from low order crystalline regions of the granule Through this analysis, the gelatinization temperature is also obtained It defines the proportion of required energy for cooking (Zavareze & Dias, 2011) Another important property of starch is digestibility Starch is clas sified according to its nutritional aspects after ingestion, by RDS, SDS, and RS RDS and SDS are digested and absorbed after passage through the gastrointestinal tract and arrival in the small intestine RS is not digested, being fermented in the large intestine SDS and RS are well known for preventing diseases, showing health benefits Therefore, their application in food industries is growing over the years (Maior et al., 2020; Yan et al., 2019) Starches can be applied in food and non-food industries For this, specific characteristics are required, which are not often achieved by native starches Therefore, starch modifications are alternatives to enhance starch properties They broaden its industrial end-use by providing products with higher thermal and shelf stability, as well as mechanical, texture, and pasting properties, for instance (Falade & Ayetigbo, 2015) Physical modification Physical modifications are low-cost, safer, and green alternatives when compared to chemical and enzymatic processes Their study has been showing promising outcomes on the improvement of starch prop erties (Oliveira et al., 2018) Among the physical modifications are pregelatinization, ultrasonication, heat-moisture treatment, mechanical milling, and annealing They present variations in parameters as tem perature, pH, and pressure, acting by modifying the starch molecular structure, packing arrangements, and crystallinity, for example (BeMiller & Huber, 2015; Singla et al., 2020) Annealing and HMT are hydrothermal processes highlighted by achieving unique starch properties, unaltering its molecular integrity (Obadi & Xu, 2021) In the next sections, we are going to discuss the reported effects of HMT, annealing, and combined methods on starch properties and starch applications Starch composition, structure and properties Starch is a polysaccharide of plant origin formed by two macro molecules with glucose units linked together through glycosidic bonds Amylose is a long and linear macromolecule containing α-(1–4) linkages with helical structure, with hydrogen atoms inside the helix and hy droxyl groups outside the helix Amylopectin is branched, containing α-(1–4) and α-(1–6) linkages arranged radially in the granule, double helix as crystalline areas and branching points as amorphous areas (Rocha et al., 2012; Sudheesh et al., 2020) The amorphous areas are more susceptible to hydrolyses by enzymes and water absorption due to the influence of amylose in the packing of amylopectin crystallites in the crystalline lamellae, which influences swelling and gelatinization (Zavareze & Dias, 2011) Starches can be found with different amylose contents depending on the botanical source: in corn, for example, the normal amylose content for starch is 20–30%; a high amylose content is 50–80%; and a low amylose content is 0–8% (waxy starch) (Obadi & Xu, 2021) The functional properties of starch are related to its botanical source, amylose/amylopectin ratio, molecular weight, and organization of the granule chains (Sudheesh et al., 2020) The X-ray diffraction pattern can exhibit A-type structure with medium length helices showing reduced crystallinity, mostly reported for starches from cereal grains, and B-type with higher length and crystallinity, mostly found for starch from tubers (Moran, 2019) The crystallinity of starch is affected when it is heated in excess of water It undergoes a phenomenon named gelatinization, in which amylose is leached, the granule is swollen and the disappearance of the double-helical crystalline structure occurs along with the loss of 3.1 HMT Hydrothermal processes, such as HMT, are performed by heating the starch granules at temperatures above gelatinization temperature, with moisture content insufficient to gelatinize starch, and submitted to a specific period of time, maintaining granular integrity The parameters used for this starch modification are: high temperature, ranging from 84 to 140 ◦ C; low moisture content, ranging from 10 to 35%; and time of exposure ranging from to 16 h (Adawiyah et al., 2017; BeMiller, 2018) The effectiveness of the treatment depends on the process parameters (moisture content, temperature, and heating time) and the starch characteristics, such as botanical source, structure, and amylose/ amylopectin ratio and organization (Adawiyah et al., 2017; Alc´ azarAlay & Meireles, 2015) HMT influences and improves several starch properties, which are discussed in the following sections Changes in starch caused by HMT include effects on morphology, swelling capacity, crystallinity, gelati nization, thermal stability, retrogradation, digestibility, and pasting properties (Punia, 2020), broadening the range of starch applications in the food industry Table summarizes several studies explored in this review in the following sections, regarding different types of starch modified by HMT and the treatment parameters used L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 starch and 63% for potato starch, both when applied the highest mois ture content in HMT The authors associated this behavior to the evap oration of water molecules during the physical modification The roughness increased for sweet potato starch and decreased for potato starch after the treatment, being the greatest changes for the HMT using 20% moisture content, increasing the roughness by 46% for sweet po tato starch and decreasing it by 40% for potato starch This study pro vides quantitative information about changes in size and roughness of starch granules from different botanical sources, showing that the in fluence of HMT depends on moisture content Lacerda et al (2015) studied avocado starch modified by HMT at 120 ◦ C for h, with moisture contents of 10, 20, and 30% The morphology was analyzed by Atomic Force Microscopy (AFM), and native and modified avocado starches showed an oval shape The native starch presented protruded, flat, and smooth regions, not showing an appropriate order after HMT, but showing a smooth region on the sur face The authors attributed this change to the melting of the protruded regions by partial gelatinization, in which the water molecules evapo rate, causing the amylopectin double helix chains to organize into a denser packing structure In the study of Lacerda et al (2015), the moisture content in HMT was higher than in Oliveira et al (2018) However, the effect of HMT on starch morphology was less pronounced, thus showing that the botanical source of starch plays an important role in the application of HMT Bartz et al (2017)) reported the intense effect of HMT on physico chemical properties, morphology, swelling power, and amylose content, by subjecting potato starch to HMT at 12, 15, 18, 21, and 24% of moisture content for h at 110 ◦ C The effect on these properties has been accentuated along with the increase in moisture content The morphology was evaluated by Scanning Electron Microscopy (SEM), and the native potato starch granules varied in size, showing ellipsoidal shape with some small spherical granules HMT-starches modified with 12, 15, 21, and 24% of moisture content showed similar granule morphology However, the treatment using 18% of moisture presented discrete agglomeration, as well as grooves In their study, the differences in moisture did not promote changes in the effect of HMT In another study, Wattananapakasem et al (2021) examined the morphology of HMT-geminated-black rice by SEM, with moisture con tents of 25 and 30%, treated at 90 ◦ C for and h The authors reported the presence of agglomerations and pores in the granules after applying HMT The increase in time of exposure to HMT from to h did not change the morphology of the rice starch granules In our point of view, this may have happened because, at these treatment conditions, the changes in the granule occurred in full during the shorter time of exposure (1 h) According to the studies presented in this review, the treatment time, moisture, and starch source are determining factors for changes in the morphology of granules promoted by HMT Depending on the starch gelatinization temperature, high moisture contents in the HMT can promote partial gelatinization and agglomeration in the starch granules Table Heat-moisture treatment (HMT) parameters, source of starch, and references Starch HMT parameters Reference Temperature (◦ C) Time (min) Moisture content (%) Sago and arenga Cassava Grain paddy rice and rice starch Potato 120 60, 90 20 120 120 60 10, 30, 60 10, 20, 30 13 110 60 Mango kernels Potato 110 100, 120 180 120 12, 15, 18, 21, 24 20, 25, 30 30, 35 Germinated brown rice grain Green Prata banana Black rice Rice, cassava, and pinh˜ ao starches Avocado Corn 100 60 30 Bharti et al (2019) Brahma and Sit (2020) Chung et al (2012) 102 60 10, 20, 25 Costa et al (2019) 100 100, 120 960 120 30 22 Dhull et al (2021) Klein et al (2013) 120 110 60 960 Lacerda et al (2015) Liu et al (2016) Potato and sweet potato Sweet potato 121 60 10, 20, 30 20, 25, 30, 35 10, 15, 20 110 25 Pranoto et al (2014)) Rice bean Geminatedblack rice Mung bean 110 90 180, 240, 300 960 60, 120 25 25, 30 120, 240, 360, 480, 600, 720 30 Thakur et al (2021) Wattananapakasem et al (2021) Zhao et al (2020) 120 Adawiyah et al (2017) Andrade et al (2014) Arns et al (2015) Bartz et al (2017)) Oliveira et al (2018) 3.1.1 HMT influence on morphological properties Microscopy analysis is used to characterize starch granules, showing its different sizes and shapes (Schafranski et al., 2021) BeMiller and Huber (2015) reviewed various studies regarding starches modified by HMT, and found the following results: direct influence of treatment conditions (e.g., high temperature and low moisture) on starch proper ties when compared with their native counterparts, showing increased mobility of starch chains and helical structures and resulting in major structural changes; molecular degradation of starch chains; and morphological changes to granules as size, surface cracking, hollowing at granule centers, decreased birefringence, and partial gelatinization or agglomeration of granules However, other studies (Andrade et al., 2014; Costa et al., 2019; Lacerda et al., 2015; Pranoto et al., 2014) have not found changes in the morphology of HMT-starches from different sources as organic cassava, green Prata banana, avocado, and sweet potato Oliveira et al (2018) evaluated the morphology of potato and sweet potato starches treated with moisture content of 10, 15, and 20% at 121 ◦ C for h, by Non-contact Atomic Force Microscopy (NC-AFM) The authors reported an agglutination of the granules and changes in size and roughness, when applying HMT to the starches The shape of the granules was not modified by HMT: while native potato starch showed an ellipsoidal shape, the native sweet potato starch presented a polyg onal shape HMT promoted reduction in the size of the granules of po tato and sweet potato starches This was accentuated by the higher moisture content of treatment, with reductions of 17% for sweet potato 3.1.2 Influence of HMT on solubility and swelling power The starch properties of swelling power and solubility elucidate in teractions between the starch chains of crystalline and amorphous structures (Thakur et al., 2021) Repeated heat-moisture treatment (RHMT) has been used by researchers in order to improve the effect of HMT within the starch granules (Niu et al., 2020; Zhao et al., 2020) According to Zhao et al (2020), HMT provides starch with limited de gree of modification Thus, repeated processing allows a redistribution of moisture in the granules during the cooling process, providing a new equilibrium from the new starting point (e.g., previously