Escalating the technical bounds for the production of cellulose-aided peach leathers: From the benchtop to the pilot plant

This contribution falls within the context of sustainable functional materials. We report on the production of fruit leathers based chiefly on peach pulp, but combined with hydroxypropyl methylcellulose (HPMC) as binding agent and cellulose micro/nanofibrils (CMNF) as fillers.

Carbohydrate Polymers 245 (2020) 116437 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Escalating the technical bounds for the production of cellulose-aided peach leathers: From the benchtop to the pilot plant T Giuliana T Francoa,b,1, Caio G Otonia,c,1,*, Beatriz D Lodia, Marcos V Lorevicea, Márcia R de Mourad, Luiz H.C Mattosoa,* a Nanotechnology National Laboratory for Agriculture (LNNA), Embrapa Instrumentation, Rua XV de Novembro, 1452, São Carlos, SP 13560-979, Brazil PPGQ, Department of Chemistry, Federal University of São Carlos, Rod Washington Luís, km 235, São Carlos, SP 13565-905, Brazil c Department of Materials Engineering, Federal University of São Carlos, Rod Washington Luís, km 235, São Carlos, SP 13565-905, Brazil d Department of Physics and Chemistry, FEIS, São Paulo State University, Av Brasil, 56, Ilha Solteira, SP 15385-000, Brazil b ARTICLE INFO ABSTRACT Keywords: Prunus persica Continuous casting Edible film Ternary mixture design Response surface methodology Food packaging This contribution falls within the context of sustainable functional materials We report on the production of fruit leathers based chiefly on peach pulp, but combined with hydroxypropyl methylcellulose (HPMC) as binding agent and cellulose micro/nanofibrils (CMNF) as fillers Increased permeability to moisture (from 0.9 to 5.6 g mm kPa−1 h−1m−2) and extensibility (from 10 to 17%) but reduced mechanical resistance (67–2 MPa) and stiffness (1.8 GPa–18 MPa) evidenced the plasticizing effect of peach pulp in HPMC matrix, which was reinforced by CMNF A ternary mixture design allowed building response surfaces and optimizing leather composition The laboratory-scale leather production via bench casting was extended to a pilot-scale through continuous casting The effect of scaling up on the nutritional and sensory features of the peach leather was also depicted The herein established composition-processing-property correlations are useful to support the large-scale production of peach leather towards applications both as packaging materials and as nutritional leathers Introduction Strategies towards increased shelf life have become increasingly demanded due to the complex food supply chain faced by today’s society, involving long distances and periods of transportation and storage Packaging systems have gained prominence due to their role as physical hurdles against food dehydration and spoilage Ongoing is also the trend of replacing petrochemical building blocks of non-biodegradable materials by rapidly renewable raw materials for biodegradable packaging (Ahmadzadeh & Khaneghah, 2019) This drives one’s attention not only to what comes from Nature, but also to what goes back to the environment Edible packaging – i.e., that comprising exclusively food-grade components, regardless of processing (Cerqueira, 2019) – stands out in this context, particularly for single-use applications, as waste is either not generated or readily biodegradable Should such materials be also intended to protect foodstuffs, these must perform suitably from the physical-mechanical standpoint, as extensively demonstrated for edible coating and self-standing films based on naturally occurring polysaccharides and polypeptides (Atarés & Chiralt, 2016; Dehghani, Hosseini, & Regenstein, 2018) Fruits and vegetables have been increasingly exploited as edible film-forming matrices, in combination with natural polymer or by themselves thanks to their typically high loads of carbohydrates and/or proteins (Otoni et al., 2017) Depending on the formulation and processing conditions, self-standing edible layers having fruit pulp or puree as main ingredient can behave rheomechanically like thermoplastics – bioplastics – or present a leathery