Agro-food By-products Research Articles

Ultrasound‐assisted extraction of pomegranate peel antioxidants: A green process to obtain a meat preservative

As an agro-food by-product, pomegranate peel is a potential source of bioactive compounds with preservative properties. Ultrasound-assisted extraction (UAE) is a green extraction method that is useful in increasing extraction yields and reducing extraction time without using toxic solvents. This study aimed to optimize the UAE of a pomegranate peel for its use as a preservative using water as the solvent, maximizing its antioxidant potential for its particular application to chicken burgers. A Box–Behnken design was applied using extraction time, extraction temperature, and ultrasound amplitude as independent variables. The response surface methodology (RSM) results showed that the highest concentration of the phenolic compound is obtained at amplitude—50%, temperature—38°C, and time—15 min. The extracts with RSM conditions at a concentration of 0.8% indicated that the extracted preservative exerts the ability to delay meat oxidation on days 1, 2, 4, and 7, even better than ascorbic acid. Practical applications The waste and elimination of agro-industrial by-products generate significant environmental impacts and critical economic losses. Today, a sustainable paradigm it seeks to add extra value to these by-products by giving them a new application in the production chains, thus favoring the circular economy. The ultrasound-assisted process is an excellent tool to obtain green compounds that cover the recent concern from the industry and consumers for healthier foods. In this case, the application of the pomegranate peel extract is presented as an alternative to synthetic preservatives due to its great antioxidant capacity.

Effects of wet brewers grains on fermentation quality and in vitro ruminal digestibility of mixed silage prepared with corn stalk, sweet potato peel and dried apple pomace in southeast China.

The effects of wet brewers grains (WBG) on fermentation quality, chemical composition and in vitro ruminal digestibility of mixed silages prepared with corn stalk, dried apple pomace and sweet potato peel were evaluated. A mixture of corn stalk, sweet potato peel and dried apple pomace (50/30/20) was ensiled with 0, 10%, 20% and 30% WBG on a fresh weight (FW) basis for 1, 3, 5, 7, 14 and 30 days respectively. The results showed that the application of WBG increased (p < 0.05) lactic acid, acetic acid and total volatile fatty acids contents, and decreased (p < 0.05) pH, dry matter, water-soluble carbohydrates content and ammonia-nitrogen/total nitrogen during ensiling. The pH in all silages was below 4.03 during ensiling. Treating with WBG increased (p < 0.05) crude protein content, and decreased (p < 0.05) neutral detergent fibre, acid detergent fibre, cellulose and hemicellulose content after 30 days of ensiling. After 72 h of incubation, cumulative gas production, potential gas production and in vitro crude protein digestibility increased (p < 0.05) with the increasing proportions of WBG. However, in vitro digestibility of dry matter and neutral detergent fibre, and metabolisable energy were similar in all silages. The 20% and 30% WBG-treated silages showed better fermentation quality and greater or higher in vitro digestibility, which were indicated by greater or higher (p < 0.05) lactic acid content, in vitro crude protein digestibility, and lower (p < 0.05) pH, ammonia-nitrogen/total nitrogen ratio as compared with the control. Therefore, ensiling agro-food by-products with at least 20% WBG were recommended for improving fermentation quality.

Effects of brewers’ spent grains on fermentation quality, chemical composition and in vitro digestibility of mixed silage prepared with corn stalk, dried apple pomace and sweet potato vine

The experiment was conducted to evaluate the effects of brewers’ spent grains (BSG) on the fermentation quality, chemical composition and in vitro parameters of mixed silage prepared with corn stalk, dried apple pomace and sweet potato vine. In the experiment, a ternary mixture of corn stalk, sweet potato vine and dried apple pomace (50/30/20) was ensiled with 0%, 10%, 15% and 20% BSG on a fresh weight (FW) basis for 1, 3, 5, 7, 14 and 30 days, respectively. The application of BSG significantly (p<.05) increased lactic, acetic and total volatile fatty acids content, and significantly (p<.05) decreased pH, lactic acid/acetic acid, ammonia nitrogen, dry matter and water-soluble carbohydrates content during ensiling. None or tiny amounts of propionic and butyric acid were detected in all silages. Compared with the control, higher (p<.05) Flieg points, crude protein content and lower (p<.05) neutral detergent fibre, acid detergent fibre, cellulose and hemicellulose content were found in BSG-treated silages on day 30 of ensiling. After 72 h of incubation, the application of BSG significantly (p<.05) increased the cumulative gas production, potential gas production, in vitro dry matter, crude protein digestibility and metabolisable energy. The 20% BSG silages had better fermentation quality and higher in vitro digestibility, as indicated by higher lactic acid content, in vitro dry matter, crude protein digestibility, metabolisable energy, lower pH, and lower ammonia nitrogen content than other silages. The application of 20% BSG was recommended to ensure good quality silages. Highlights Ensiling in the form of mixed silages is a good way to consume largely agro-food by-products. Reducing the energy waste and environmental pollution caused by high-quantity agro-food by-products. 20% brewers’ spent grains application had positive effects on in vitro parameters.