HMT-modified starches) The authors have modified mung bean starch by HMT at 120 ◦ C for 2, 4, 6, 8, 10, and 12 h, and using RHMT at 120 ◦ C for 2, 3, 4, 5, and h They evaluated solubility at various temperatures ranging from 50 to 90 ◦ C, reporting increase for all treatment times at all tem peratures evaluated, when compared to native starch The swelling L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 power presented the same trend of increased values for the analysis at 50 ◦ C and decreased values as the temperature increased from 60 to 90 ◦ C This may have occurred by the reorganization of amylose and amylopectin molecules, reducing the absorption of water during heat ing The solubility of native starch reported by the authors was not high, ranging from to 8%, with increase in temperature from 50 to 90 ◦ C However, values of about 20% solubility were found for some samples modified and analyzed using 90 ◦ C These variations in solubility and swelling power achieved by RHMT allow more possibilities of starch modification by HMT, opening up a range of applications Klein et al (2013) also evaluated the effect of RHMT on swelling ˜o starches (22% of power and solubility, in rice, cassava, and pinha moisture content, at 100 and 120 ◦ C for h, and then for another h at 100 and 120 ◦ C) Both parameters were decreased by HMT when compared to their native counterparts The swelling power of all starches was reduced with the increase in temperature from 100 to 120 ◦ C When comparing HMT-starch and RHMT-starch at the same treatment temperature, only rice starch showed increased swelling power Thus, the rice starch was more susceptible to a new arrangement ˜o starches The modifications of caused by RHMT than cassava and pinha HMT and RHMT present distinct influence according to the different types of starches, thus providing different outcomes to starches regarding its swelling power and solubility Both properties are very important for starch application, as in bakery and pasta production, in which the starch interacts with water and other ingredients Pranoto et al (2014)) studied sweet potato starches of Indonesian varieties submitted to HMT, for future application in noodle production The modification was performed using moisture content of 25%, at 110 ◦ C for 3, 4, and h The data showed differences for swelling power and solubility among the different potato starch varieties HMT-starches reduced swelling power and increased solubility when compared to their respective native starches This behavior was explained by an expansion in the starch granule, an increase of molecular bond interaction, and the loss of double helix formation of the starch chains when heated in water The treatment time did not affect swelling power or solubility in the sweet potato starches Costa et al (2019) evaluated the effects of HMT on the swelling power of green Prata banana starch, with moisture contents of 15, 20, and 25%, treated at 102 ◦ C for h When increasing the temperature of the analysis (70 to 90 ◦ C), there was an increase in swelling power for native and low-HMT-starches HMT decreased swelling power by the molecular arrangement of starch, which reduced the hydration of the granules This can be related to a reduction in crystallinity, the formation of amylose-lipid complex, and the limit temperature of gelatinization in the starch suspension that breaks the hydrogen bonds and releases the water molecules bound from the hy droxyl groups These changes in swelling power and solubility are important for applications in baked goods and other food products Properties as swelling power and amylose leaching are generally reduced by HMT, thus presenting advantages to the production of starch-based food products This reduction in swelling power is pro moted by the restructuring of starch chains and repositioning of bonds in them In addition, HMT makes the granule more rigid and resistant to heating, conferring a more hydrophobic granule (Mathobo et al., 2021) The starches from different botanical sources of the studies presented in this review showed distinct behavior regarding the effect of HMT on solubility and swelling power Increased values of these properties were found for mung bean starch, while decreased values were found for rice, cassava, pinh˜ ao, potato, and green Prata banana starches viscosity (viscosity at the end of cooling) (Schafranski et al., 2021) The influence of HMT on pasting properties was studied by Costa et al (2019), Wattananapakasem et al (2021), Thakur et al (2021), and Dhull et al (2021), in starches from green Prata banana, geminatedblack rice, rice bean, and black rice, respectively Costa et al (2019) treated green Prata banana starch at 102 ◦ C for h, with moisture contents of 15, 20, and 25%, finding increase in pasting temperature and reduction in breakdown viscosity, tendency to retrogradation, and peak and final viscosities The changes in pasting temperature indicate that HMT provided a swelling initiating at higher temperatures (compared to native starch), which is related to the lower swelling power that the HMT-starch presented (data shown in Section 3.1.2) The reduction in breakdown indicates improvement in shear stability and tendency to retrogradation: this is related to the amylopectin chains that may inhibit amylopectin retrogradation due to the lower formation of double heli ces Wattananapakasem et al (2021) modified the geminated-black rice starch using moisture contents of 25 and 30%, at 90 ◦ C for and h The authors reported improved pasting properties promoted by HMT, as well as higher pasting temperature when compared to native starch They also attributed the improvements in starch pasting properties to the molecular rearrangement in the starch granule The viscosity and pasting temperature were higher for the HMT-starch when compared to native starch The authors did not report changes in pasting properties regarding the time of exposure to HMT, which varied at and h The reorganization of molecular structure is promoted by HMT without breaking the amylose and amylopectin chains, but promotes intense changes in starches, significantly altering the paste profile Thakur et al (2021) modified the rice bean using 25% of moisture content at 110 ◦ C for 16 h, and reported that HMT reduced the peak, breakdown, and final viscosities, and improved the mechanical and thermal stabilities of starch This modified starch did not present setback viscosity, which was associated to reduction in amylose leaching, resulting in a decrease for this parameter Dhull et al (2021) modified black rice starch by HMT, using 30% of moisture content at 100 ◦ C for 16 h, and reported that HMT reduced the peak and final viscosities and increased the breakdown viscosity and pasting temperature These au thors attributed the changes on the pasting properties to a protective shell promoted around the exterior of partially gelatinized starch gran ules after HMT, acting as a barrier to the penetration of water and inhibiting gelatinization and pasting In the studies of Thakur et al (2021) and Dhull et al (2021), the time of HMT applied (16 h) was higher than in other studies: Costa et al (2019) used h and Wattana napakasem et al (2021) used and h of treatment exposure This can also explain the different effect on pasting properties This physical modification can be performed directly in grains: Chung et al (2012) modified germinated brown rice grains, whereas Arns et al (2015) modified paddy rice grains and rice starch Chung et al (2012) found increase in pasting viscosity after HMT This was due to improvement of starch chain interactions, promoting a granular ri gidity that is attributed to the increased volume occupied by the swollen granules in the continuous phase Arns et al (2015) used HMT at 120 ◦ C, with 13% of moisture content and 10, 30, and 60 of treatment, showing reduced pasting temperature, breakdown and setback, and increased peak viscosity, when comparing the grain and starch in their native and modified forms In our point of view, these changes in pasting properties are related to the effect of HMT on the following starch granule characteristics: the strengthening of bonds between adjacent amylopectin chains; increased crystalline lamella; enhanced thermal and mechanical stability; and greater resistance to swelling due to a rearrangement of the internal forces The exterior layers of the grains protected the starch structure; however, HMT had effect even when applied directly in the grains Also, it can be a cost-effective option, since no starch extraction is performed and HMT provides changes and im provements to the granule properties 3.1.3 Influence of HMT on pasting properties The pasting properties of starches are most commonly measured by Rapid Visco Analyzer (RVA), which obtains the following parameters of starch pastes: pasting temperature (temperature that starts the increase in viscosity); peak viscosity (maximum viscosity); breakdown viscosity (difference between peak and minimum viscosity); setback (tendency to retrograde, difference between final and minimum viscosity); and final L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 3.1.4 Influence of HMT on crystallinity The different types of crystallinities (diffraction pattern) of starch granules are characterized by X-ray diffraction (XRD) analysis The diffraction patterns are produced by the packages of hexagonal chains of amylopectin (Schafranski et al., 2021) Basically, the diffraction patterns found in starches are A-, B-, and C-types The A- and B-types differ in their compactness and both show a double helical structure The C-type is considered a mixture of A- and B-types XRD measures the relative crystallinity of starches, which present a semi-crystalline structure with crystalline and amorphous lamellae in its granule Overall, this param eter is reduced by HMT (Khatun et al., 2019) Changes in crystallinity and X-ray pattern promoted by HMT were found in potato and sweet potato starches treated with moisture con tents of 10, 15, and 20% (Oliveira et al., 2018) The native sweet potato starch showed A-type diffraction pattern (with diffraction peaks at (2θ) 15, 17, and 23◦ ) that did not change after HMT However, the diffraction pattern for potato starch changed in intensity from B-type (diffraction peaks at (2θ) 5.6, 17, 22, and 24◦ ) to A-type (diffraction peaks at (2θ) 15 and 23◦ ) These authors also reported changes in the crystalline region of the granules after HMT A decrease in relative crystallinity for both starches was found with gradual increase in the moisture of the HMT applied The most pronounced effect in crystallinity was for the highest moisture contents used in HMT for both starches, decreasing 11% for potato starch and 36% for sweet potato starch, when compared to the native starches HMT promotes dehydration and movement of double helices into the central channel that can induce changes in the diffrac tion pattern and relative crystallinity of starches This movement occurred during the HMT, being likely to disrupt starch crystallites and/ or change the crystalline orientation Other studies also found changes in X-ray pattern when applying HMT in potato starch Brahma and Sit (2020) modified potato starch using HMT at different treatment conditions, applying moisture contents of 30 and 35% for 24 h, then heating at 100 and 120 ◦ C for h They also found changes in X-ray pattern that changed from B-type (native) to A + B type (HMT-starch) The native starch showed peaks at 17.3, 22, and 24◦ (2θ) Changes were found in the intensity of the peak at 17◦ , as well as a merge obtained for the peaks at 22◦ and 24◦ The relative crystal linity was lower for the HMT-starches than for their native counterpart Bartz et al (2017)) treated potato starch using HMT with various moisture contents (12, 15, 18, 21, and 24%) The X-ray pattern pre sented changes varying along with the moisture