consistency – fruit leathers (Otoni et al., 2017) Both approaches may not only contribute to solving the aforementioned sustainability related issues, but also to human health because of their nutritional load, as well as to consumer perception due Abbreviations: ANOVA, analysis of variance; CMNF, cellulose micro/nanofibrils; DPPH, 2,2-diphenyl-1-picrylhydrazyl; HPMC, hydroxypropyl methylcellulose; LFF, leather-forming formulations; MW, molecular weight; RDI, recommended daily intakes; RH, relative humidity; Trolox, 6-hydroxy-2,5,7,8-tetramethylchroman-2carboxylic acid; WVP, water vapor permeability ⁎ Corresponding authors at: Nanotechnology National Laboratory for Agriculture (LNNA), Embrapa Instrumentation, Rua XV de Novembro, 1452, São Carlos, SP 13560-970, Brazil E-mail addresses: gtfranco@estudante.ufscar.br (G.T Franco), otoni@unicamp.br (C.G Otoni), beatrizdlodi@hotmail.com (B.D Lodi), marcos.lorevice@lnnano.cnpem.br (M.V Lorevice), marcia.aouada@unesp.br (M.R.d Moura), luiz.mattoso@embrapa.br (L.H.C Mattoso) These authors contributed equally https://doi.org/10.1016/j.carbpol.2020.116437 Received February 2020; Received in revised form April 2020; Accepted May 2020 Available online 24 May 2020 0144-8617/ © 2020 Elsevier Ltd All rights reserved Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al to their unique sensory features The possibilities of using overripe produce (Aguirre-Joya et al., 2018) or even side streams from its processing (Otoni, Lodi et al., 2018) make such a novel class of materials further appealing by valorizing typically underutilized resources, which in turn is expected to culminate in diminished food waste It is noteworthy that, owing to their low water activity levels, fruit leathers may be taken as dehydrated foods and ought to be stable as far as microbial spoilage as long as they are protected from moisture (Otoni et al., 2017) From the shelf life standpoint, while fruit leathers are ideal to wrap dry foodstuffs within also dry environments, these can be suitably used in humid atmospheres provided they are further enclosed within a high-barrier secondary packaging, but they are less likely to serve as primary packaging for moist foods In line, the exploitation of underutilized resources is also expected to reduce production costs and to add value to otherwise discarded raw materials Also related with the production costs of bioplastics and fruit leathers is the material-forming method itself, which is traditionally carried out in batch-mode solvent casting, process that involves laboratory scale, long drying times, and low yields – herein referred to as bench casting (de Moraes, Scheibe, Sereno, & Laurindo, 2013; Otoni et al., 2017) The continuous analogue of bench casting has been demonstrated to remarkably increase the yield of edible layers made up of fruits and vegetables (Munhoz et al., 2018; Otoni, Lodi et al., 2018), even though maintaining the properties remains challenging because of the relatively low thermal stability of some of their constituents From the mechanical standpoint, specifically, should fruit-only bioplastics perform poorly, these can be combined to other food-grade matrices and fillers, such as lignocellulosics – e.g., hydroxypropyl methylcellulose (HPMC), a nonionic cellulose ether that is widely known for its film-forming ability (Hay et al., 2018) and for being generally recognized as safe (FDA; GRAS Notice No GRN 000213, 2007) and approved as a food additive (US FDA, 21 CFR 172.874, 2011; and European Union, EPCD No 95/2/EC, 1995) Among these biorenewables, cellulose micro/nanofibrils (CMNF) denote efficient fillers for mechanically reinforcing edible bioplastics (Valencia, Nomena, Mathew, & Velikov, 2019; Viana, Sá, Barros, Borges, & Azeredo, 2018) In the context presented above, this contribution is devoted to fruit leathers comprising peach pulp as main component and HPMC and CMNF, herein exploited as binding and reinforcing agents, respectively The role played by each of these components on the physical-mechanical properties of the resulting materials was fully depicted Finally, this study also set out to scale up