High methoxyl pectin from the soluble dietary fiber of passion fruit peel forms weak gel without the requirement of sugar addition

Passion fruit peel (PFP) is a by-product from the fruit processing industry, accounting for approximately 50 % of the fruit weight. It is well known for its health properties, although few studies evaluated its rheological properties. PFP polysaccharides (PFPP) contain a high methoxyl pectin (HMP), specifically a 70 % methylesterified homogalacturonan.

Carbohydrate Polymers 246 (2020) 116616 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol High methoxyl pectin from the soluble dietary fiber of passion fruit peel forms weak gel without the requirement of sugar addition T Kahlile Youssef Abbouda, Marcello Iacominia, Fernanda Fogagnoli Simasb,*, Lucimara M.C Cordeiroa,* a b Department of Biochemistry and Molecular Biology, Federal University of Paraná, CP 19.046, CEP 81.531-980 Curitiba, PR, Brazil Department of Cell Biology, Federal University of Paraná, CEP 81.531-980 Curitiba, PR, Brazil A R T I C LE I N FO A B S T R A C T Keywords: Passion fruit peel Soluble dietary fibre High methoxyl pectin Rheological analysis Passion fruit peel (PFP) is a by-product from the fruit processing industry, accounting for approximately 50 % of the fruit weight It is well known for its health properties, although few studies evaluated its rheological properties PFP polysaccharides (PFPP) contain a high methoxyl pectin (HMP), specifically a 70 % methylesterified homogalacturonan Flow behaviour analysis of PFPP (with or without sucrose) revealed a shearthinning non-Newtonian behaviour Dynamic oscillatory tests showed a weak gel-like behaviour, even without sucrose addition Moreover, under simulated pasteurization process PFPP maintained its gel structure Taken together we demonstrated that PFPP has divergent behaviour from commercial HMP, since it does not require sucrose or low pH to form gel The present work reinforces the use of PFP as a source of soluble dietary fibres and pectins, providing its alternative application as a rheological modifier in a wide range of products, including those with low sugar Introduction Passion fruit peel (PFP) is a by-product from the fruit processing industry and it accounts for approximately 50 % of the fruit weight Brazil is the largest passion fruit producer worldwide, responsible for more than 80 % of the production, reaching approximately five hundred thousand tons of fruit in 2017 (Albuquerque et al., 2019; de Souza, Jonathan, Saad, Schols, & Venema, 2018; Souza & Gerum, 2017) The underutilization of these peels may represent an important environmental issue However, it could also represent a good source of bioactive components such as antioxidants, dietary fibres and vitamins The recovery of by-products holds great potential to be used as food additives by the food industry, as well as functional food ingredients or nutraceuticals to be used for the prevention or treatment of human conditions (Albuquerque et al., 2019; Kowalska, Czajkowska, Cichowska, & Lenart, 2017) Therefore, these (by) products represent a potentially convenient resource to be explored and their transformation on high-added value compounds may be conducted towards the reduction of their impact in the environment For most consumers, the acceptability of industrialized products for daily use is improved when natural ingredients are added instead of synthetic ones (Kowalska et al., 2017) ⁎ Accordingly, PFP has been widely studied regarding its healthpromoting properties, including its metabolic effects (reduction of the fasting blood glucose, triglycerides and glycated hemoglobin levels, reduction of homeostasis model assessment for insulin resistance index -HOMA IR and of the hepatic cholesterol levels), and action on the gastrointestinal tract (gastroprotection, reduction of faecal pH and increase in the faecal moisture) (Abboud et al., 2019; Corrêa et al., 2014; de Queiroz et al., 2012; de Souza et al., 2018; Macagnan et al., 2015; Ramos et al., 2007) Furthermore, it contains dietary fibre (DF), mainly pectin, which is considered a soluble dietary fibre (SDF) SDF are undigestible food compounds which comprises polysaccharides, such as pectins, β-glucans, gums and some hemicelluloses (Englyst, Liu, & Englyst, 2007) Pectin is considered a traditional food ingredient and additive due to its emulsifying, gelling, thickening as well as stabilising properties, thus it has been widely studied for its physical-chemical and rheological properties (Lopes da Silva & Rao, 2007) Despite its availability in a large number of plant species, commercial sources of pectin are limited to citrus and apple pomace, both by-products of the juice industry (Chan, Choo, Young, & Loh, 2017; Kowalska et al., 2017) The search for feasible