A Tara Gum/Olive Mill Wastewaters Phytochemicals Conjugate as a New Ingredient for the Formulation of an Antioxidant-Enriched Pudding.

Olive mill wastewater, a high polyphenols agro-food by-product, was successfully exploited in an eco-friendly radical process to synthesize an antioxidant macromolecule, usefully engaged as a functional ingredient to prepare functional puddings. The chemical composition of lyophilized olive mill wastewaters (LOMW) was investigated by HPLC-MS/MS and 1H-NMR analyses, while antioxidant profile was in vitro evaluated by colorimetric assays. Oleuropein aglycone (5.8 μg mL−1) appeared as the main compound, although relevant amounts of an isomer of the 3-hydroxytyrosol glucoside (4.3 μg mL−1) and quinic acid (4.1 μg mL−1) were also detected. LOMW was able to greatly inhibit ABTS radical (IC50 equal to 0.019 mg mL−1), displaying, in the aqueous medium, an increase in its scavenger properties by almost one order of magnitude compared to the organic one. LOMW reactive species and tara gum chains were involved in an eco-friendly grafting reaction to synthesize a polymeric conjugate that was characterized by spectroscopic, calorimetric and toxicity studies. In vitro acute oral toxicity was tested against 3T3 fibroblasts and Caco-2 cells, confirming that the polymers do not have any effect on cell viability at the dietary use concentrations. Antioxidant properties of the polymeric conjugate were also evaluated, suggesting its employment as a thickening agent, in the preparation of pear puree-based pudding. High performance of consistency and relevant antioxidants features over time (28 days) were detected in the milk-based foodstuff, in comparison with its non-functional counterparts, confirming LOWM as an attractive source to achieve high performing functional foods.

EFFECT OF SOME AGRO-INDUSTRIAL RESIDUES ON MYCELIAL GROWTH AND PRODUCTION OF LIGNOCELLULOLYTIC ENZYMES BY A FUNGUS NATIVE TO ALGERIAN FOREST

Valorization of agricultural and agro-food by-products by fermentation constitutes a very interesting biotechnological approach for the production of lignocellulolytic enzymes. This work was carried out to reveal the effect of some lignocellulosic materials on the mycelial growth and lignocellulolytic enzymes production by Bjerkandera adusta BRFM 1916. The strain showed ABTS- and guaiacol-oxidation activities. The optimal temperature for mycelial growth was 28 °C. The maximum growth rate of this fungus was achieved on wheat bran (2.08 ± 0.05 cm day-1), followed by barley bran, with a significant reduction of 6.73%. Several agricultural lignocellulosic residues were used as substrates for enzymes production. All the data indicated differential utilization of the various materials by the fungus. The selected fungus produced good CMCase (690 ± 0.066 UL-1) and β-Glu (253 UL-1) activities on wheat bran and orange peels, respectively. A high level of MnP activity (449.21 ± 3.44 UL-1) was obtained on wheat bran.

Impact of some local organic by-products on Acheta domesticus growth and meal production

The house cricket Acheta domesticus is one of the species of major interest as alternative protein source for humans in the recent research of sustainable and nutritious sources of food. However, grain feeds, feed for poultry and soybean still represent common source of feeds for the insect industry. The aim of this study was to evaluate the influence of some agro-food by-products on the growth parameters of the crickets and the nutritional composition of the final cricket meal. Our study included five by-products (maize grain distiller, fruits and vegetables, grape marc, and two brewery’s wastes), while hen feed was used as a control diet. Substrates were analysed for their microbiological contamination prior to be provided to crickets. No Listeria and Salmonella were detected, but high microbial counts were observed. Crickets grown on the given by-products showed significant differences on the insect’s weight starting from the third week. High mortality was observed on all substrates, except on maize distiller and the control diet. The final cricket meal showed a similar protein content (66-68% as is), while the lipid content was higher in the meal from cricket reared on maize distiller (22% as is). Finally, microbiological and chemical analyses on the cricket meals did not show safety concerns for the consumers. The by-products studied, except maize grain distiller, did not support an optimal cricket rearing, but more studies are necessary to identify a mix-formulation meeting the cricket nutritional requirements.