the production of the peach leathers from bench casting to its continuous equivalent, as well as to either confirm or refute the hypothesis that the leather-forming protocol influences the key properties of such materials, including nutritional and sensory aspects USA) was used in all experiments 2.2 Leather production via bench casting The components listed above were mechanically stirred at 1500 rpm for 30 under vacuum (500 mmHg) into leather-forming formulations (LFF) that were allowed to rest under vacuum for another 30 to remove bubbles before being spread with uniform thickness onto a poly(ethylene terephthalate) sheet, where they were dried at room temperature and 50 ± 10% relative humidity (RH) for 24 h Dried leathers were peeled from the casting surface and equilibrated at room temperature and 50% RH for at least 48 h in a desiccator containing saturated magnesium nitrate solution before used for testing 2.3 Leather production via continuous casting Leathers were also produced in a continuous fashion on a KTF-B lamination system (Werner Mathis AG, Switzerland) that comprised four main steps, namely: 1, feeding: the LFF was poured on a Mylar (DuPont Teijin Films U.S Ltd., USA) conveyor belt; 2, lamination: the LFF was forced through a gap between the polyester substrate and a knife into a 1.50-mm-thick, 26-cm-wide wet layer; 3, drying: the wet LFF layer was conveyed through an infrared pre-drying stage (at ca 45 °C and 0.10 m⋅min−1 for 30 cm) and two convective drying stages (at 120 °C and 0.10 m min−1 for 92 cm each); and 4, winding The feedingto-winding distance and time were m and 30 min, respectively Prior to any testing, dried leathers were stored as described previously 2.4 Experimental design, optimizations, and scale up Peach pulp, HPMC, and CMNF were combined at different proportions according to a ternary mixture design (Table S1) The weight ratio (dry basis) of each component ranged from to 1, their weighted contributions together adding up to Bench casting (Section 2.2) was used at this stage Tensile strength ( T ), Young’s modulus (E), and elongation at break ( B ) were determined by tensile assay on a DMA Q800 dynamic-mechanical analyzer (TA Instruments, Inc., USA), calculated by Eq to Eq 3, and taken as dependent variables for optimization purposes T (1) = F / A0 B=[(LB L0 )/ L0]·100 E = lim / L L L0 (2) (3) Where F is the maximum load, L is the extension (at a given point: no index; at the beginning of the assay: index 0; at break: index B), σ is the stress at a given point, and A0 is the initial cross-sectional area, the latter considering sample thickness, which was measured with a digital micrometer (Mitutoyo Corp., Japan) by averaging five random measurements The load cell was 18 N and the stretching rate was 0.1% min−1 The response variables were used to build response surfaces To investigate the isolated effect of peach pulp on the mechanical and barrier properties of the leathers, 2.5, 5.0, or 7.5% (w/v) of peach pulp was mixed with 2% (w/v) of HPMC in water The LFF were converted into leathers by bench casting (Section 2.2) and characterized as described in Sections 2.5 and 2.6 Finally, to assess the effect of scaling up leather production on its key properties, the optimum LFF (XPP = 0.85, XHPMC = 0.15; further discussion below) was also processed through continuous casting (Section 2.3), and the nutritional and sensory properties of the continuously and bench-cast leathers were compared Materials and methods 2.1 Materials Pasteurized peach pulp (De Marchi, Brazil), HPMC Methocel® E4M (CAS no 9004-65-3; The Dow Chemical Company, Brazil) – comprehensively characterized elsewhere [degree of substitution: 1.9; Mw: ca 350,000 g mol−1 (Otoni, Lorevice, Moura, & Mattoso, 2018)] – and 2,2diphenyl-1-picrylhydrazyl (DPPH) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, or Trolox (Sigma-Aldrich Co LLC, USA) were used as received Microcrystalline cellulose Sigmacell® Type 50 (CAS no 9004-34-6; Sigma-Aldrich Brasil Ltd, Brazil) – ζ potential: -1.0 ± 0.4 mV; apparent particle size: 1.6 ± 0.9 μm; crystallinity index: 62 ± 2% (Otoni, Carvalho et al., 2018) – was