content of the treat ment The native potato starch showed a B-type pattern (5.6, 15, 17, 20, 22, and 24◦ ), then changing to a mixture of A- and B-types For the starches modified with 12, 15, 18, and 21% of moisture contents, the diffractograms showed changes in the intensity of the pattern (mostly in peaks of 5.6, 17, 22, and 24◦ ) On the other hand, the starch modified using the highest moisture content (24%) presented A-type (15, 20, and 23◦ ) pattern The changes in intensity by using HMT occur due to the disappearance of the double helices among the chains within the starch crystals, resulting in a matrix that is more orderly than in native starch Relative crystallinity decreased with moisture contents of 12 and 15%, and it increased with 21% and 24% contents The changes found in X-ray pattern and crystallinity can be attributed to a partial gelatinization of starch granules, which had influence on other parameters as reported here Depending on the starch source, the diffraction pattern may not change by HMT, as reported by Lacerda et al (2015) in avocado starch The increase in moisture content of HMT from 10 to 20 and then to 30% influenced crystallinity with a reduction of 15% in relative crystallinity for the modified samples (not differing statistically among different moisture content applied) when compared to untreated starch This may be due to the breaking of starch granules that was proportional to the extent in moisture content which promoted partial gelatinization at high moisture content The authors related this behavior to the increase in amorphous area in the semi-crystalline lamella, reducing crystallinity with the excessive heat during HMT Bharti et al (2019) examined mango kernel starches from Indian cultivars modified by HMT, using 25, 30, and 35% of moisture content, at 110 ◦ C for h The different cul tivars presented A-type diffraction pattern with diffraction peaks at (2θ) 15 and 23◦ , which remained the same after HMT For all mango culti vars, relative crystallinity decreased However, the authors did not report the values of crystallinity for all samples, which makes difficult the evaluation of the influence of HMT at different moisture content exposure Andrade et al (2014) modified organic cassava starch using HMT in an autoclave, at 120 ◦ C for 60 min, with 10, 20, and 30% of moisture content The authors reported that the intensity of the treatment (different moisture content) reduced relative crystallinity by 11% for the starch modified using 10 and 20% of moisture content, and by 50% for the starch modified using 30% moisture content, when compared to native starch Thus, relative crystallinity data has been inversely pro portional to the moisture content of the HMT Starches modified by HMT are used for the production of nano crystals This is explored in Section 5, which presents recent trends and applications of starch The changes in crystallinity of HMT starches promote improved properties of the nanocrystals, such as higher ther mal stability than the nanocrystals produced with native starch Thus, the changes in crystallinity broaden the applications of HMT-starch 3.1.5 Influence of HMT on thermal properties Differential Scanning Calorimetry (DSC) evaluates the gelatinization properties of starches when heated in excess of water This endothermic phenomenon can be evaluated by DSC through parameters as gelatini zation, transition temperatures (onset, peak, gelatinization, and final temperatures), and gelatinization enthalpy (Schafranski et al., 2021) Overall, HMT promotes increase in the thermal stability of starches by a shift in the onset, peak, and final gelatinization temperatures to higher values Oliveira et al (2018) analyzed potato and sweet potato starches modified by HMT, reporting an increase in gelatinization temperatures and a decrease in the gelatinization enthalpy This trend was more accentuated for the sweet potato starch than for the potato starch The increase in gelatinization temperatures was attributed to a strengthening of interactions between amylose and amylopectin branching Gelatinization enthalpy is related to the stability of the crystalline domains of starch Thus, we believe that the reduced enthalpy can be explained by the collapse in the crystal structure of starch granules, which were evaluated by XRD (reported in Section 3.1.4) The authors also evaluated HMT with different moisture contents (10, 15, and 20%) and found increase in thermal stability with the in crease in moisture content, when compared to the native starch This is seen by the higher initial temperatures and lower gelatinization enthalpy parameters, which represent the thermal stability of starch granules This outcome could be due to the disruption of the amorphous regions of partially gelatinized amylose and amylopectin, and the structural changes induced The changes in thermal properties promoted by HMT can be attrib uted to the formation of a stable configuration This is due to a realignment of polymer chains with the non-crystalline regions of starch after HMT Reductions in gelatinization enthalpy can be attributed to the disruption of hydrogen bonding in the crystalline region of starch, throughout the exposure to high temperature (Adawiyah et al., 2017) Differences in thermal properties were reported by Lacerda et al (2015), who modified avocado starch by HMT (moisture contents of 10, 20, and 30%) There was an increase in gelatinization temperature and a decrease of approximately 50% for gelatinization enthalpy, only for the sample modified using 20% moisture content A large endothermic event was observed for the starch treated with moisture content of 30%, which made it impossible to measure thermal properties Adawiyah et al (2017) used HMT to modify different starches at 120 ◦ C and 20% moisture content For sago (Metroxylon sago) starch, the HMT exposure time was 60 and for arenga (Arenga pinnata), 90 They reported a shift in gelatinization temperature and reduced gelatinization L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 enthalpy, with 39% reduction for sago starch and 28% for arenga starch The gelatinization temperatures as onset, conclusion and peak, all shifted to higher values when comparing HMT and native starches The increase in gelatinization temperatures indicates an increase in thermal stability rendered by HMT However, the treatment had more influence on some of the starches, as sago This can be explained by the different chain arrangement, the amylose/amylopectin ratio, and other charac teristics that vary for each type of starch Costa et al (2019) modified green Prata banana starch by HMT (at 102 ◦ C for h, with moisture contents of 15, 20, and 25%) The treat ment showed decrease in gelatinization enthalpy by 32% for the HMTstarches when compared to their native counterparts, regardless of moisture content The physical modification also influenced the gelati nization temperatures, decreasing the onset temperature and increasing peak and final temperatures, thus indicating improved thermostability for the starch modified by HMT The effect of HMT on thermal properties can be explained by the perfection of the crystalline areas after in teractions of amylose–amylose and amylose–amylopectin The effect of HMT on gelatinization temperatures is in agreement with the changes in pasting properties found by the authors, shown in Section 3.1.3 content provides different outcomes to starch, which could enable various applications Liu et al (2016) modified corn starch using HMT, with moisture contents of 20, 25, 30, and 35%, at 110 ◦ C for 16 h The modification efficiently increased SDS and RS contents and decreased RDS At the highest moisture content (35%) used in HMT, the RDS presented its lowest value, while SDS and RS had their highest value The degree of hydrolysis decreased with the increase in the moisture content used in HMT We believe that the outcome of their study could suggest the effective application of this physically modified starch in the prevention of chorionic disease Chung et al (2012) used HMT to modify germi nated brown rice grains (moisture content of 30%, at 100 ◦ C for h), in order to evaluate its effect on digestibility The contents of RDS and SDS decreased and RS increased, which is explained by the extended perfection of the crystalline structure of the granule and the retrogra dation of amylose In contrast, Zhao et al (2020) reported reduction in RS and enhanced SDS and RDS of mung bean starch after HMT (30% moisture content, at 120 ◦ C for 2, 4, 6, 8, 10, and 12 h) or RHMT (30% moisture content, at 120 ◦ C for 2, 3, 4, 5, and h) In general, HMT increases RS; thus, the authors explain that the different trend found in their study is due to RS being possibly transformed into SDS by enhanced enzyme susceptibility, and this would be caused by the disruption of starch granules and changes in crystalline structures when the associa tions between starch molecule chains are weakened The SDS and RDS values were higher when comparing the RHMT and HMT modifications, which could be related to the higher relative crystallinity of starches after RHMT Thus, RHMT promoted a starch with greater digestibility, which can be applied in foods with faster energy supply Amylose content in starches can diversify the digestibility and the effect of HMT on this property Wang et al (2016) modified regular corn starch and high-amylose corn starch using HMT, with moisture contents of 20, 25, or 30%, at 120 ◦ C for h The RDS values decreased with the increase in moisture content used in the modification The greater re ductions were found using 30% of moisture content for both starches, with 24% reduction for regular corn starch and 43% for high-amylose corn starch, when compared to their native counterparts The SDS content increased and RS increased drastically when compared with native starches: RS increased by about 1000%, for high-amylose content modified at 30% moisture content Therefore, this study shows that HMT is a great alternative to modify high amylose content starch and produce resistant starch The HMT parameters, such as temperature, moisture content, and the botanical source of starch, promote distinct effect on SDS, RDS, and RS Thus, in order to efficiently apply HMT-starches in applications that require high levels of RS, for example, a thorough study must be performed 3.1.6 Influence of HMT on enzymatic digestibility HMT-starch has potential for the prevention of chronic diseases, due to changes in native starch digestibility Digestion of starch is an enzy matic hydrolysis in which starch is broken down into glucose, which is converted to energy for the human body (Khatun et al., 2019) Studies reporting in vitro methods for measuring starch digestibility are per formed by simulating in vivo conditions (Iuga & Mironeasa, 2020) HMT is widely reported for changes in starch digestibility, enhancing the nutritional value of starch-based products by increasing the SDS and RS contents (Iuga & Mironeasa, 2020) There are specific factors directly related to the effect of HMT in digestibility, such as the starch botanical source, starch properties as crystallinity, granule size, amylose, and amylopectin content, interactions and organization between those two macromolecules, and the process parameters (Pratiwi et al., 2018) According to Khatun et al (2019)), the alteration of starch digestibility by HMT is very important for consumers, since starch digestion is linked with population health, especially for individuals with diabetes These authors reviewed the digestibility of HMT-rice starches and state that the rice starch morphology presents very small, medium, and large granules (comparing to other starch sources), being the last related to the reduced in vitro rice starch digestibility Other starch botanical sources were cited for HMT modification, providing effect in α-amylase susceptibility that was