alternative sources of pectin is increasing, as also the pectin market, which is expected to grow and may reach 1370 million US$ by Corresponding authors E-mail addresses: ferfs@ufpr.br (F.F Simas), lucimaramcc@ufpr.br (L.M.C Cordeiro) https://doi.org/10.1016/j.carbpol.2020.116616 Received 21 March 2020; Received in revised form June 2020; Accepted June 2020 Available online 12 June 2020 0144-8617/ © 2020 Elsevier Ltd All rights reserved Carbohydrate Polymers 246 (2020) 116616 K.Y Abboud, et al study the end of 2025 (www.marketwatch.com) An important factor to choose novel sources of pectin is the yielding In this sense finding new sources of pectin from different by-products, with distinct chemical properties, would broaden their application as food additives, nutraceuticals or even biofuels This may contributes to solve the problem of waste management, which has been estimated in millions of tons every year, and its consequent adverse impact in the environment (Kowalska et al., 2017) Homogalacturonan (HG) is the main component of pectins It comprises the “smooth region” of pectic domains, and is a linear homopolymer of α-1,4-linked-D-galacturonic acid (GalpA) units that can be methyl esterified at O-6 in different degrees This is indicated by the degree of methyl esterification (DE), which is expressed as the percentage of the total number of galacturonic acid residues esterified with a methoxyl group Depending on DE, pectins can be classified as the High-Methoxyl (HMP, where DE > 50 %) and Low-Methoxyl (LMP, where DE < 50 %) (Chan et al., 2017; Einhorn-Stoll, 2018; Yapo, 2011) HMP are well known regarding their gelling properties, for so they are widely exploited by different types of industries as a rheology modifier and stabilizer, as well as in sugary products (Lopes da Silva & Rao, 2007) HMP behave differently from LMP In order to form gel, HMP requires low pH (< 3.5) conditions and high sugar concentrations (> 55 %), while LMP require divalent ions, such as calcium, and wider range of pH (2–6), but have no need for sugar addition (BeMiller, 2019; Chan et al., 2017) The acidic pH promotes the decrease of electrostatic repulsive forces among high methoxyl pectic chains by the protonation of the carboxyl groups To decrease the water activity and boost chainchain interactions, large amount of sugar (i.e sucrose) are used with HMP Lastly, HMP gel formation is governed by two main non-covalent types of interactions: hydrophobic interactions between methoxyl groups; and, hydrogen bonds set between secondary alcohol groups and non-dissociated carboxyl (Oakenfull & Scott, 1984) For those reasons, as well as to their ability to form spreadable gels, HMP is mainly applied to jellies, jams, preserves and marmalades (BeMiller, 2019) There is limited information regarding the rheological properties of passion fruit pectins Yapo and Koffi (2006) evaluated the gelling ability and viscoelastic properties of a low methoxyl pectin extracted from passion fruit peel from Ivory Coast, while Canteri et al (2010) determined the reduced viscosity of an HMP obtained from different portions of PFP (exocarp, mesocarp and endocarp) extracted with 0.05 mol/L nitric acid at 80 °C We have chemically characterized a high methoxyl pectin (DE 70 %), extracted from passion fruit peel (Abboud et al., 2019), with Mw 53 kDa and composed mainly of galacturonic acid (92 %) It presented higher DE and lower neutral monosaccharides amounts compared to other sources of HMP (Barbieri et al., 2019; Colodel, Vriesmann, & Petkowicz, 2019; Nascimento, Simas-Tosin, Iacomini, Gorin, & Cordeiro, 2016) Since these structural characteristics are important for the rheological properties of high methoxyl pectins (May, 1990; Thakur, Singh, & Handa, 1997), the main objective of this work was to evaluate the rheological properties of the high methoxyl pectin extracted from PFP aiming its application as a rheological modifier by the industry in a wide range of products, including those with low sugar 2.2 Sample preparation and rheological analysis PFPP dispersions were prepared in ultrapure water at 2% and 4% (w/w) concentration being stirred overnight at room temperature Samples with sucrose were prepared according to Vriesmann, Silveira and Petkowicz (2010) PFPP at 2% (w/w) and sucrose at 25 % or 50 % (w/w) were mixed and stirred overnight Then, the mixture was heated at 92 °C for 15 in a water bath, under stirring, after that it was cooled and its pH adjusted to 3.0 with a saturated solution of citric acid Lastly, these samples were hermetically sealed and stored at °C for or days until analysis A HAAKE MARS II rheometer was used to conduct analysis, at 20 °C with a cone-plate (C60/2◦TiL) measurement system with maximum gap of mm The temperature was controlled by a circulating water