dispersed in water at 1% (w/v) without any pretreatment or purification and high-pressure microfluidized (Microfluidizer® M-110 P; Microfluidics Corp., USA) for seven cycles at 138 MPa into CMNF – ζ potential: -30 to -24 mV; apparent particle size: 160−250 nm; crystallinity index: 70–75% (Otoni, Carvalho et al., 2018) Ultrapure water (Barnstead Nanopure Diamond, 2.5 Mechanical properties The leathers were submitted to uniaxial tensile assay on a DL3000 Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al Fig Surface response plots for the mechanical properties of biocomposites comprising different weight ratios of peach pulp (PP), hydroxypropyl methylcellulose (HPMC), and cellulose micro/nanofibrils (CMNF) universal testing machine (EMIC Equipamentos e Sistemas de Ensaio Ltda., Brazil) equipped with a 10-kgf load cell At least six leather specimens per treatment, shaped in accordance with ASTM D882−18, were stretched at 10 mm min−1 from an initial length (L0 ) of 100 mm until rupture The mechanical attributes T , B , and E were calculated using Eq (1), Eq (2), and Eq (3), respectively Williams, Cuvelier, and Berset (1995) Briefly, 0.1 mL of different dilutions (in methanol) of the supernatant was mixed with 3.9 mL of a 0.0024% (w/v) solution of DPPH, also in methanol The mixtures were kept in the dark at room temperature for 30 before having their absorbances at 515 nm measured on a UV-1601PC spectrophotometer (Shimadzu Co., Japan) Leather-free methanol and DPPH solutions were used as blank and control, respectively An analytical curve was adjusted by varying the concentrations of Trolox – a standard antioxidant analogous to vitamin E – from 80 to 800 mg L−1 and used to quantitatively express the antioxidant capacity of the leathers, in μg of Trolox equivalent per g of sample (μg g−1) 2.6 Barrier to water vapor The water vapor permeability (WVP) of the leathers was measured in accordance with the modification of ASTM E96−80 proposed by McHugh, Avena-Bustillos, and Krochta (1993) In brief, at least four leather specimens per treatment were fixed onto the edges of poly (methyl methacrylate) capsules with circular openings of 5.1 cm in diameter, serving as semi-permeable barriers between an inner high-RH environment and a chamber at 30 ± °C and 30 ± 2% RH The capsules were weighed periodically to determine WVP 2.8 Content of minerals The content of minerals in the fruit leathers was determined by atomic absorption spectrometry Continuously and bench-cast leathers (1−2 g, measured accurately) were digested in a mixture of nitric acid P.A (10 mL), hydrochloric acid P.A (5 mL), and 30 vol hydrogen peroxide (3 mL) on a Kjeldahl digester (model SL-25/40, Solab Equipamentos para Laboratório Ltda., Brazil) at 140 °C for 24 h and then filtered through filter paper into 50-mL volumetric flasks that were further completed with ultrapure water The resulting solutions were analyzed on a PinAAcle 900 T spectrometer (PerkinElmer, Inc., USA), with flame and radiation sources at specific wavelengths to determine the following minerals: Fe, 248.33 nm; K, 766.49 nm; Mg, 285.21 nm; 2.7 Antioxidant capacity Continuously and bench-cast leathers (1−2 g, measured accurately) were dipped in 20 mL 99.8% pure methanol at °C for 24 h The methanolic extracts were centrifuged (Rotina 380 R, Andreas Hettich GmbH & Co KG, Germany) for 10 at 15 °C and 10,000 rpm and had their antioxidant capacities determined as described by Brand3 Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al Ca, 422.67 nm; Mn, 279.48 nm; and Na, 589.00 nm Analytical curves were previously built with standard solutions of each of these minerals and used for the quantitative interpretation of the results The runs were carried out in triplicates tensile behavior of the peach leathers The surface response plots resulting from the ternary mixture design are presented in Fig The statistical procedure allowed establishing models that were efficient in fitting the acquired mechanical data The regression coefficients of such models are presented in Table S2 The response surface plots elucidate the role played by each of the components: HPMC