increased for rice, wheat, and potato starches Also, Khatun et al (2019) reported decrease in RDS and increase in SDS and RS in corn, pea, and lentil starches The RS content relies on the processing and storage conditions of food, such as temperature It is also related to several starch properties as gelatinization and retrogradation, crystalline structure, and amylose and amylopectin ratio These factors are crucial for the enzymatic susceptibility of starch (Liu et al., 2016) Normally, reduced digestibility is reported in the literature, confirmed by decreased content of RDS and increased content of SDS and RS This occurs due to structural changes in starch granules, which become more rigid and make it difficult for enzymes to attack during digestion (Chung et al., 2012) Brahma and Sit (2020) performed HMT in potato starched at 100 and 110 ◦ C for h using 30 and 35% of moisture content HMT promoted an increase in SDS and RS, and reduction in the RDS of potato starches When comparing the HMTstarches, the RS values were higher with 35% moisture content, increasing by 95% in the treatment at 100 ◦ C and by 88% in the treat ment at 120 ◦ C This outcome suggests the formation of a rigid structure that reduced the accessibility of the enzymes in the analysis to disrupt starch molecules In the highest moisture content (35%) exposure and the lowest temperature (100 ◦ C), a greater effect on RDS and SDS was obtained The different data reported by the authors regarding distinct parameters elucidate that the influence of temperature and moisture 3.2 Annealing Annealing is a hydrothermal process that subject starch with exces sive (~70%, v/v) or intermediate (~40%, v/v) water content to tem peratures above the glass transition temperature and below the gelatinization temperature of starch, under a period of time that varies from minutes to days The process parameters and starch characteristics define the effect of annealing treatment, as previously discussed for HMT However, in annealing the moisture content does not vary, since the treatment is held in excess of water (BeMiller, 2018; BeMiller & Huber, 2015; Punia, 2020) Table shows the studies here reported on annealing applied to different types of starch, as well as their treatment parameters The following sections explore these studies The effects of annealing on starch properties include: increase in crystallinity, thermal stability, gelatinization temperature, starch gran ular size, and molecular mobility, due to an increase in the mobility of the amorphous regions to a crystalline state It also promotes the reor ´zar-Alay & Meireles, 2015) This ganization of molecular chains (Alca L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 (2021), who assessed Castanopsis fruit starch treated in two steps, first at 40 ◦ C for 24 h and then at 55 ◦ C for more 24 h, totalizing 48 h The authors reported that the granules presented rough surfaces with irregular, polygonal, and spherical shapes, unaltered by annealing, regardless of the number of steps in the treatment Another study re ported no changes in morphology: Song et al (2013) performed annealing in potato and sweet potato starches (at 55 ◦ C for 72 h) Both native and modified starches presented granules without pores and with different morphologies among the cultivars (irregular, polygonal, spherical, oval, round, and bell-shaped) Therefore, we can conclude that the shape of starch granules is not affected by annealing, regardless of the starch botanical source or the annealing treatment parameters Annealing is well known for modifying several properties of starch Morphology is affected when evaluating the size of starch granules; in contrast, its shape and structure are not significantly affected This was confirmed by the studies showed in this review in which starches from different botanical sources were modified by annealing Table Annealing parameters, types of starch, and references Starch Annealing parameters Reference Temperature ( C) Time (min) Germinated brown rice grain Yam 50 1440 50 1440 Sweet potato 50 Corn and wheat Corn Oca 55, 60, 65, 70, 80 50 42, 50 1440, 2880, 4320 30 1440 1440 Corn 63 1440 Waxy starches from corn, potato, rice and barley 10 ◦ C below the temperature of gelatinization Castanopsis fruit Sweet potato and potato Corn 40, 55 55 120, 180, 480, 960, 1440, 2880, 4320 1440, 2880 4320 45 1440, 4320 Oat 50 1440 ◦ Chung et al (2012) Falade and Ayetigbo (2015) Hu et al (2020) Li et al (2020) Liu et al (2016) Puelles-Rom´ an et al (2021) Rocha et al (2012) Samarakoon et al (2020) 3.2.2 Influence of annealing on solubility and swelling power The swelling power and amylose leaching of starch granules are reduced by annealing, which improves the quality of starch paste and gel for application in food products (Mathobo et al., 2021) Shi et al (2021) modified Castanopsis fruit starch using a two-step annealing process (step one at 40 ◦ C for 24 h, then step two at 55 ◦ C for more 24 h) The authors reported substantial decrease in swelling power and solubility after modification; both parameters decreased along with the increase in annealing treatment from step one to two In addition, as temperature increased from 60 to 90 ◦ C, swelling power also increased for native and annealed starches The decrease in swelling power after annealing can be attributed to the increase in crystallinity (see Section 3.2.4) The reduction in solubility indicates that there was a strengthening of the bonds, with an increase in the interactions between amylose and amylopectin molecules, forming a more stable structure and reducing the leaching of amylose Wang et al (2014) performed a comparative study of annealing in waxy, normal, and high-amylose corn starches, using parameters as water excess, at 45 ◦ C for 24 and 72 h The swelling power increased prominently with the increase in amylose content of the starches When comparing native and annealed starches, the modification did not change the swelling power for waxy starch However, swelling power decreased for normal and high-amylose starches, by and 18%, respectively The distinct changes in solubility and swelling power of the starches reported can be attributed to interactions between the starch chains and the amylose-lipid complexes Shi et al (2021) Song et al (2013) Wang et al (2014) Werlang et al (2021) occurs due to the hydration of the granule improving the arrangement of double helices, causing a reversible swelling of the granule and rendering an ordered structure with higher granule stability (Rocha et al., 2012) 3.2.1 Influence of annealing on morphological properties Annealing has been used recently on the modification of different botanical sources of starch, such as yam starch, in which Falade and Ayetigbo (2015) used annealing at 50 ◦ C for 24 h The authors modified the starch of various yam cultivars (water, white, yellow, and bitter) Different outcomes were obtained among the samples, which influenced the functional properties of starch Regarding morphology, the evalua tion was performed in light microscope and for each cultivar, the granules showed different shapes, but annealing did not affect the shapes of any cultivar When compared to the morphology of native yam starches, the differences were the following: the modification changed the size of the water cultivar granules; for the yellow cultivar, annealing promoted reduced mean, modal, and median dimensions of the gran ules; and bitter and white cultivar showed no change in size In this study, the authors reported that not only the botanical source of starch, but also the cultivar influenced the annealed starch properties, due to amylose content, molecular rearrangement and size of amylose and amylopectin chains, among other parameters ´n et al (2021) studied oca starch physically modified Puelles-Roma by annealing at 42 and 50 ◦ C for 24 h The structure of starch granules was not affected by annealing, due to the low temperature used in the process of modification, which is below gelatinization temperature The shape of starch (evaluated by SEM analysis) was not affected either However, the granule size of annealed starch was higher than the size of native starch The same result was observed by Rocha et al (2012), who modified normal and waxy corn starches by annealing in excess of water, for 24 h at 63 and 62 ◦ C, respectively The morphology was evaluated by SEM, showing no changes in granule shape: all granules were round and polyhedral The annealed normal and waxy starches showed more pores and increased pore size in the granule surface, when compared to their respective native starches These changes can be due to a spread of proteins over the starch granule surface, along with annealing application and the weakening in tissue structure under heating, forming a compact shape Again, annealing did not change morphology in the study of Shi et al 3.2.3 Influence of annealing on pasting properties The effect of annealing on starch pasting properties depends on factors as amylose leaching, branch chain length distribution of amylopectin, granule swelling, and relative crystallinity This physical modification promotes more resistance of the granules to deformation by strengthening its intragranular binding forces (Song et al., 2013) Hu et al (2020) evaluated the effect of annealing at different time periods of treatment on sweet potato starch, at 50 ◦ C for 1, 3, and days The authors reported that according to the increase in annealing time, there was an increase in the pasting temperature and a decrease in break down, peak, and final viscosities, as well as in setback (compared with native starch) As annealing time elapsed, these changes in pasting properties became more prominent From the data reported by the au thors, we can see that annealing promoted more resistance to high temperatures and weakened retrogradation, thus improving the pasting properties of sweet potato starch We can attribute the changes in pasting properties of starches treated with annealing to the associations among the chains within the amorphous region of the granule and the changes in crystallinity promoted during this treatment In general, annealing does not change the shape of viscoamylograph curves by RVA Its effect on pasting properties is widely reported, as L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 these are strongly influenced by treatment parameters as exposure time Song et al (2013) modified potato and sweet potato starches using annealing (55 ◦ C for 72 h) The annealed-starches presented reduction in peak viscosity, breakdown, and setback, and increase in pasting tem perature In our point of view, the changes mentioned for pasting properties can be related to improved crystallinity (data can be found in Section 3.2.4) and to the enhancement of the packing arrangement of starch through annealing The decrease in breakdown shows that the starch is more stable during heating and continuous shear This opens up new applications that require starch stability in high temperature Werlang et al (2021) modified oat starch (50 ◦ C for 24 h) using annealing, and it had effect only on setback, which presented a lower value when comparing annealed-starch to its native counterpart In this study, the other pasting properties of oat starch gels remained the same after the modification This outcome showed that in oat starch the effect of annealing did not present the same influence on the pasting properties as for other starches showed here, such as potato and sweet potato starches This elucidates the distinction of treatment response to different types of starch with various structures and characteristics Amylose content is an important factor for obtaining the pasting properties of starches by RVA High-amylose starches did not present a viscoamylograph curve under the conditions used by RVA, due to their low viscosity Therefore, the pasting parameters of high-amylose