bath (DC5, Haake) coupled to a Peltier temperature control device (TC81, Haake) In order to allow the equilibrium of the temperature in the sample dispersions, they were placed on the rheometer plate for 300 s before all rheological analysis Flow curves were assessed in the controlled shear rate (CR) mode through the application of increased shear rate (0.001 - 1000 s−1) for 300 s The shear stress (τ) and the apparent viscosity (η) were evaluated as a function of shear rate and, the data of flow curves analysed and fitted according to the rheological models of Herschel–Bulkley (τ = τ0 + Kγ˙ n) and Ostwald–de Waele (τ = Kγ˙ n) , where τ is the shear stress (Pa), K is the consistency index (Pa sn), γ˙ is the shear rate (s−1), n is the flow behaviour index (dimensionless) and τ0 is the yield stress (Pa) (Rao, 2007) The frequency sweeps were carried out with controlled deformation mode using 1% strain in the 0.02–10 Hz range G’, which is the elastic modulus associated to the solid response of the material and, G” which is the viscous modulus, corresponding to the fluid response of the material (Zhong & Daubert, 2013), were analysed In order to study the behaviour of PFPP dispersions after they were submitted to pasteurization processes, which is a relevant procedure to food products, the rheometer plate was previously heated to 88 °C and PFPP dispersions were poured on the warm plate, resting for one minute The sensor was covered with a sample hood (POM 222–1903) to prevent water evaporation Subsequently, the temperature decreased to °C at a rate of °C per minute, at a fixed frequency of Hz and strain of 1% The rheological and statistical parameter were obtained by the software RheoWin Data Manager All the analyses were performed, at least, in three independent experiments Graphics show the mean values and corresponding standard error of the mean (SEM) 2.3 Scanning electron microscopy (SEM) PFPP was analyzed by scanning electron microscopy (SEM) (Model VEGA3 LMU, Tescan, Kohoutovice, Czech Republic), equipped with a detector (SDD 80mm2) and AZ Tech Advanced software The electron micrographs were obtained at a 15-kV accelerating voltage The lyophilized PFPP was posed on aluminum stubs with double-face tape Then, it was submitted to metallic coating with gold for with thickness of 10 nm, under argon atmosphere, using metallic coating equipment (Model SCD 030, Pfeiffer, Balzers, Liechtenstein) This procedure was carried out at the Electron Microscopy Center at the Federal University of Paraná, Curitiba, Brazil Material and methods 2.1 Extraction of the passion fruit peel pectin (PFPP) The high methoxyl pectin (PFPP) analysed here was previously extracted and chemically characterized as homogalacturonan by Abboud et al (2019) Briefly, passion fruit peel flour was submitted to the standard enzymatic-gravimetric method (Lamothe, Srichuwong, Reuhs, & Hamaker, 2015) and fraction containing soluble dietary fibres, which corresponded to 20 % of passion fruit peel fibres, was composed of an HMP and corresponds to PFPP fraction employed in the present Results and discussion 3.1 Steady-state shear properties of PFPP dispersions with or without sucrose Flow behaviour analyses of PFPP dispersions at different Carbohydrate Polymers 246 (2020) 116616 K.Y Abboud, et al Table Rheological parameter based on PFPP flow curves Rheological Model Ostwald de Waele Herschel-Bulkley PFPP K (Pa.s) n r2 τ0 K (Pa.s) n r2 2% PFPP 2% 4% 25 % Sucrose 50 % Sucrose 0.2132 0.6062 0.9939 0.3971 0.1220 0.6879 0.9984 2.148 0.4792 0.9936 1.859 1.308 0.5524 0.9971 1.971 0.4946 0.9921 2.243 1.072 0.5839 0.9974 4.303 0.5208 0.9943 4.406 2.669 0.5912 0.9976 betaceum Thus, it can be hypothesize that in the PFPP the junctions zones arising from hydrophobic non-covalent interactions can be formed in large amounts without sucrose and when this co-solute is added only minor of these interactions were newly established Furthermore, in that system the hydrogen bonds seems to be less decisive in gel network, since sucrose could also facilitate this type of interaction (May, 2000; Thakur et al., 1997; Strӧm et al., 2014) Flow curves experimental data were fitted to rheological models, such as Ostwald de Waele and Herschel-Bulkley with high regression coefficients (R2) values (≥ 0.99) (Table 1) These models are important since they may contribute to characterize flow behaviour of fluids on shear Chemical and physical properties of fluids may influence flow behaviour affecting industrial systems productivity and improvement, as well as the orientation of equipment operation regarding heat transfer phenomenon, velocity and volumetric flow rates in channel and tube flows (Doran, 2013; Rao, 2007) The Ostwald-de Waele model, also referred as power law model, stipulate parameters of flow behaviour (n) and consistency (K) index, in which shear-thinning fluids present n < (Rao, 2007) As shown in Table 1, all samples demonstrated flow behaviour (n values) lower than 1, indicating shear-thinning behavior Similarly, Herschel-Bulkley models also provide information on flow behaviour and consistency index, although with an extra parameter, the yield stress (τ0), in which non-Newtonian fluids demand finite stress (τ0), a necessary stress to fluid to start to flow Accordingly, these materials behave as rigid solids until the yield stress is exceeded and the material flows as shear-thinning fluid, therefore samples presenting positive τ0 values, will flow as power-law fluid (Alexandrou, McGilvreay, & Burgos, 2001) As represented in Table 1, τ0 values were increased as the sample concentration increased, and the same occurred for the samples prepared with sucrose Fig Influence of shear rate (0.001 - 1000 s−1) on the apparent viscosity of PFPP from passion fruit peel at 25 °C at different concentrations on water, with or without sucrose concentrations, with or without sucrose addition, were performed to evaluate apparent viscosity in response to increasing shear rates (Fig 1) The results for both, PFPP aqueous dispersions at and 4% (w/ w) showed that the increasing concentrations of PFPP improved the apparent viscosity of the solution Also, PFPP presented a characteristic shear-thinning non-Newtonian behaviour, in which the viscosity decreases with increased shear rates This is considered a typical behaviour for polysaccharide systems, where the three-dimension network of the molecules exhibit a tendency to align on the flow direction, dissociate or assume another conformation thus, reducing viscosity (Lapasin & Pricl, 1995; Schramm, 2006) Likewise, this outline was seen in water solutions, at different concentrations, of HMP extracted from alternative sources (other than citrus and apple pomace pectin) (Chan et al., 2017; Schramm, 2006) PFPP at 2% and 4% (w/w) exhibited apparent viscosity values of 20.9 and 118 Pa.s at 0.01 s−1, respectively These values were much higher than those found for other HMP extracted from non-commercial sources Nascimento et al (2016) found an apparent viscosity of approximately 0.2, 1.5 and Pa.s at 0.01 s−1 for an HMP from the pulp of Solanum betaceum at 3%, 5% and 8% (w/w) respectively Likewise, HMPs from Campomanesia xanthocarpa Berg fruit (Barbieri et al., 2019), ponkan peel pectin (Citrus reticulata Blanco cv Ponkan) and from commercial citrus pectin (Colodel et al., 2019), at concentration of 5% (w/w) presented apparent viscosity values close to 10 Pa.s under shear rate of 0.01 s−1 Pectin from cocoa pod husks had apparent viscosity values even low, approximately Pa.s at the same shear rate (Vriesmann & Petkowicz, 2013) In this sense, it is important to highlight that PFPP aqueous dispersions were 2–15 times more viscous than other HMPs The viscosity of aqueous HMP generally are improved by addition of high amounts of co-solutes, such as sucrose Thus, we evaluated flow behaviour of PFPP at 2% added with sucrose (25 % and 50 % w/w) (Fig 1) As expected, the apparent viscosity of PFPP at 2% was improved by the addition of sucrose, although it was not observed the same enhancement when the sucrose amount was doubled It is known that sucrose decrease the water activity in aqueous dispersions of HMP and further favour the junction zones establishment, increasing hydrophobic association between methoxyl groups from galacturonic acids units (Thakur et al., 1997) However, in general, the viscosity improvement with high amounts of sucrose (as 50 % w/w) can reach to 100,000 fold more than that observed without sucrose HMP from Solanum betaceum (at 3%; w/w) showed an enhancement in the apparent viscosity at 0.01 s−1, from 0.2 Pa.s to near 20,000 Pa.s after addition of 50 % (w/w) sucrose (Nascimento et al., 2016) PFPP at 2% with 50 % sucrose showed only a 9-fold increase in the apparent viscosity, from 21 Pa.s, at 0.01 s−1, to near 188 Pa.s (Fig 1) PFPP had lower Mw, low amounts of neutral side chains and higher DE than HMP from S 3.2 Dynamic rheological properties of PFPP with or without sucrose One of the most important properties of pectins, as a raw material for the industry, is their capacity to form gel HMP dispersed in water usually demonstrated a liquid-like behaviour, where G” is higher than G’ in the whole frequency range analysed (Barbieri et al., 2019; Nascimento et al., 2016; Vriesmann & Petkowicz, 2013; Vriesmann, Silveira, & Petkowicz, 2010) Interestingly, as seen in Fig 2A, PFPP aqueous dispersion at and 4% concentration (w/w), demonstrated weak gel-like behaviour, where the elastic modulus (G’) presented higher values than the viscous modulus (G”) in the whole frequency range analysed, although these moduli