Pomegranate Byproduct Extracts as Ingredients for Producing Experimental Cheese with Enhanced Microbiological, Functional, and Physical Characteristics

Pomegranate peel and mesocarp, considered as wastes of fruit processing, are rich sources of beneficial phytochemicals, including hydrolyzable tannins and flavonoids, with proven antimicrobial and antioxidant activity, which can be employed for improving the overall quality of food products. In the present study, extracts from pomegranate peel (PPW) and mesocarp (PMW) were obtained through a water extraction method and evaluated for in vitro antimicrobial activity and polyphenol content. The two extracts were then added during the cheese-making process in order to create a new functional cheese with improved microbiological and physico-chemical characteristics. Antimicrobial in vitro assays evidenced a substantial efficacy of both extracts against Staphylococcus aureus, which often causes staphylococcal food poisoning outbreaks linked to the consumption of raw milk cheeses and artisanal cheeses. For this reason, a simulated cheese contamination was carried out in order to assess if pomegranate extracts can exert antimicrobial activity towards this pathogen even when incorporated into the cheese matrix. Milk enriched with pomegranate extracts (PPW and PMW) was used to produce two different experimental cheeses, which were then evaluated for yield, polyphenol content, and microbiological as well as physico-chemical traits throughout the refrigerated storage. Despite the low concentration of the extracts, the treated cheeses showed an increase in firmness and a slight decrease in S. aureus counts, of more than one log unit in comparison to the control cheese, for up to 12 d of cold storage. Such results support the reuse of agro-food byproducts, in substitution to chemical food preservatives, as the key to a circular economy.

Using High-Pressure Technology to Develop Antioxidant-Rich Extracts from Bravo de Esmolfe Apple Residues.

Bravo de Esmolfe (BE) is a traditional Portuguese apple highly appreciated by consumers due to its peculiar flavor and aroma. This apple contains higher concentration of phenolic compounds than other cultivars and is thus considered a rich source of antioxidants. Its sensorial and functional properties have attracted farmers’ associations to increase BE production. However, a large quantity of apples is wasted due to storage/transportation procedures that impact BE’s quality attributes. In this work, we applied high-pressure extraction methodologies to generate antioxidant-rich fractions from BE residues aiming at adding high value to these agro-food by-products. We performed a first extraction step using supercritical CO2, followed by a second extraction step where different CO2 + ethanol mixtures (10–100% v/v) were tested. All experiments were carried out at 25 MPa and 50 °C. Extracts were characterized in terms of global yield, phenolic content and antioxidant activity using chemical (ORAC, HOSC, HORAC) and cell-based assays (CAA). We demonstrated that, although the pressurized 100% ethanol condition promoted the highest recovery of phenolic compounds (509 ± 8 mg GAE/100 g BE residues), the extract obtained with 40% ethanol presented the highest CAA (1.50 ± 0.24 µmol QE/g dw) and ORAC (285 ± 16 µmol TEAC/g dw), as well as HOSC and HORAC values, which correlated with its content of epicatechin and procyanidin B2. Noteworthy, this fraction inhibited free radical production in human neurospheroids derived from NT2 cells, a robust 3D cell model for neuroprotective testing.

Valorization of agro-food by-products and their potential therapeutic applications

Agro-food industries generate a huge amount of fruit and vegetable wastes. These residues are composed by structural parts (leaves, peels, pulps, seeds, roots and stems) after the extraction of their juices, and they are rich in bioactive compounds such polyphenols, protein, carbohydates, fibre, lignin, lipids and minerals. Therefore, these wastes constitute a source of bioactive compunds and their valorization leads to a circular economy in which industry and society benefit. Between the component of the residues, polyphenols compounds may contribute to prevent or treated cancer, neurodegenerative and cardiovascular diseases, among others. The aim of this work was the study of the potential therapeutic effect of fruit and vegetable extracts (peach, apple, cucumber and red pepper) obtained by ultrasounds, on different lines of cancer cells (colon, liver and breast) and on oxidative stress in a healthy colon. The results showed that extracts rich in polyphenols had an antiproliferativeeffect against tumor cells and their action was improved by encapsulation in maltodextrin. Encapsulation also increased the protection against oxidative stress in intestinal cells. This study opened the gate to use the extracts from fruit and vegetable wastes as pharmaceutical excipients, food additives, nutraceutical products or functional foods for therapeutic purposes and prevention of diseases related to oxidative stress.