starches cannot be measured by this analysis Wang et al (2014) annealed corn starches containing different amylose contents (waxy, normal, and high-amylose) at 45 ◦ C for 24 and 72 h In the three starches, annealing had no effect on pasting temperature, decreased peak temperature and final viscosity, and increased final viscosity and setback The time of annealing had effect on these properties, which increased or decreased gradually, as annealing time elapsed The breakdown viscosity decreased after 24 h of annealing and increased after 72 h The studies of Werlang et al (2021), Hu et al (2020), Song et al (2013), and Wang et al (2014) showed the effect of annealing on pasting properties of starches from oat, sweet potato, potato and sweet potato, and corn, respectively The data obtained did not show any trends of increase or decrease in pasting parameters, and the effect of annealing was different for each type of starch cited Nevertheless, when comparing native and annealed starch, changes were observed for all botanical sources evaluated, which can be attributed to the disruption of intra and intermolecular hydrogen bonds of the starch grain in the presence of heat and water 58% and 82% of amylose content, using annealing (at 55, 60, 65, 70, and 80 ◦ C for 30 min) The normal amylose content of starches showed Atype diffraction pattern, while the starch with high amylose content presented B-type pattern These patterns were not changed after annealing, but the relative crystallinity decreased as the annealing temperature increased This study is important for showing that different types of botanical sources, as well as amylose content and modification parameters, can modify starch properties and structure with different outcomes Samarakoon et al (2020) investigated the effect of annealing on the properties of waxy starches from different botanical sources (corn, po tato, rice, and barley) It can be observed in this study that annealing affects the properties and the structure of starches from different botanical sources differently The diffraction patterns were not changed by annealing Native waxy starches from corn, rice, and barley presented A-type pattern and potato starch showed B-type pattern Relative crys tallinity was not changed for barley, rice and potato starch; however, for corn starch it increased by 9% after annealing Another study (Rocha et al., 2012) reported the effect of annealing on normal and waxy corn starches (water excess for 24 h at 63 and 62 ◦ C, respectively) Regarding the amylose content, annealing showed no influence The relative crystallinity of normal amylose content did not change; however, there was an increase of 7% for waxy starch The decreased relative crystal linity found for some studies can be explained by partial gelatinization and helix changes, leading to the destruction and reorientation of starch crystallites For each type of starch and the different amylose content, the effect of annealing was distinct, which occurred for all the studies shown in this review This reinforces that the botanical source of starch is able to change the effect of physical modification When a starch is chosen for application, this needs to be taken into consideration, since the modifications can promote specific outcomes for each starch 3.2.5 Influence of annealing on thermal properties Overall, annealing led to increased onset, peak, and final tempera tures and gelatinization temperature range, and decreased gelatiniza tion enthalpy This improved the thermal properties of starches, broadening their application in food products that are exposed to high temperatures during production Different cultivars of potato and sweet potato starches were modified by Song et al (2013) The gelatinization enthalpy decreased for all cultivars, except for one that also showed increased relative crystallinity (see Section 3.2.4) The onset, peak, and final temperatures decreased, and gelatinization temperature increased upon annealing Modification parameters, such as time of exposure to high temper ature, provide greater influence on the thermal properties of starch According to the increase in days of treatment, annealing provided starches with greater onset, peak, and final temperatures and reduced gelatinization temperature, as reported by Hu et al (2020) The authors performed annealing in sweet potato starch (50 ◦ C for 1, and days) Only in the 5-day treatment did the gelatinization enthalpy of starch increase In 1- and 3-day treatments, this property decreased slightly We believe that this occurs probably due to partial gelatinization during annealing Variations in annealing temperature are also reported to present greater effect Thermal properties improve with the increase in tem perature, as reported by Puelles-Rom´ an et al (2021), who modified oca starch using annealing at 42 and 50 ◦ C for 24 h, using different water ratios (1:2 w/v, being 35 g starch/70 ml distilled water, and 1:6 w/v, being 15 g starch/90 ml distilled water) Annealing led to increase in onset, peak, and final temperatures and gelatinization temperature range, becoming more accentuated as annealing temperature increased The higher temperatures are related to a partial gelatinization of starch during annealing The changes in water ratio did not have effect on the thermal properties, not differing among the samples at the same treat ment temperature Gelatinization enthalpy was not changed by any of the annealing conditions Therefore, we can state that oca starch is more 3.2.4 Influence of annealing on crystallinity The diffraction pattern of starch is mostly not affected by annealing In contrast, HMT-starches show shifts in the diffraction pattern, as shown in Section 3.1.4 The different effect on starch properties among the treatments is directly related to the parameters used in both modi fications, e.g., moisture content, temperature, and exposure time Recently, starches from different botanical sources were evaluated for their diffraction pattern, which did not present any changes (Li et al., 2020; Samarakoon et al., 2020; Shi et al., 2021) Annealing was applied by Shi et al (2021) to modify Castanopsis fruit starch (step one at 40 ◦ C for 24 h and step two at 55 ◦ C for more 24 h) Native starch showed diffraction peaks at (2θ) 5.7, 15.1, 17.2, 22.3, and 23.9◦ This represents a C-type pattern, which was not changed by annealing, regardless of treatment step Relative crystallinity decreased for starch treated with two-step annealing (total of 48 h) when compared to native starch However, the starch modified after only one step (24 h at 40 ◦ C) kept the same relative crystallinity Thus, the addition of a second step in annealing using a higher temperature (55 ◦ C) for additional 24 h increased crystallinity by 19% We believe that this behavior can be attributed to the greater effect of heat, which affects the structure of the starch granule in the second step Amylose content is known to influence the relative crystallinity of starches Li et al (2020) modified three types of wheat starches with 37, 85, and 93% of amylose content, and two types of corn starches with L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 resistant than other types of starch, since the changes in thermal prop erties were achieved using the highest temperatures tested and, even so, there were no changes in gelatinization enthalpy The improvements in thermal properties indicate that annealing enhances the crystal quality of starch by amylopectin aggregation through the rearrangement of amylose, which needs less energy to break the crystal structure due to the weakening of the network Oat starch was annealed by Werlang et al (2021) (50 ◦ C for 24 h) The onset, peak, and final temperatures and gelatinization temperature range increased for the annealed oat starch, when compared to its native counterpart Gelatinization enthalpy reduced by 13% from native to annealed starch, which can be associated to the destruction of the semi-crystalline structure and the melting of imperfect amylopectin crystals The reported studies about the use of annealing on potato, sweet potato, oca, and oat starches showed increased thermal stability All ´n et al., 2021; Song et al., 2013; studies (Hu et al., 2020; Puelles-Roma Werlang et al., 2021) showed reduced onset, peak, and final tempera tures, regardless of the botanical source of starch On the other hand, the gelatinization temperature and enthalpy presented different trends with the application of annealing, when compared to native counterparts new perspectives for science and technologies of starch modification Table summarizes the studies reported for combined modifications using HMT or annealing Combined methods with HMT, such as infrared heating, can be performed in order to achieve the same improved properties in a shorter time and with less energy These combined methods for modification were performed by Ismailoglu and Basman (2015) in corn starch and by Ismailoglu and Basman (2016) in wheat starch In both studies, the authors used microwave with powers of 550 or 730 W, exposure times of 30, 60, or 90 min, and moisture content of 20 and 30% The two studies also had results regarding the botanical source of starch The authors found a retained A-type diffraction pattern; changes in thermal prop erties as increased onset, conclusion and gelatinization temperatures were reported by the realignment of the polymer chain and formation of a stable configuration; the pasting properties were affected by a decrease in viscosity only for the samples treated using 550 W and 730 W and 30% of moisture content We believe that the changes in pasting tem peratures are attributed to changes in crystallinity and the chains in the amorphous region association The authors showed a slight increase in relative crystallinity The effect of heating methods with different impact of vacuum pressure on corn starch properties was investigated by Bahrani et al (2013) using DV-HMT (direct vapor-heat-moisture treatment), RP-HMT (reduced-pressurized heat-moisture treatment) and DIC (D´etente Instantan´ ee Contrˆ ol´ee) An improvement in the swelling capacity of the granules was induced by the intensification of the hydrothermal process DIC promoted larger decrease of about 85% in viscosity when compared to the other modifications, in which a decrease of 58% was found for DVHMT and 53% for RP-HMT In this study, the intensification in hydro thermal process provides significant changes in rheological properties, which can directly affect the functionality and application of starch The 3.2.6 Influence of annealing on enzymatic digestibility The degrading enzymes of enzymatic digestibility initially attack the amorphous regions of starch molecules and then the crystalline regions if they are exposed (Song et al., 2013) After annealing, RDS and SDS contents increased, and RS content decreased when Song et al (2013) modified potato and sweet potato starches The increase in RDS is attributed to the easy and rapid attack of the enzymes of digestion on the amorphous region and melted crystalline defects The loss of the α-he lical structure upon partial gelatinization of annealed starches can explain the increase in SDS and the decrease in RS Shi et al (2021) determined the digestibility of Castanopsis fruit starch after a two-step annealing process (step one at 40 ◦ C for 24 h and step two at 55 ◦ C for additional 24 h) After annealing, RDS content decreased and SDS content increased Interestingly, RS was not changed by annealing, even for the starch that showed increased crystallinity (see Section 3.2.4) Following the same trend, annealing (at 50 ◦ C for 24 h) in corn starch increased SDS and RS contents and decreased RDS, when compared to native starch (Liu et al., 2016) In contrast, Wang et al (2014) annealed corn starches with different amylose contents (waxy, normal, and high-amylose), but found no effect