are somewhat frequency dependent As observed for other polysaccharides, the gel strength was concentration dependent, and PFPP gel at 2% presented lower strength than PFPP at 4% (Table 2) The dramatically increases on G’ and G” values in frequency sweep (up to Hz) of PFPP at 2% (Fig 2A) could suggest that low concentrated weak gel system was less resistant and maybe at higher frequencies there is untangled in the gel network structure A weak gel behaviour was also observed for 2% PFPP added with 25 Carbohydrate Polymers 246 (2020) 116616 K.Y Abboud, et al Fig Frequency sweeps at 25 °C of PFPP aqueous dispersions with or without sucrose Elastic modulus (G’) is represented with full symbols while viscous modulus (G”) with open symbols (A) Frequency sweeps from PFPP at 2% and 4% (w/w) (B) Frequency sweeps from PFPP at 2% with 25 or 50 % sucrose (w/ w) (C) Comparison between the elastic modulus of all samples Fig Viscoelastic evaluation of PFPP weak gels under cooling after pasteurization simulated method, with or without sucrose Elastic modulus (G’) and viscous modulus (G”) as a function of temperature (A) PFPP at 2% and 4% (w/ w) (B) PFPP at 2% with 25 or 50 % sucrose (w/w) (C) Comparison of elastic modulus (G’) of all samples % or 50 % of sucrose (Fig 2B, Table 2) Sucrose is a co-solute used to promote gelation of HMPs, which generally are viscoelastic liquids in the absence of a co-solute (May, 2000; Thakur et al., 1997) This expected behaviour was not observed here (Fig 2B), since although sucrose increased the gel strength, it was not essential to gel network establishment As described in the above section, it seems that sucrose is not essential to establish in PFPP the junction zones arising from hydrophobic non-covalent interactions necessary to gel network formation Thus, PFPP showed a distinct feature, it forms weak gels in water (G’ > G” in all the analysed frequency range) without requirement of co-solutes or acidification Barbieri et al (2019) also observed a gel-like behaviour for a pectin at 5% (w/v) aqueous dispersion from Campomanesia xanthocarpa Berg., however, the gel was weaker (G’ values around Pa, from 0.03 to Hz) than PFPP at 4% (w/w), which showed G’ values around 55 Pa in this frequency range Table Elastic modulus obtained in dynamic oscillatory tests and ratio G’/G” of all samples, at different concentrations and frequencies Samples PFPP 2% PFPP 4% PFPP 2% 25 % Suc PFPP 2% 50 % Suc Frequency (Hz) G’ (Pa) G’/G” G’ (Pa) G’/G” G’ (Pa) G’/G” G’ (Pa) G’/G” 0.02 0.1 10 3.70 ± 0.21 7.4 ± 0.88 42.48 ± 1.66 6.65 ± 0.63 17.05 ± 0.75 4.06 ± 0.58 36.88 ± 14.44 3.37 ± 2.28 4.75 ± 0.36 11.05 ± 1.77 53.54 ± 2.04 8.26 ± 0.91 25.55 ± 0.69 5.42 ± 0.52 63.84 ± 11.95 4.02 ± 1.18 5.44 ± 0.42 5.08 ± 0.8 64.94 ± 2.05 5.48 ± 0.67 34.72 ± 2.47 3.97 ± 0.54 96.87 ± 13.87 3.13 ± 0.77 nd nd 80.10 ± 2.33 2.72 ± 0.3 49.35 ± 3.14 2.00 ± 0.22 148.48 ± 20.38 1.73 ± 0.41 Carbohydrate Polymers 246 (2020) 116616 K.Y Abboud, et al Fig Scanning Electron Microscopy of PFPP (A) 100×, (B) 1000× and (C) 5000× magnifications (Barbieri et al., 2019; Colodel et al., 2019; Nascimento et al., 2016; Sousa, Nielsen, Armagan, Larsen, & Sørensen, 2015; Yoo, Fishman, Hotchkiss, & Lee, 2006) Min et al (2011) observed that the extraction methods may influence the rheological behaviour of pectins obtained from apple pomace PFPP was isolated by the enzymatic-gravimetric method, known to preserve the original chemical features of the isolated molecules The use of strong acids or high temperatures may be associated with alterations in the HMP structure (Adetunji, Adekunle, Orsat, & Raghavan, 2017; Lopes da Silva & Rao, 2007) Besides, the use of strong acids is associated with environmental damage by producing hazardous contaminants Therefore, enzymatic methods are usually considered environmentally friendly and a potential alternative method (Adetunji et al., 2017; Min et al., 2011) 3.3 Viscoelastic behavior of PFPP samples under pasteurization-like process As HMP may be used as a rheological modifier (additive) in food and other products, it would be wise to evaluate its behaviour under thermic treatments, such as pasteurization, which in turn is a widely used procedure by the food and pharmaceutical industries, aiming microbiological safety of products (Lewis & Heppell, 2000) HMPs usually formed thermo-irreversible gels, since heating and cooling processes may strongly affect the intra- and intermolecular interactions that are important to maintain the HMP gel network (Lopes da Silva & Rao, 2007) Heating can be used in food products during the processing as a way to prevent microorganism contamination in a pasteurization procedure Thus, we submitted PFPP samples, with or without sucrose, to a pasteurization-like condition Samples were subjected to 88 °C, during one minute