serves as binding agent and leather-forming matrix, higher HPMC contents being accompanied by also higher tensile strengths; CMNF act as fillers for mechanical reinforcement, thus leading to stronger leathers; and peach pulp, introduced as the major functional ingredient, but from the mechanical standpoint behaving as a plasticizer by increasing leather extensibility and decreasing its resistance and stiffness This mapping strategy allows one to engineer the mechanical properties of materials made up of such a system without the need for further testing Importantly, we demonstrate the possibility of producing biocomposite leathers with varying mechanical performances by simply altering the composition of the LFF, ranging from rubbery self-standing layers – suitable for applications as edible leathers, for instance – all the way to stiff sheets – suitable for e.g food packaging Because we targeted at leather that are functional – and as preliminary tests showed that neither HPMC nor CMNF themselves have antioxidant activity – but still provide sufficient mechanical strength to be used as self-supporting layers, the LFF chosen for the further steps comprised 85 wt.% peach pulp and 15 wt.% HPMC This approach is illustrated in Fig It is worth stressing out that, should superior mechanical properties be required for a given application, the established relationships can be used to alter the LFF and produce materials with tailored mechanical performance 2.9 Colorimetric parameters The color of the fruit leathers was determined on a CR-400 digital colorimeter (Konica Minolta Sensing, Inc., Japan) The brightness (L*) and the chromaticity parameters a* (red-to-green) and b* (yellow-toblue) were determined in at least three random positions along the leather surfaces The LFF served as reference for calculating the total color difference (ΔE) by Eq 4, wherein the subscript indexes L and LFF refer to leather and leather-forming formulations, respectively Yellowness index (YI) and whiteness index (WI) were calculated through Eq and Eq 6, respectively E = [(LL* * LLFF )2 + (aL* YI = 142.86 bL* LL* WI = 100 [(100 * aLFF ) + (bL* * bLFF )2]0.5 (4) (5) LL* ) + aL*2 + bL*2]0.5 (6) 2.10 Statistical treatment of data Quantitative data were submitted to analysis of variance (ANOVA) at 5% of significance followed by regression analysis or Tukey test at the same level of significance, as suitable Mechanical data were fitted to quadratic regression models according to the mixture design The importance of model components was examined by ANOVA (also at 5%), and nonsignificant effects were disregarded from the models that were used to plot response surfaces 3.2 On the role of peach pulp on HPMC matrix Because peach pulp and HPMC were selected as the constituents of the peach leathers, the effect of mixing them at different proportions was further investigated as far as mechanical and water barrier properties (Fig 3) All of the evaluated properties were affected (P < 0.05) by composition Peach pulp itself formed a continuous layer that was easily detachable from the casting surface, although with extremely low stiffness and resistance while with high extensibility As expected, higher peach pulp contents led to leathers featuring lower resistance and stiffness, but higher extensibility and permeability to moisture This Results and discussion 3.1 On the optimization of leather formulation Physical-mechanical cohesion and integrity were herein taken as the primary technical requirements for fruit leathers to be suitably used as self-standing layers, application that would be prevented otherwise This was the rationale for relying the optimization procedures upon the Fig Left: formulations of peach leathers using hydroxypropyl methylcellulose (HPMC) as binder and of biocomposites comprising cellulose micro/nanofibrils (CMNF) as fillers; right: leather-forming formulation before (top) and after (bottom) drying either on lab- (bench casting) or pilot-scale (continuous casting) The insets show dried leather specimens shaped for tensile assays Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al Fig Mechanical properties