on digestibility Annealing can be promising for the modification of grains such as germinated brown rice, which was modified using HMT (moisture content of 30%, at 100 ◦ C for h) (Chung et al., 2012) When comparing germinated brown rice grains to their modified form, RDS content decreased, RS increased, and SDS remained the same The higher RS content can be attributed to improved interactions in starch chains formed during annealing Therefore, this modification is an effective alternative for controlling the digestibility of grains, which needs to be the subject for future studies Annealing does not gelatinize starch; thus, the increase in RS is due to structural changes as its increased crystallinity and molecular reor ganization Throughout the studies reported to explore the effect of annealing on digestibility (Chung et al., 2012; Liu et al., 2016; Shi et al., 2021; Song et al., 2013; Wang et al., 2014), it could be seen that annealing does not affect the digestibility of the starches Thus, for ap plications that require decreased digestibility, with higher SDS and RS content, annealing must be applied correctly according to each type of starch Table Combined modifications of HMT and/or annealing with other modifications in starches from different sources Starches Modifications Important outcome References Corn DV-HMT/RP-HMT/ and DIC Annealing/dry heating Decreased swelling capacity and viscosity Decreased SDS and RS after treatment for corn starch, increased for potato starch Improved freeze-thaw stability, final viscosity, rheological properties, and solubility Decreased viscosity, thermal and pasting properties Decreased viscosity, thermal and pasting properties Increased thermal properties, SDS and RS Increased SDS, RS, viscoelasticity and thermal stability Decreased swelling power and solubility, increased RS Decreased swelling power and solubility, increased SDS and RS Reduced retrogradation, improved thermal properties and granule stability Bahrani et al (2013) Chi et al (2019) Corn and potato Combined modifications Annealing and HMT can also be performed together or combined with other modifications, such as chemical, physical, and enzymatic Combinations are an asset due to their improvement of properties, opening up new applications in different fields In addition, there are Barley Annealing/ hydroxypropylation Corn HMT/infrared heating Wheat HMT/infrared heating Corn HMT/organic acids Corn HMT/lactic acid Kithul HMT/annealing/crosslinking Corn HMT/extrusion Potato HMT/Amylose‑sodium stearate complexes Devi and Sit (2019) Ismailoglu and Basman (2015) Ismailoglu and Basman (2016) Maior et al (2020) Reyes et al (2021) Sudheesh et al (2020) Yan et al (2019) Yassaroh et al (2021) HMT: Heat-moisture treatment; DV-HMT: direct vapor-heat-moisture treatment; RP-HMT: reduced-pressurized heat-moisture treatment; DIC: D´etente Instantan´ ee Contrˆ ol´ee L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 modified starches showed the same size and shape as native starch with some agglomerations, which is aligned with the reported studies using only HMT: Bartz et al (2017)) and Wattananapakasem et al (2021), who modified potato and rice starches, respectively These studies are shown in Section 3.1.1 Chemical modification along with HMT was also reported to have impact on the digestibility and thermal, structural, and pasting prop erties of corn starch, as evaluated by Maior et al (2020), who combined organic acids (lactic, citric, and acetic) and HMT The authors found no changes in diffraction pattern and a slight reduction in relative crys tallinity for all samples This trend was also found by Ismailoglu and Basman (2015) and Ismailoglu and Basman (2016), who combined HMT and microwave modifications The samples treated with HMT combined with citric acid and lactic acid did not show gelatinization curves; the sample treated with HMT and acetic acid showed a reduction of 15% in gelatinization enthalpy; and the sample treated only with HMT showed no difference for this property The surface of the granules showed in its morphology an increase in pores and some irregularities Regarding digestibility, there was increase in SDS and RS: we can suggest a promising use for the production of low-carbohydrate foods for con sumers with chronic diseases such as diabetes, for example The changes in SDS and RS can be attributed to changes in starch structure as the rupture of the double helices, which is proven by the reduction reported in gelatinization enthalpy Thus, we conclude that these modifications performed together allow the possibility of applying modified starch in functional food, producing higher levels of RS The combined modification of HMT and lactic acid was also evalu ated by other authors (Reyes et al., 2021), presenting changes in corn starch such as reduced relative crystallinity of about 62% for the starch modified only with HMT and about 33% for the starch modified by HMT and lactic acid combined The gelatinization enthalpy presented a similar reduction for the starch modified by HMT and HMT combined with lactic acid, reducing about 62% In addition, increased solubility, viscoelasticity and thermal stability were found Regarding in vitro di gestibility, the modifications combined decreased RDS and increased SDS and RS We can see that combining the modification promoted more accentuated influence on the enzymatic hydrolysis of starch granules by acting more effectively on the enzymatic fractionation of starch chains The combined effects of extrusion and HMT on the physicochemical properties and digestibility of corn starch were studied by Yan et al (2019) The modifications showed decreased swelling power and solu bility, and changed X-ray diffraction pattern from V- to V + A-type The pasting properties improved, with higher enthalpy values of about 133% SDS and RS increased, with a 12% rise for RS: this shows that combined modifications make the granules less susceptible to enzymatic hydrolysis, due to more crystal perfection that leads to a resistance to enzyme digestibility In this study, starch structure, physicochemical properties and digestibility were modified by combining HMT with extrusion, allowing more applications of starch Sudheesh et al (2020) combined different types of modification, performing annealing, HMT, and cross-linking on underutilized kithul (Caryota urens) starch In all combinations performed, no changes were reported for the A-type dif fractogram pattern The authors found a decrease in swelling power and solubility, an increase in gelatinization enthalpy, and increase in hard ness of modified starch gel when compared to native starch The dual modification of cross-linking and HMT promoted the highest relative crystallinity among the other combinations, and these modifications combined also showed higher RS content, with an 18% increase when compared to native starch The RS was higher for all the combined modifications when compared to the modifications performed alone The RS content is generally increased when HMT is combined with other modifications, showing promising applications Thus, changes in starch elucidate improved granular stability and we believe that the confec tionery industry is one of the areas interested in good gel forming capacity The improvement in the modification of starch is related to the possible untangling in the entanglements among starch chains, which induces strong movement of the chains, thus facilitating molecular rearrangement during annealing (Zhong et al., 2020) It should be noted that the effects of annealing or HMT on starch properties are enhanced when these modifications are combined with each other or with other types of modifications The effectiveness of annealing was improved when combined with microwave pretreatment, intensifying starch properties as gelatinization enthalpy, particle size, peak viscosity, and breakdown viscosity Devi and Sit (2019) performed annealing in one and two steps fol lowed by hydroxypropylation on barley starch Relative crystallinity and paste clarity increased, whereas swelling power, solubility, freezethaw stability, and paste viscosities decreased when performing annealing alone When the modifications were combined, they enhanced freeze-thaw stability, final viscosity, paste clarity and tem perature, rheological properties, swelling power, and solubility The use of both physical and chemical modifications improves particular starch properties that can be explored by food industries Dry heating and annealing combined to modify starch are a green alternative for improving starch properties: the synergistic effect of both methods alter starch lamellar thickness, increase double helical orders and improve digestibility (Ashogbon, 2020) These modifications synergistically modulate the starch structure, increasing thermostability and homoge neity and presenting direct influence on digestibility This was reported by Chi et al (2019), who modified corn and potato starches using annealing combined with dry heating, focusing on improvements in starch digestibility SDS and RS decreased after combined modification for corn starch and increased for potato starch This can be attributed to the different molecular structure of those two starches, shown in their diffraction patterns (A-type for corn and B-type for potato) The inter esting data present by Chi et al (2019) showed an increase in efficiency of annealing when combined with dry heating and a significant improvement in digestibility for potato starch It is worth mentioning that the two physical modifications used are green and low-cost For targeting applications as in the prevention of chronic diseases, the in vitro enzymatic digestibility of starch must be further investigated in order to efficiently control the effect of dry heating and annealing per formed together The physicochemical properties of amylose‑sodium stearate com plexes (at concentrations of 2, 5, and 8%) in HMT-potato starch were evaluated by Yassaroh et al (2021) The amylose inclusion complexes were used with sodium stearate as guest molecules The addition of amylose‑sodium stearate complexes reduced starch retrogradation and improved thermal properties, which are promising results for cookingrelated applications Throughout changes in X-ray pattern to V6- type amylose crystallite, the formation of amylose inclusion complexes was proven The combined modifications increased relative crystallinity, pasting temperature and granule stability, and decreased the swelling ability, which was more accentuated than in HMT performed alone The authors explored different applications for the modified potato starch as filler, emulsifier, and thermally stable thickener For future studies, it would be interesting that the digestibility of the starches modified by amylose‑sodium stearate complexes and HMT could be evaluated, since due to the properties obtained it is possible that SDS and RS contents are improved The changes upon starch when using HMT or annealing alone can be insufficient depending on the applications requested Thus, using these physical modifications together or with other modifications promotes more efficient outcomes, as shown in this review by expressive changes in thermal, pasting, and swelling properties, as well as in digestibility Therefore, performing combined modifications can enhance starch functionality, broadening its spectrum of applications Recent trends and applications Starch application has been expanding over the years and 10 L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 researchers have been studying its use for producing several materials as biodegradable films, which are used as food packages (Schafranski et al., 2021) Starch modification is performed to improve specific properties of the films, enhancing mechanical properties and reducing water vapor permeability, an important factor for food package industries