and after that they were cooling down to °C (at a rate of °C/ min), and G’ and G” were analysed during the cooling process In this experimental approach it was possible to see that during cooling from 88 °C to °C the G’ modulus was higher than G” for all PFPP samples (Fig 3), indicating that the weak-gel behavior was maintained over this temperature range PFPP at 2% showed slight decrease in both moduli from aprox 60 °C to 40 °C being stabilized from 40 °C to °C We cannot discard the hypothesis that at this concentration and under higher temperatures there is a better condition for the interactions between PFPP polymers chains, although the graph showin data from PFPP at 2% is very noisy due low precision of cone-plate system to determine those low G’ and G” values An expected behavior, as reported by other studies (May, 2000; Nascimento et al., 2016; Schramm, 2006; Silva & Gonỗalves, 1994; Simas-Tosin et al., 2010; Ström, Schuster, & Goh, 2014) were observed for PFPP at 4% and to PFPP at 2% with sucrose, where G’ and G” slightly increased under cooling This behavior probably occurred due to formation of new intra- and inter-molecular interactions stabilized by nonpermanent cross-links of gel networks after cooling (Shaw & MacKnight, 2005; Thakur et al., 1997) The differentiated rheological behaviour of PFPP may be related to some structural and physical characteristics and/or method of extraction It can be observed that its monosaccharide composition presented 92 % of GalpA This is a high value when compared with those HMP from other fruits, which showed values from 33.5%–84.5% (Barbieri et al., 2019; Colodel et al., 2019; Min et al., 2011; Nascimento et al., 2016; Vriesmann & Petkowicz, 2013) Also, the presence of rhamnose, which was identified only in trace amounts in PFPP, was associated with lower viscosity and weaker gels, as it may induce kinks in the galacturonan structure, thus interfering in the macromolecular organization required to form a gel network (Oakenfull, 1991) It is also reported that the presence of neutral side chains and the low molecular weight pectin may weaken the gel strength once less junction zones would be formed (BeMiller, 2019; Axelos & Thibault, 1991) Interestingly, PFPP molecular weight was lower (53 kDa) compared to other HMP sources (> 100 kDa) and also demonstrated a homogeneous elution profile (HPSEC-MALLS), when compared to other HMP sources 3.4 Scanning electron microscopy of PFPP sample The scanning electron microscopy of PFPP was also performed (Fig 4) It is possible to observe a delicate and smooth material According to Einhorn-Stoll (2018) homogeneous surface of pectin particles can promote water uptake and immobilization, moreover the author argues that amorphous particles allow fast water permeation and reaching of hydrophilic groups, compared to crystalline ones As it can be seen in Fig 4, the whole structure resembles more amorphous, and that may explain PFPP behaviour when water was added, with fast uptake and swelling In sum, these images show that PFPP presents a porous homogeneous structure that may explain its high uptake and swelling in water Finally, it is important to note that PFPP had similar yield (20 % yield) compared to the main sources of commercial pectin worldwide, i.e apple pomace and citrus pectin, which yields approximately 4–21 % and 9–33 %, respectively (Abboud et al., 2019; Chan et al., 2017) Taken together, all the results presented herein reinforce that passion fruit peel could be a novel source of commercial HMP, with distinguished rheological properties Conclusion PFPP extracted in this study, which is an HMP, demonstrated shearthinning non-Newtonian rheological behaviour distinct from other HMPs, as no alteration in pH and addition of co-solute (sucrose) was required for PFPP in order to form weak gels Moreover, the addition of sucrose increased its apparent viscosity, however, not so intensively as observed for other HMPs, for which the addition of sucrose played a crucial role in gelation mechanism PFPP samples seems to maintain their weak gels profiles under pasteurization-like process, with or without sucrose addition PFPP had a yield comparable to other commercial pectins, which in turn enhance its feasibility to use as an alternative source of HMP Moreover, there is a growing well-being trend among consumers and PFPP could fit well these demands since it didn’t require sugar or chemical alterations to form gel, besides its well-known health Carbohydrate Polymers 246 (2020) 116616 K.Y Abboud, et al properties, prebiotic and DF potential Lastly, PFPP may be a feasible option as a rheological modifier agent, with reduced environmental impact and bioactive properties Lamothe, L M., Srichuwong, S., Reuhs, B L., & Hamaker, B R (2015) Quinoa (Chenopodium quinoa