Deep Eutectic Solvents for the Extraction of Bioactive Compounds from Natural Sources and Agricultural By-Products

In this work, a review about the applicability of eutectic solvents, mainly deep eutectic solvents (DES) and natural deep eutectic solvents (NADES), for the extraction of bioactive compounds from natural products has been carried out. These alternative solvents have shown not only to have high extraction yields but also to be environmentally friendly, exhibiting very low or almost no toxicity, compared to conventional organic solvents. The last trends and main extraction methods that have been most widely used in studies using these emerging solvents have been reviewed, as well as the varied natural sources in which they have been used, including agro-food by-products. Besides the toxicity, biodegradability of these solvents is reviewed. Likewise, different reported bioactivity tests have been included, in which extracts obtained with these ecological solvents have been tested from antioxidant activity analysis to in vivo studies with rats, through in vitro cytotoxicity tests.

Recent Trends in Sustainable Remediation of Pb-Contaminated Shooting Range Soils: Rethinking Waste Management within a Circular Economy

Soil metal contamination in recreational shooting ranges represents a widespread environmental problem. Lead (Pb) is the primary component of traditional ammunition, followed by metalloids such as antimony (Sb) and arsenic (As). Lead-based bullets and pellets deposited on the soil surface are subject to steady weathering; hence, metal(loid)s are released and accumulated in the underlying soil, with potential adverse consequences for ecosystem function and human health. Amongst the currently available environmentally-safe technologies for the remediation of metal-contaminated soils, chemical immobilization is recognized as the most practical and cost-effective one. This technology often uses inorganic and organic amendments to reduce metal mobility, bioavailability and toxicity (environmental benefits). Likewise, amendments may also promote and speed up the re-establishment of vegetation on metal-affected soils, thus facilitating the conversion of abandoned shooting ranges into public green spaces (social benefit). In line with this, the circular economy paradigm calls for a more sustainable waste management, for instance, by recycling and reusing by-products and wastes in an attempt to reduce the demand for raw materials (economic benefit). The objective of this manuscript is to present a state-of-the-art review of the different industrial and agro-food by-products and wastes used for the remediation of metal-contaminated shooting range soils.

On the Use of Biobased Waxes to Tune Thermal and Mechanical Properties of Polyhydroxyalkanoates-Bran Biocomposites.

In this work, processability and mechanical performances of bio-composites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) containing 5, 10, and 15 wt % of bran fibers, untreated and treated with natural carnauba and bee waxes were evaluated. Wheat bran, the main byproduct of flour milling, was used as filler to reduce the final cost of the PHBV-based composites and, in the same time, to find a potential valorization to this agro-food by-product, widely available at low cost. The results showed that the wheat bran powder did not act as reinforcement, but as filler for PHBV, due to an unfavorable aspect ratio of the particles and poor adhesion with the polymeric matrix, with consequent moderate loss in mechanical properties (tensile strength and elongation at break). The surface treatment of the wheat bran particles with waxes, and in particular with beeswax, was found to improve the mechanical performance in terms of tensile properties and impact resistance of the composites, enhancing the adhesion between the PHBV-based polymeric matrix and the bran fibers, as confirmed by predictive analytic models and dynamic mechanical analysis results.

Microwave assisted extraction of inositols for the valorization of legume by-products

Currently there is great interest in exploitation of agrofood by-products, such as those from legumes, as source of bioactive ingredients. To that aim, characterization of cyclitol and sugar composition of pods and seeds from different legume species has been carried out. A green Microwave Assisted Extraction (MAE) method was optimized for extraction of bioactive inositols, and both pod and seed yields were compared with those obtained by conventional reflux extraction. A subsequent Saccharomyces cerevisiae treatment was also evaluated for removal of interfering coextracted sugars.myo-Inositol was present in all legume pods and seeds and galactinol in most seeds. chiro-Inositol was found in soybean and basul, whereas outstanding pinitol concentrations were only detected in soybean. The optimized MAE method provided extracts rich in pinitol from soybean pods (41.5–58.0 mg g−1) and seeds (5.3–7.5 mg g−1). Removal of 97% of interfering sugars in MAE soybean pod extracts was achieved by yeast treatment.