and water vapor permeability (WVP) of peach leathers made up of the combination, at different weight ratios (dry basis) of peach pulp and hydroxypropyl methylcellulose Dotted lines indicate fittings to actual data points, whose equations are presented as Supplementary Material (Eq S1 to Eq S4) drying the LFF indeed boosted water removal: whereas the dried leather was detached from the bench casting substrate 24 h after the deposition of the LFF, the feeding-to-winding time in the continuous casting was only 30 min, i.e., a significant 48-time reduction This was allowed by the infrared pre-drying stage and the convective drying at higher temperatures As reported by Otoni, Lodi et al (2018), who produced carrot-based biocomposites using the same apparatus and conditions, this aspect is important because ca 75 m2 would be needed to produce such an area of leather through bench casting, number that would be reduced to ca m2 for continuous casting This discrepancy gets increasingly enlarged as the production volume increases, corroborating the relevance of scaling up the production of fruit leathers in the direction of large-scale industrial operations As important as the yield is the maintenance of the key features of fruit leathers, which are to be preserved even after harsher processing conditions In this context, the antioxidant capacity, color, and content of minerals were compared in the continuously and bench-cast leathers The antioxidant capacity of both leathers as well as their contents of the minerals K, Na, Mg, Ca, Fe, and Mn are presented in Table The processing method had either low or no influence on the mineral content, which was somehow expected due to the high thermal stability of these compounds Considering the recommended daily intakes (RDI) of these minerals in adult diets, as defined by the Brazilian Health Regulatory Agency (ANVISA) through Resolution RDC No 269, the produced leathers, regardless of the processing method, can be classified as sources – 100 g of leather provide more than 15% of the RDI – of the macronutrient potassium and the micronutrient manganese Additionally, these leathers are classified as having high contents – 100 g of leather provides more than 30% of the RDI – of the micronutrient iron Also importantly, it is classified as having low sodium content – 100 g of leather comprises less than 120 mg of sodium As for the antioxidant capacity, the processing at higher temperatures led to a reduction, but both continuously and bench-cast leathers were highly antioxidant This is also expected as fruits and vegetables are overall known to have several antioxidant compounds, including phenolics, flavonoids, terpenes, sterols, saponins, glycosinolates, and carotenoids, being often associated with reduced risk of cardiovascular disease, cancer, arteriosclerosis, and other diseases related to the aging process and induced by the formation of free radicals (Du, AvenaBustillos, Breksa, & McHugh, 2014) Through different mechanisms, Table Antioxidant capacity (AC), contents of minerals, and their recommended daily intakes (RDI) in peach leathers produced on laboratory and pilot scales Mineral Bench casting /mg 100 g−1 Continuous casting /mg 100 g−1 RDI /mg 100 g−1 K Na Mg Ca Fe Mn AC (μg Trolox g−1) 995 ± 53a 48.5 ± 0.2a 32.5 ± 0.1a 17 ± 1a 4.9 ± 0.1a 0.66 ± 0.02a 2920 ± 21b 920 ± 34a 53.4 ± 0.2b 35.7 ± 0.1a 17.7 ± 0.1a 4.8 ± 0.1a 0.64 ± 0.01a 2555 ± 58a 4700 – 260 1000 14 2.3 – ab Within a row, different mean ± standard deviation values (P < 0.05) are followed by different superscript letters effect, which is typical of plasticizers, had already been reported after the incorporation other fruit pulps and purees (e.g., guava and papaya) into HPMC films (Lorevice, Moura, de, Aouada, & Mattoso, 2012; Lorevice, Moura, de, & Mattoso, 2014) This effect can be attributed to low-molecular weight (MW) compounds that are naturally found in fruits, such as mono, di, and oligosaccharides (Espitia et al., 2014) As a matter of fact, 100 g fresh peach has been shown to contain 5.2–8.8 g sucrose – MW: 342.3 g⋅mol−1 – ca 1.2 g of glucose – MW: 180.2 g mol−1 – and 1.1–1.4 g