W.) and amaranth (Amaranthus caudatus L.) provide dietary fibres high in pectic substances and xyloglucans Food Chemistry, 167, 490–496 Lapasin, R., & Pricl, S (1995) Rheology of polysaccharide systems In R Lapasin, & S Pricl (Eds.) Rheology of industrial polysaccharides: Theory and applications (pp 251– 293) London: Black Academic & Professional Lewis, M., & Heppell, N (2000) Continuous thermal processing of foods pasteurization and UHT sterilization Gaithersburg, Maryland Lopes da Silva, J A., & Rao, M A (2007) Pectins: Structure, funcionality, and uses In A M Stephen, G O Phillips, & P A Williams (Eds.) Food polysaccharides and their applications (pp 353–412) Taylor & Francis Macagnan, F T., Santos, L R., Roberto, B S., Moura, F A., Bizzani, M., & Silva, L P (2015) Biological properties of apple pomace, orange bagasse and passion fruit peel as alternative sources of dietary fibre Bioactive Carbohydrates and Dietary Fibre, 6(1), 1–6 May, C D (1990) Industrial Pectins: Sources, production and applications Carbohydrate Polymers, 12, 79–99 May, C D (2000) Pectins In G O Phillips, & P A Williams (Eds.) Handbook of hydrocolloids (pp 169–188) Cambridge, England: Woodhead Publishing Limited Min, B., Lim, J., Ko, S., Lee, K., Lee, S H., & Lee, S (2011) Environmentally friendly preparation of pectins from agricultural byproducts and their structural/rheological characterization Bioresource Technology, 102, 3855–3860 Nascimento, G E., Simas-Tosin, F F., Iacomini, M., Gorin, P A J., & Cordeiro, L M C (2016) Rheological behaviour of high methoxyl pectin from the pulp of tamarillo fruit (Solanum betaceum) Carbohydrate Polymers, 139, 125–130 Oakenfull, D G (1991) The chemistry of High-methoxyl pectins High In R Walter (Ed.) The chemistry and technology of pectin Oakenfull, D G., & Scott, A (1984) Hydrophobic interaction in the gelation of high methoxyl pectins International Journal of Food Sciences and Nutrition, 49, 1093–1098 Ramos, A T., Cunha, M A L., Sabaa-Srur, A U O., Pires, V C F., Cardoso, M A A., Diniz, M F F M., et al (2007) Use of Passiflora edulis f flavicarpa on cholesterol reduction Brazilian Journal of Pharmacognosy, 17(4), 592–597 Rao, M A (2007) Flow and functional models for rheological properties of fluid foods In M A Rao (Ed.) Rheology of fluid and semisolid foods (pp 27–58) Boston, MA: Springer US Schramm, G (2006) Reologia e Reometria: Fundamentos teóricos e práticos (2 ed.) São Paulo: Artliber Editora Ltda Shaw, M T., & MacKnight, W J (2005) Introduction to polymer viscoelasticity (3rd edition) Hoboken, NJ: John Wiley & Sons, Inc Silva, J A L., & Gonỗalves, M P (1994) Rheological study into the ageing process of high methoxyl pectin/sucrose aqueous gels Carbohydrate Polymers, 24(4), 235–245 Simas-Tosin, F F., Barraza, R R., Petkowicz, C L O., Silveira, J L M., Sassaki, G L., Santos, E M R., et al (2010) Rheological and structural characteristics of peach tree gum exudate Food Hydrocolloids, 24, 486–493 Sousa, A G., Nielsen, H L., Armagan, I., Larsen, J., & Sørensen, S O (2015) The impact of rhamnogalacturonan-I side chain monosaccharides on the rheological properties of citrus pectin Food Hydrocolloids, 47, 130–139 Souza, J S., & Gerum, A F A A (2017) Aspectos econômicos da produỗóo maracujỏ no Brasil In T G Junghans, & O N Jesus (Eds.) Maracujỏ: Do cultivo comercializaỗóo (pp 9–14) Brasília, DF: Embrapa 2017 Strưm, A., Schuster, E., & Goh, S M (2014) Rheological characterization of acid pectin samples in the absence and presence of monovalent ions Carbohydrate Polymers, 113, 336–343 Thakur, B R., Singh, R K., & Handa, A K (1997) Chemistry and uses of pectin — A review Critical Reviews in Food Science and Nutrition, 37(1), 47–73 Vriesmann, L C., & Petkowicz, C L O (2013) Highly acetylated pectin from cacao pod husks (Theobroma cacao L.) forms gel Food Hydrocolloids, 33, 58–65 Vriesmann, L C., Silveira, J L M., & Petkowicz, C L O (2010) Rheological behaviour of a pectic fraction from the pulp of cupuassu (Theobroma grandiflorum) Carbohydrate Polymers, 79(2), 312–317 Yapo, B M (2011) Pectic substances: From simple pectic polysaccharides to complex pectins – A new hypothetical model Carbohydrate Polymers, 86, 373–385 Yapo, B M., & Koffi, K L (2006) Yellow passion fruit rinds - a potential source of lowmethoxyl pectin Journal of Agricultural and Food Chemistry, 54, 2738–2744 Yoo, S., Fishman, M L., Hotchkiss, A T., & Lee, H G (2006) Viscometric behavior of high-methoxy and low-methoxy pectin solutions Food Hydrocolloids, 20, 62–67 Zhong, Q., & Daubert, C R (2013) Food rheologyHandbook of farm, dairy and food machinery engineering (2nd ed.) Norwich, NY: William Andrew Publishing CRediT authorship contribution statement Kahlile Youssef Abboud: Investigation, Writing - original draft, Visualization Marcello Iacomini: Supervision, Funding