Tailoring the surface properties and flexibility of starch-based films using oil and waxes recovered from potato chips byproducts

Agrofood byproducts may be exploited as a source of biomolecules suitable for developing bioplastic materials. In this work, the feasibility of using starch, oil, and waxes recovered from potato chips byproducts for films production was studied. The recovered potato starch-rich fraction (RPS) contained an amylopectin/amylose ratio of 2.3, gelatinization temperatures varying from 59 to 71 °C, and a gelatinization enthalpy of 12.5 J/g, similarly to a commercial potato starch (CPS). Despite of its spherical and oval granules identical to CPS, RPS had a more amorphous structure and gave rise to low viscous suspensions, contradicting the typical B-type polymorph crystal structure and sluggish dispersions of CPS, respectively. When used for films production, RPS originated transparent films with lower roughness and wettability than CPS-based films, but with higher stretchability. In turn, when combined with RPS and CPS, oil or waxes recovered from frying residues and potato peels, respectively, allowed to develop transparent yellowish RPS- and CPS-based films with increased surface hydrophobicity, mechanical traction resistance, elasticity, and/or plasticity. Therefore, potato chips industry byproducts revealed to have thermoplastic and hydrophobic biomolecules that can be used to efficiently develop biobased plastics with improved surface properties and flexibility, opening an opportunity for their valorization.

A Pilot Screening of Agro-Food Waste Products as Sources of Nutraceutical Formulations to Improve Simulated Postprandial Glycaemia and Insulinaemia in Healthy Subjects.

The control of glucose homeostasis is the main goal for both the prevention and management of diabetes and pre-diabetes. Numerous drugs are available, despite their side effects. This is constantly leading people to be inclined to natural alternative treatments. Evidence indicates antioxidant-based nutraceuticals as an optimal tool for the glycaemic control. Currently, a great interest has been focused on the valorisation of agro-food by-products as sources of bioactive compounds including polyphenols. In this sense, we tested the efficacy of novel nutraceutical products based on polyphenolic extract from nectarines (NecP), tomato peels (TP), and olive leaves (EOL) on glycaemic and insulinemic responses. The three formulations contained, respectively, 0.007 mg abscisic acid (ABA)/g, 0.5 mg carotenoids/g, and 150 mg oleuropein/g. Twenty healthy subjects consumed a regular glucose solution (RG) or a treatment beverage (TB) obtained by mixing RG with the individual formulations (TB NecP, TB EOL, and TB TP), separately, and on different days. All three formulations significantly lowered the 30 min glucose plasma peak (p < 0.05 for all); similarly, NecP and TP also significantly lowered the 30 min insulin plasma peak (p < 0.05 for all). These results may lead to the hypothesis of a formulation of a multi-component nutraceutical with a synergistic efficacy for the glycaemic control.

Unravelling the Biological Potential of Pinus pinaster Bark Extracts.

Natural compounds from agro-food by-products have fostered interest in food industries. The aim of this study was to unravel potential uses for Pinus pinaster bark extracts (PBE). As functional features of this type of extracts are usually attributed to phenolic compounds, the extraction process was studied. Different PBEs were achieved, with high content in phenolic compounds, using different water/ethanol combinations as a solvent. These PBEs were chemically characterized, and their bioactivity and in vitro cell viability were evaluated. Extracts obtained with hydroethanolic solvents had higher content in phenolic and flavonoid compounds. All the PBEs presented high antioxidant, antibacterial and antihyperglycemic activities. Moreover, PBEs have low cytotoxicity and a selective activity against cancer cells as these were negatively affected. These features may allow the extracts to be used in food formulation and processing (as preservatives, antioxidants or bioactive ingredients), but they showed also potential for the pharmaceutical or nutraceutical sectors.

Establishment of Acid Hydrolysis by Box–Behnken Methodology as Pretreatment to Obtain Reducing Sugars from Tiger Nut Byproducts

Carbohydrate-rich byproducts may be used as a growth substrate for microalgae. The tiger nut, compared to other tubers, has higher carbohydrate content, which mostly remain in the byproduct after the production of tiger nut milk (“Horchata”). The aim of this study is the optimization of a hydrolysis pre-treatment in tiger nut byproduct to obtain reducing sugars, objective framed in the European SUSPUFA (Sustainable production of health-promoting n-3 LC-PUFA using agro-food industry by-products through microalgae) Project. Two experimental 4-factor Box–Behnken designs (acid concentration (N), temperature (°C), time (min) and ratio acid/sample) were carried out with 27 experiments to optimize chemical hydrolysis conditions with H2SO4 and H3PO4 in duplicate. The sugars were determined by the Schoorl method and the extracts obtained by the optimal conditions were analyzed by high-performance liquid chromatography (HPLC). Protected designation of origin (PDO) and non-protected designation of origin (n-PDO) tiger nut byproducts were characterized by physicochemical methods. The validity of the experimental designs was confirmed by ANOVA. The optimum sugar values were obtained with H2SO4 2 N at 85 °C, 60 min and ratio 60 and H3PO4 21 N at 90 °C, 60 min and ratio 60. Glucose and xylose were the sugars detected in the hydrolyzed samples. In conclusion, almost 50% of the total carbohydrates present in the tiger nut byproduct were hydrolyzed to reducing sugars.