of fructose – MW: 180.2 g⋅mol−1 (Cascales, Costell, & Romojaro, 2005) These low-MW components can easily accommodate themselves between HPMC chains – MW ca 330,000 g mol−1 for the E4M grade –, separating them apart In the context of mechanical performance during uniaxial tensile assay, this plasticizing behavior lessens the level of intermolecular interaction and allows adjacent HPMC chains to flow more freely one over another Regarding barrier to moisture, separating HPMC chains increases the intermolecular volume and reduces the tortuosity of the path followed by the permeant, in this case water vapor Water molecules can therefore diffuse more easily from the high- to the low-RH environments, culminating in higher WVP values 3.3 On the effect of scaling up leather production Peach leathers were successfully produced through both bench and continuous casting procedures (Fig 2) The pilot-scale approach of Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al these compounds are able to stop oxidative reactions in their early stages by the accepting free radicals, donating hydrogen atoms to serve as free radical acceptors, or chelating metals that catalyze oxidative reactions (Eỗa, Machado, Hubinger, & Menegalli, 2015; Reis et al., 2015) In peach, specifically, high levels of carotenoids, flavonoids, anthocyanins, and hydroxycinnamate have been reported (Gil, TomásBarberán, Hess-Pierce, & Kader, 2002; Zhao et al., 2015) The RDI of antioxidant compounds for benefiting human health is from 0.75 to 0.90 g of Trolox, and fruit and vegetable intake accounts for 0.3−0.4 g Trolox d−1 (Prior & Cao, 2000), corroborating the relevance of having leathers as an extra form of fruit intake In addition to the benefits to human health, the antioxidant capacity of bioplastics, and therefore of fruit leathers, can also be advantageous in the case of food preservation, since oxidation reactions of organic molecules represent one of the main mechanisms of food spoilage: besides causing nutritional – by the loss of vitamins and essential fatty acids – and sensory depreciation – by the occurrence of oxidative rancidity –, toxic compounds can be produced (Reis et al., 2015) Color was taken as an indicator of the sensory quality of the peach leathers, as it is indeed one of the most important attributes affecting food appearance and having a pronounced influence on consumers' perception The colorimetric parameters of the leathers are presented in Table Simply drying the LFF into leathers, regardless of the method, increased the values of the three coordinates of the CIELab scale, behavior which can be attributed to the concentration of chromophore compounds The similar total color difference values – which takes the three colorimetric coordinates into account – between the continuously and bench-cast leathers, in relation to the precursor LFF, suggest that the overall color variation was not affected by the processing protocol When the coordinates are analyzed as isolated variables, however, the scaled up leathers were darker than those produced by bench casting, as indicated by the higher L* values and whiteness index of bench cast leathers This is attributed to non-enzymatic browning reactions, like the Maillard reaction, which involves the interaction between reducing carbohydrates (mainly fructose and glucose in the case of peach) and amino acids and/or proteins upon heating, culminating in the production of dark-colored compounds such as melanoidins Peach darkening kinetics has been shown to be temperature-dependent, being faster at higher temperatures, as well as to involve carotenoid degradation during heat treatment, leading to the depreciation of the yellowish coloration and the enhancement of the reddish hue (Ávila & Silva, 1999) Indeed, the herein produced peach leathers attained a stronger red color when processed at 120 °C – indicated by the higher a* value – but yellowing did not follow the same trend It is important mentioning that bench casting peach leather could also cause enzymatic browning reactions, but the previous pasteurization of the peach pulp is expected to inactivate the oxidative