acquisition Fernanda Fogagnoli Simas: Writing - review & editing, Supervision Lucimara M.C Cordeiro: Writing - review & editing, Supervision, Funding acquisition, Project administration Acknowledgements This research was supported by CNPq foundation (Process 404717/ 2016-0 and 310332/2015-0) and by a fellowship granted to K Y Abboud (Process 1564544) provided by CAPES The authors are grateful to Electron Microscopy Center of the Federal University of Paraná for the scanning electron microscopy experiments References Abboud, K Y., Luz, B B., Dallazen, J L., Werner, M F P., Cazarin, C B B., Junior, M R M., et al (2019) Gastroprotective effect of soluble dietary fibres from yellow passion fruit (Passiflora edulis f flavicarpa) peel against ethanol-induced ulcer in rats Journal of Functional Foods, 54, 552–558 Adetunji, L R., Adekunle, A., Orsat, V., & Raghavan, V (2017) Advances in the pectin production process using novel extraction techniques: A review Food Hydrocolloids, 62, 239–250 Albuquerque, M A C., Albuquerque, C., Livitc, R., Beresd, C., Bedania, R., LeBlanc, A M., et al (2019) Tropical fruit by-products water extracts as sources of soluble fibres and phenolic compounds with potential antioxidant, anti-inflammatory, and functional properties Journal of Functional Foods, 52, 724–733 Alexandrou, A N., McGilvreay, T M., & Burgos, G (2001) Steady Herschel–Bulkley fluid flow in three-dimensional expansions Journal of Non-Newtonian Fluid Mechanics, 100(1), 77–96 Barbieri, S F., Amaral, S C., Ruthes, A C., Petkowicz, C L O., Kerkhoven, N C., Silva, E R A., et al (2019) Pectins from the pulp of gabiroba (Campomanesia xanthocarpa Berg): Structural characterization and rheological behaviour Carbohydrate Polymers, 214, 250–258 BeMiller, J N (2019) Carbohydrate chemistry for food scientists (3rd ed.) Woodhead Publishing and AACC International Press (Charpter 15) Canteri, M H., Scheer, A., Petkowicz, C., Ginies, C., Renard, C., & Wosiacki, G (2010) Physicochemical composition of the yellow passion fruit pericarp fractions and respective pectic substances Journal of Food and Nutrition Research, 49(3), 113–122 Chan, S Y., Choo, W S., Young, D J., & Loh, X J (2017) Pectin as a rheology modifier: Origin, structure, commercial production and rheology Carbohydrate Polymers, 161, 118–139 Colodel, C., Vriesmann, L C., & Petkowicz, C L O (2019) Rheological characterization of a pectin extracted from ponkan (Citrus reticulata blanco cv ponkan) peel Food Hydrocolloids, 94, 326–332 Corrêa, E M., Medina, L., Barros-Monteiro, J., Valle, N O., Sales, R., Magalães, A., et al (2014) The intake of fiber mesocarp Passion Fruit (Passiflora edulis) lowers levels of triglyceride and cholesterol decreasing principally insulin and leptin The Journal of Aging Research & Clinical Practice, 3(1), 31–35 de Queiroz, M S R., Janebro, D I., Cunha, M A L., Medeiros, J S., Sabaa-Srur, A U O., Diniz, M F F M., et al (2012) Effect of the yellow passion fruit peel flour (Passiflora edulis f flavicarpa deg.) in insulin sensitivity in type diabetes mellitus patients Nutrition Journal, 11, 89–96 de Souza, C B., Jonathan, M., Saad, S M I., Schols, H A., & Venema, K (2018) Characterization and in vitro digestibility of byproducts from Brazilian food industry: Cassava bagasse, orange bagasse and passion fruit peel Bioactive Carbohydrates and Dietary Fibre, 16, 90–99 Doran, P M (2013) Fluid flow In P M Doran (Ed.) Bioprocess engineering principles (pp 201–254) United kingdom: Elsevier Einhorn-Stoll, U (2018) Pectin-water interactions in foods – From powder to gel Food Hydrocolloids, 78, 109–119 Englyst, K N., Liu, S., & Englyst, H N (2007) Nutritional characterization and measurements of dietary carbohydrates European Journal of Clinical Nutrition, 61(1), S19–S39 Kowalska, H., Czajkowska, K., Cichowska, J., & Lenart, A (2017) What’s new in biopotential of fruit and vegetable by-products applied in the food processing industry Trends in Food Science & Technology, 67, 150–159 Web reference https://www.marketwatch.com/press-release/global-pectin-market-2019-globalindustry-size-share-business-growth-revenue-trends-global-market-demandpenetration-and-forecast-to-2024-2019-08-27 Accessed March 19, 2020 ... behaviour of high methoxyl pectin from the pulp of tamarillo fruit (Solanum betaceum) Carbohydrate Polymers, 139, 125–130 Oakenfull, D G (1991) The chemistry of High- methoxyl pectins High In R... for the rheological properties of high methoxyl pectins (May, 1990; Thakur, Singh, & Handa, 1997), the main objective of this work was to evaluate the rheological properties of the high methoxyl. .. properties of passion fruit pectins Yapo and Koffi (2006) evaluated the gelling ability and viscoelastic properties of a low methoxyl pectin extracted from passion fruit peel from Ivory Coast, while