The application of starch in food packaging is an increasing trend, exploring the production of biodegradable and/or edible packages, as well as the possibility of active and intelligent packaging The modification of starch meets the need for improved properties, which are required for the applications cited The production of biodegradable films is a promising application for physically modified starches Zavareze et al (2012) developed biode gradable films based on potato starch modified by HMT (110 ◦ C for h), using different starch concentrations (3, 4, and 5%, w/v) The modifi cation provided lower viscosity, solubility and swelling power to the starches, when compared to its native form The mechanical properties of the films were improved by the higher values of tensile strength, young modulus, and elongation at break, when comparing the films based on native and HMT-starches However, the water vapor perme ability increased after HMT It is well known that this is not desired for the application of films as food packaging, since the moisture transfer between food and atmosphere must be avoided Thus, we can state that the biodegradable films based on HMT-starch can be used for packaging, depending on the food characteristics and the desired characteristic for the package Higher water vapor permeability was also found in biodegradable films based on rice flour and rice starch, both modified by HMT, using 20% of moisture content at 120 ◦ C for h (Majzoobi et al., 2015) The authors reported changes in other properties of the films when HMT was performed, such as reduced lightness, transparency, tensile strength, and water solubility Thus, they suggest that the biodegradable films may be suitable for packaging of frigid products, or with less sensitivity to moisture content Indrianti et al (2018)) modified sweet potato starch using HMT (25% of moisture content, at 110 ◦ C for 1, 2, and h) and applied it in the production of edible films The authors found increase in thickness, tensile strength, and elongation at break and decrease in solubility and water vapor permeability of the films produced with modified starch The time of exposure did not have influence on the edible films The great data found by the authors provide quantitative and qualitative information about edible films, being the improved properties of the films an indication that they can be applied in food products in future studies The production of biodegradable films using HMT-starches from different botanical sources as potato, rice and sweet potato (Indrianti et al., 2018; Majzoobi et al., 2015; Zavareze et al., 2012) was reported in this review From these studies we can observe that for sweet potato, the water vapor permeability of the films has decreased, while for potato and rice starches, this parameter has increased The solubility has decreased for all the starches modified by the different studies This distinct data obtained for some properties can be attributed mostly to the variations on starch structure among the botanical sources, but also to the different parameters used in the modifications Different approaches for starch modifications and applications as raw material for production of nanoparticles were revised by Kumari et al (2020)), who showed a wide range of applications for modified starch nanoparticles in food systems, such as encapsulating agents, reinforcement materials, and emulsion stabilizers The authors reported that modifications as HMT improve the thermal properties and relative crystallinity of nanoparticles Interestingly, HMT is being widely applied to modify starch nanoparticles, due to its capacity of increasing the thermal properties and the crystallinity of nanoparticles (Ji et al., 2019; Kumari et al., 2020) Annealing is also used to modify the structure of nanoparticles: Ji et al (2019) modified waxy corn starch nanoparticles by annealing at 55 ◦ C for 6, 12, 24, and 48 h They reported that annealing changed the spherical morphology of the nanoparticles, but maintained their nanoscale size The relative crystallinity of nanoparticles was enhanced according to the increase in treatment time, achieving 19% higher values when compared to native starch nano particles The melting temperature increased, suggesting an effective packing of double helices Physical modifications as HMT, when applied on starch before the production of nanocrystals, are proven to be effective in increasing the yield, decreasing preparation time and increasing relative crystallinity Nanocrystals are the most common application of starch in nanotechnology They are crystalline structures produced mostly by acid hydrolysis of starch and are widely applied in various industries as food, cosmetics, paper, among others (Niu et al., 2020; Zhou et al., 2020) Dai et al (2019) produced HMT-waxy corn starch nanocrystals by acid hydrolysis and reported a higher yield and a shorter period of time to produce the nanocrystals when HMT was used The authors reported that the HMT increased the relative crystallinity of the starch and the starch-nanocrystals and showed pores in the granule structure surface Hence, we can state that the main objective of using HMT in the production of nanocrystals was achieved, since higher yield, short production time, and higher crystallinity were obtained when compared to native starch-based nanocrystals Nanocrystals based on RHMT-waxy corn starch presented higher thermal stability, lower molecular order, and double-helix content when evaluated by Niu et al (2020) Changes in crystalline pattern from Atype to B-type were found, as relative crystallinity increased according to the increase in HMT This property achieved an increase of 15% when compared to native starch Pinto et al (2021) modified pinh˜ ao starch using HMT or annealing, in order to produce starch nanocrystals with improved properties Annealing promoted higher thermal stability and HMT promoted higher yields of nanocrystals and higher relative crys tallinity, when compared to nanocrystals from native starch Dai et al (2019), Niu et al (2020) and Pinto et al (2021) reported similar changes in nanocrystals as the increase in relative crystallinity and yields when comparing starches, native and modified by annealing and HMT We can see that the improvements in properties are directly linked with the nanocrystal applications This indicates that physical modifications can be performed in starch before the production of nanocrystals, so as to improve characteristics and enable applications as raw material in nanotechnology The interest from industries in biodegradable materials (films, nanoparticles, and nanocrystals) is growing They reduce environmental pollution, as less material is disposed in the environment, and they replace synthetic polymers in food packages It can be seen that most of the starch materials mentioned were produced using modified starches Starch is applicable to several sectors of food industries It can be used: as a modifier of texture and viscosity; for gel formation and moisture retention; in baking flour; in pasta; and in instant and fried foods (Alc´ azar-Alay & Meireles, 2015) The demand from consumers for healthier baked goods has been growing over the years Therefore, we can find studies on the partial or total replacement of wheat flour for more nutritional flours, such as barley The modification by HMT can treat starch for undesired properties, enabling its application in gluten-free food products (Iuga & Mironeasa, 2020) Flours can be modified by HMT, being applied in bread matrices and having effect on the techno-functional and nutritional parameters of breads A study performed by Collar and Armero (2018) showed the impact of HMT (15% moisture content, 120 ◦ C and h) on bread, based on a mixture of wheat and whole barley flours The authors aimed at partial substitution of wheat flour by using barley flour as a strategy to create an added value to baked goods When analyzing the breads, a superior functional profile was found in whole barley flour exposed to HMT: it exhibited similar properties to wheat-based bread, such as cell uniformity, smoothness, and taste, being all the properties evaluated dependent on the availability of water in the HMT process of dough making In our point of view, this is an important outcome, since the substitution of wheat flour in breads is known for yielding products with inferior technological properties A similar trend was observed by Collar and Armero (2018) for polyphenol bioaccessibility and anti-radical 11 L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 DPPH activity, regardless of the HMT and the hydration of flours in blended matrices These results show promising applications of the HMT-barley flour in baked goods We can observe that the modifications reported in this review make the starches fit for applications in the production of baked goods for people with chronic diseases (as celiac disease and diabetes) and restrictions on consuming bakery products In the rice industries, microorganisms can be developed during parboiling in the soaking step An alternative for this issue can be the application of HMT in the grain, which presents the advantage of reducing microorganisms at this step of rice processing Another advantage is the inactivation of enzymes that release compounds as sugar, phosphorus and nitrogen in the soaking water Arns et al (2014) have modified paddy rice grains by HMT (13% moisture content, 120 ◦ C and 10, 30, and 60 min), which had effect on rice grain before par boiling Before parboiling the grains, the authors quantified the meta bolic defects, which increased by 23% for the paddy rice grain modified for 60 (the longest treatment time), when compared to the native grain We can explain this behavior by the longer period of exposure to high temperature that increased the chemical reactions, causing the appearance of stains and other changes in the grains Regarding the parameters evaluated after rice grain parboiling, Arns et al (2014) evaluated cooking time and volumetric and gravimetric yields after cooking Cooking time increased by 73% when comparing the native grain to the one treated for 60 This parameter increased gradually with the increase in HMT time However, the parameters of volumetric and gravimetric yield after cooking have shown no difference between the native grain and the ones treated for 10 and 60 min, only increasing for the treatment time of 30 The increased cooking time can be related to a greater internal restructuring in the grain, which would enhance resistance to water absorption, being in accordance with other parameters evaluated, such as pasting properties (i.e., lower values of peak viscosity and final viscosity) According to Obadi and Xu (2021), the quality of noodles is directly linked to starch properties The starch must have high tensile strength, low stick after cooking, and low cooking loss during cooking, and these can be achieved by using modified starches Noodles based on amaranth starch modified by HMT (110 ◦ C for 2.5 h) were produced by Chandla et al (2017)) The authors compare the noodles from HMT-amaranth starch with noodles from native amaranth and corn starches, finding firmer texture, improved taste, and distinct flavor for HMT-starch noo dles Annealing widens the range of applications of starch, since annealed starches can improve food qualities as appearance, shelf sta bility, and emulsification materials (Ji et al., 2019) The use of annealed starches in food products is more often found in the preparation of noodles In poor-quality rice flour, it has been reported that annealing provided soft texture in fresh noodles (BeMiller, 2018) Wang et al (2018) studied the effect of annealing (55 ◦ C for 16 h) on the physico chemical properties of rice starch and the quality of rice noodles Annealing did not change the granule morphology or crystalline pattern of rice starch; however, relative