enzymes (e.g., peroxidase and polyphenoloxidase) responsible for such processes Finally, although high mechanical and barrier performances were not targeted for the herein produced peach leathers, it is noteworthy that the WVP of bench (7.7 ± 0.9 g mm kPa−1 h−1 m−2) and continuously (6.8 ± 0.2 g mm kPa−1 h−1 m−2) cast leathers was not affected (P > 0.05) by the leather-forming method The tensile resistance (3.5 ± 0.1 to 2.6 ± 0.1 MPa), stiffness (44 ± to 36 ± MPa), and extensibility (14.4 ± 0.3 to 12.6 ± 0.6%), conversely, were slightly reduced when the casting process was scaled up Table Colorimetric parameters of peach leather-forming formulations (LFF) and leathers produced on laboratory (bench casting) and pilot (continuous casting) scales Declaration of Competing Interest Parameter L* a* b* ΔE Yellowness index Whiteness index LFF Bench casting a 35.1 ± 0.3 0.1 ± 0.0a 13.7 ± 0.3a – 55.7 33.7 c 55 ± 14 ± 1b 37 ± 1b 33.7 97.6 39.7 Conclusions The pilot-scale production of peach leathers was herein demonstrated to be feasible in terms of physical-mechanical, nutritional, and sensory properties The interdependency among leather composition, leather-forming parameters, and leather properties was also elucidated, confirming the roles played by peach pulp as the main component, HPMC as binding agent, and CMNF as filler In particular, peach pulp presented a typical plasticizing behavior, decreasing both resistance and stiffness while increasing extensibility and WVP of peach leathers CMNF, on the other hand, were efficient in providing mechanical reinforcement The continuous casting approach was successful in removing the dispersant medium of the LFF in a significantly faster fashion, boosting yield and productivity while maintaining the key characteristics of the final materials, refuting the initial hypothesis The mineral content, for instance, was not impacted, while the continuously cast leathers presented an even more reddish aspect than their benchcast analogues, increasing the association of the former with in natura peach Both leathers presented high antioxidant capacity, although slightly reduced in the leather processed at higher temperatures Altogether, our results help pave the route for the large-scale production of fruit-based materials towards industrial applicability both as packaging materials and as nutritional leathers Funding This work was supported by the São Paulo Research Foundation (FAPESP) [grant numbers 2013/14366-7, 2014/23098-9, and 2019/ 06170-1], National Council for Scientific and Technological Development (CNPq) [grant numbers 303796/2014-6, 312530/2018-8, and 800629/2016-7], Coordination for the Improvement of Higher Education Personnel (CAPES) [grant numbers 33001014005D‐6 and 88882.332747/2019-01], and Ministry of Science, Technology, and Innovation (MCTI/SISNANO) [grant number 402287/2013-4] CRediT authorship contribution statement Giuliana T Franco: Writing - original draft, Investigation Caio G Otoni: Conceptualization, Investigation, Writing - original draft Beatriz D Lodi: Investigation Marcos V Lorevice: Investigation, Writing - original draft Márcia R de Moura: Supervision, Writing review & editing Luiz H.C Mattoso: Conceptualization, Funding acquisition, Project administration, Supervision, Writing - review & editing None Continuous casting Acknowledgements 48 ± 1b 20.8 ± 0.5c 36 ± 1b 33.2 106.8 33.6 The authors are thankful for the financial support of FAPESP (grants no 2013/14366-7, no 2014/23098-9, and no 2019/06170-1), CNPq (grants no 303796/2014-6, no 312530/2018-8, and no 800629/ 2016-7), SISNANO/MCTI (grant no 402287/2013-4), CAPES (grants no 33001014005D‐6 and 88882.332747/2019-01), FINEP, and Embrapa AgroNano research network The gracious donation of HPMC samples by The Dow Chemical Company is also acknowledged abc Within a row, different mean ± standard deviation values (P < 0.05) are followed by different superscript letters Carbohydrate Polymers 245 (2020) 116437 G.T Franco, et al Appendix A Supplementary data G W (2018) Improved hydroxypropyl methylcellulose (HPMC) films through 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