Mechanical cell disruption of mustard bran suspensions for improved dispersion properties and protein release.

Mustard bran, a by-product of mustard production, is still rich in valuable compounds. The high-pressure homogenization treatment was tested as a mechanical cell disruption (MCD) technique to unlock valuable intracellular compounds. An aqueous suspension of mustard bran was treated by shear mixing, followed by high-pressure homogenization at different pressure levels (50-150 MPa) and number of passes (1-10), and using different homogenizing systems. The moderate-intensity treatment (up to 100 MPa and 3 passes) can deliver significant changes in the mustard bran suspension, inducing (a) a more homogeneous and smooth appearance due to the disruption of individual cells, (b) a better structuring ability in the suspension, through the increase in viscosity and storage and loss moduli G' and G'', as well as (c) a remarkable enhancement of protein release, up to 72% of total proteins. The controlling factor in the extent of MCD was found to be the specific energy transferred to the mustard bran suspensions, whereas no significant differences were recorded when varying the homogenization system. The MCD process of mustard bran, based on its physical treatments using only water as a suspension medium, can be regarded as a safe, clean and environmentally friendly technology platform, which contributes to reaching the zero-waste concept by transforming agro-food by-products into value-added ingredients, with enhanced functionality and bioactive content.

Valorization of corn cob for the obtention and purification of endoglucanase produced by SSF

Abstract Agro-food by-products contain valuable nutrients which are wasted. In this work, solid-state fermentation (SSF) was carried out using corn cob as substrate for endoglucanase production. The radial growth of three fungal strains -Trichoderma harzianum T104, Aspergillus niger GH1 and Aspergillus niger NRRL3- was analyzed in order to select the most appropriate. Radial growth data were analyzed with a mixed linear model for longitudinal data and no statistically significant differences were found between both A. niger strains. Endoglucanase was separated from the extract of A. niger GH1 by fast protein liquid chromatography (FPLC).The highest endoglucanase activity was detected in fraction number three collected from FPLC corresponding to 72 h of SSF. Seven bands in a range from 24 to 50 kDa, which correspond to endoglucanase from fungal extract, were detected by zymogram analysis. According to protein quantification performed by the ImageJ software, 85% of the proteins present in the samples collected by FPLC corresponded to endoglucanase proteins. The purified endoglucanase retained about 100% of its catalytic activity at 30 °C and 50 °C and was stable in a pH range between 4.00-6.00. These properties make this isolated enzyme suitable for industrial applications such as the saccharification process for bioethanol production.

Valorisation Approach for the Soybean By-Product Okara Using High Hydrostatic Pressure

Okara is a perishable, cheap and abundant by-product derived from soybean after extracting the soluble fraction for tofu or soybean drink, mainly known as soymilk, production. Nowadays, Okara is mostly discarded: landfill and incineration, but a useful alternative for valorisation would be to use it as a valuable source of dietary fibre. However, it presents low soluble dietary fibre (SDF) content responsible for prebiotic and anti-carcinogenic effects, so an easy industrial transformation to maximize its SDF content would be most interesting for this purpose. Different approaches can be used to increase SDF content, such as chemical or enzymatic treatments with food-grade enzymes at atmospheric pressure, but these conventional methods present some disadvantages as that the chemical procedures are pollutant and the extractions normally are incomplete, and the enzymatic methods could be expensive to scale-up. On the other hand, currently, consumers are demanding for safer, more natural and minimally-processed foods. This request has led researchers and manufacturers to develop new technologies, and within these, high hydrostatic pressure (HHP) is one of the top-10 most popular emerging technologies applied in the field of food science. The effect of HHP, and more recently, the combined effect of HHP and enzymatic treatment on okara by-product have been studied, showing that this novel approach, should also be considered in order to stabilise other agro-food byproducts -due to their perishable character- as well as to improve the functionality of the rich-ininsoluble dietary fibre from vegetable residues.