crystallinity increased, and there was decrease in solubility, swelling power, pasting viscosity, breakdown, and setback The application of annealed rice starch in the production of noodles was improved by changes in the gel texture of rice starch Increasing annealed rice starch content in the blends for noodles improved sensory evaluation scores, cooking qualities, and texture properties Therefore, annealing is a promising alternative to be inserted in the industries, in order to obtain rice starch with improved properties for the production of gluten-free baked goods Annealing (50 ◦ C for h) was combined with water-soluble fraction removal to modify flours from different varieties of rice, for the pro duction of noodles Choi and Koh (2017) reported that the treatments in flours reduced cooking losses and improved the textural properties of cooked rice noodles Mouthfeel firmness increased for all varieties It is worth mentioning that this study showed that using this combined modification in noodles improved its functional characteristics without using chemical additives The studies of Chandla et al (2017)), Wang et al (2018) and Choi and Koh (2017) evaluated the effect of HMT on amaranth starch, annealing on rice starch, and annealing combined with water-soluble fraction removal on rice flours, respectively They have in common the application of modified starches in the production of noodles, which was improved regardless of the modification applied Thus, we can state that HMT, annealing and combined modifications produce starches with techno-functional properties that can be applied in noodles Ji (2020) evaluated the effect of annealing (55 ◦ C for 24 h) on the functional properties of corn starch/corn oil/lysine blends and reported that the modified starch had decrease in enthalpy and gelatinization temperature, and maintained A-type crystalline structure Regarding the blend analysis, the gelatinization temperature also increased, suggesting that amylose-lipid interactions restrict water penetration, thus needing higher temperatures for dissociation The blends with annealed starch in its composition showed improvement of its pasting properties and the digestibility assays showed increased content of slowly digestible starch content, showing a good prospect for the efficient modification of the in vitro digestibility of starch The changes in digestibility upon annealing are also obtained in starch food products, which enable the application of annealed starches in food industries Poly(lactic acid)/corn starch blends were produced by extrusion molding (Lv et al., 2015) The blend was annealed, remaining for week at room temperature with moisture content of 60%, and then heated at various temperatures (50, 60, 80, 100, and 120 ◦ C) Increase in thermal stability was reported with the increase in enthalpy, achieving 14% for the most severe treatment (120 ◦ C) compared to the untreated sample There was also improvement in mechanical properties of blends It was concluded that annealing is effective in reorganizing molecular chains, weakening structural relaxation and increasing the crystallinity of ma terials The studies of Ji (2020) and Lv et al (2015) exploit the pro duction of blends using annealed-starches This improved the properties of blends, showing a promising field of applications Currently, the encapsulation of compounds and their incorporation in polymer matrices for application in food packaging are some of the most cited research subjects Regarding this matter, starch is widely used for being a great matrix: it is biocompatible, biodegradable, low-cost, widespread, and non-toxic Ethylene gas was encapsulated into inclu sion complexes based on V-type crystalline starches by Shi et al (2019), which were modified by annealing at temperatures of 30–70 ◦ C and heated in aqueous ethanol solutions of 45–100% (v/v) for 10 In the results for morphology, light microscopy and X-ray diffraction, the au thors could observe an increase in single helices content by annealing When using annealing at 70 ◦ C with 50% (v/v), the ethylene concen tration in the inclusion complexes increased from 8.0–31.8% (w/w) to 18.1–49.6% (w/w), and the inclusion complexes prepared with annealed V-starches showed to be more stable in different storage en vironments This study provides great results regarding technologies for the encapsulation of gas in a renewable and biodegradable matrix, also showing the importance of annealing and its role in the application of starch However, studies using HMT and annealed-starch for encapsu lation of active compounds are scarce in literature, being a great topic to be approached by scientists and technologists Table presents studies regarding the applications of starches modified by HMT and annealing, as well as the effect of these modifi cations on properties of the final products The physical modifications of HMT and annealing showed in Table were performed on starches from different botanical sources and presented distinct and specific influence on starch properties The modifications were chosen by the studies in order to improve determined characteristics for specific applications of the starches in food products and food packages The authors studied applications for noodle and bread production, biodegradable and edible films, nanocrystals, and nanoparticles Each application focused on improving different properties: for noodle production, firmer texture; for HMT-starch noodles, improved taste and distinct flavor; for pro duction of biodegradable films, decreased water vapor permeability and 12 L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 Table Applications of starches, flours or grain modified by heat-moisture treatment (HMT) and annealing Starch/ Flour/ Grain Modification Paddy rice grain HMT Parboiled rice Amaranth HMT Noodles Rice Application Annealing/ Watersoluble fraction removal Noodles Wheat and whole barley flours HMT Bread Waxy corn starch HMT Nanocrystals Waxy corn starch Annealing Nanoparticles Corn starch Annealing Corn starch/ corn oil/lysine blends Sweet potato starch HMT Edible films Corn starch Annealing Rice starch and flour HMT Waxy corn starch Repeated heatmoisture treatments Annealing and HMT Pinh˜ ao starch Poly(lactic acid)/corn starch blends Biodegradable films Nanocrystals Nanocrystals V-type starch Annealing Inclusion complexes for ethylene gas encapsulation Rice starch Annealing Noodles Important outcome Reference Increased cooking time and volumetric and gravimetric yield Firmer texture, improved taste and distinct flavor for HMT-starch noodles Reduced the cooking losses and improved the textural properties of cooked rice noodles; increase in mouthfeel firmness Similarity in bread properties; maintained bioaccessibility and anti-radical DPPH activity Higher yield; shorter period of time in production; and higher relative crystallinity Higher crystallinity; higher melting temperature Improved pasting properties; increased content of slowly digestible starch Higher thickness, tensile strength and elongation; lower solubility Arns et al (2014) Higher thermal and mechanical properties Higher tensile strength, stretch resistance; greater rigidity and extensibility Higher crystallinity; higher thermal stability Increased production yields and thermal stability; decreased crystallinity Higher ethylene gas concentration; higher stability during storage Increased sensory evaluation scores, cooking qualities Lv et al (2015) Table (continued ) Starch/ Flour/ Grain Potato starch Chandla et al (2017)) Modification HMT/ oxidation Application Biodegradable films Important outcome and texture properties Decreased water vapor permeability; increased tensile strength Reference Zavareze et al (2012) increased tensile strength Choi and Koh (2017) Conclusions The modification of starch by HMT and/or annealing affects the structural parameters and physical and functional properties of starch, including crystallinity, morphology, solubility, viscosity, swelling abil ity, pasting, and gelatinization properties, as well as thermal and freeze–thaw stability Improvements in the characteristics of HMTstarch and annealed-starch associated with their possible applications are: (i) reduced solubility and increased gel hardness of starch for use in noodles; (ii) reduction in swelling power for application in biodegrad able films; (iii) increase in SDS and RS for functional food products; (iv) reduction in retrogradation and breakdown viscosity for bakery goods; and (v) increase in thermal stability for frozen food products Annealed-starch and HMT-starch are used in a variety of materials in the food sector, as food packages (e.g., biodegradable films, edible films, nanocrystals, and others), and in food products as pasta, pastry, baked goods, and others These applications are possible because these phys ical methods not generate environmental pollutants Thus, these starches can be added to food products in higher amounts than chemi cally modified starches Promising data regarding starch digestibility was widely reported for HMT, due to enhanced SDS and RS contents, which promote the use of starch in functional food products Future studies on the in vivo di gestibility of modified starch products are needed, as well as an expansion of their applications, so that they reach industrial level more effectively Collar and Armero (2018) Dai et al (2019) Ji et al (2019) Ji (2020) Indrianti et al (2018)) CRediT authorship contribution statement Laura Martins Fonseca: Writing – original draft, Data curation, Investigation, Conceptualization, Writing – review & editing, Visuali zation Shanise Lisie Mello El Halal: Investigation, Visualization, Writing – review & editing Alvaro Renato Guerra Dias: Writing – review & editing, Conceptualization, Funding acquisition Elessandra da Rosa Zavareze: Writing – review & editing, Conceptualization, Funding acquisition, Supervision Majzoobi et al (2015) Niu et al (2020) Declaration of competing interest Pinto et al (2021) The authors report no declarations of interest Acknowledgements o de Aperfeiỗoamento de This study was financed by Coordenaỗa Pessoal de Nớvel Superior - CAPES (Finance Code 001), Conselho ´gico - CNPQ Nacional de Desenvolvimento Científico e Tecnolo ` Pesquisa Estado Rio (306378/2015-9) and Fundaỗ ao de Amparo a Grande Sul (BR) - FAPERGS (17/255100009126) Shi et al (2019) Wang et al (2018) 13 L.M Fonseca et al Carbohydrate Polymers 274 (2021) 118665 References Iuga, M., & Mironeasa, S (2020) A review of the hydrothermal treatments impact on starch based systems properties Critical Reviews in Food Science and Nutrition, 60, 3890–3915 Ji, N., Ge, S., Li, M., Wang, Y., Xiong, L., Qiu, L., Bian, X., Sun, C., & Sun, Q (2019) Effect of annealing on the structural and physicochemical properties of waxy rice 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selected physical and chemical modifications on physicochemical, pasting, and morphological properties of underutilized starch from rice bean (Vigna umbellata) Journal of Food Science and Technology https://doi.org/10.1007/s13197021-04974-0 Wang, H., Zhang, B., Chen, L., & Li, X (2016) Understanding the structure and digestibility of heat-moisture treated starch International Journal of Biological Macromolecules, 88, 1–8 15 ... content, temperature, and heating time) and the starch characteristics, such as botanical source, structure, and amylose/ amylopectin ratio and organization (Adawiyah et al., 2017; Alc´ azarAlay & Meireles,... Corn starch Annealing Rice starch and flour HMT Waxy corn starch Repeated heatmoisture treatments Annealing and HMT Pinh˜ ao starch Poly(lactic acid)/corn starch blends Biodegradable films Nanocrystals... morphology of HMT-starches from different sources as organic cassava, green Prata banana, avocado, and sweet potato Oliveira et al (2018) evaluated the morphology of potato and sweet potato starches