Okara: A soybean by-product as an alternative to enrich vegetable paste

Investigating the physicochemical characteristics and importance of insoluble dietary fiber extracted from legumes: An in-depth study on its biological functions

Legumes are widely appreciated for their abundant reserves of insoluble dietary fiber, which are characterized by their high fiber content and diverse bioactive compounds. Insoluble dietary fiber in leguminous crops is primarily localized in the structural cell walls and outer integument and exhibits strong hydrophilic properties that enable water absorption and volumetric expansion, resulting in increased food bulk and viscosity. This contributes to enhanced satiety and accelerated gastrointestinal transit. The benefits of legume insoluble dietary fiber extend to its notable antioxidant, anti-inflammatory, and anti-cancer properties, as well as its ability to modulate the composition of the intestinal microbiota, promoting the growth of beneficial bacteria while suppressing the proliferation of harmful pathogens, thereby promoting optimal intestinal health. It is highly valued as a valuable thickening agent, stabilizer, and emulsifier, contributing to the texture and stability of a wide range of food products.

Formulation development and characterization of plant-based alternatives to pâté using forest ingredients

Due to the expanding global population and environmental concerns about meat production from livestock, there is a great demand for alternative ingredients. Beech achene (BA) and sessile oak acorn (SOA) were recently proposed as protein- and carbohydrate-rich novel food ingredients. This study used their roasted kernels to develop and characterize four formulations of spreadable vegetable paste (with 10% BAK, 10% SOAK, 5% SOAK + 5% BAK, and control-just with roasted sunflower kernel). The substitution of sunflower kernel with 10% BAK caused a decrease in the energy value of vegetable paste, while 10% SOAK and 5% SOAK + 5% BAK, an increase. Syneresis was higher in formulations with forest ingredients, most notably in those containing BAK. The SOAK also caused a decrease in the pH of vegetable pastes that included it. All forest formulations had a large total colour difference compared to the control sample, driven by its intensity decrease (less in that with BAK than in the other two). The acceptance rate was reasonable for all formulations, although the overall score was significantly lower (slightly liked) in the vegetable paste formulated only with BAK than in the others (moderately liked); thus, the consumer's purchase intention too (only 4.9% for that with 10% SOAK). Formulation with 10% BAK had a higher hardness, adhesiveness, gumminess, and chewiness than the others, while that with the 5% SOAK and 5% BAK mixture showed the most robust network structure. In conclusion, BA and SOA kernels are suitable for manufacturing plant-based alternatives to pâté if used in proper concentrations.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05852-7.

Valorization and food applications of okara (soybean residue): A concurrent review

Agriculture waste is rising continuously across the globe due to enormous industrial, food processing, and household activities. Proper valorization of this waste could be a promising source of various essential bioactive and functional ingredients. Okara is a major residue produced as result of soybean processing and has a rich nutritional profile. The nutritional profile of okara is affected by the processing conditions, variety, pre-treatment, post-production treatments, and processing techniques. Owing to the high fibers, lipids, proteins, and bioactive components, it is being used as an essential industrial ingredient in various food processing industries. The prebiotic potential and nutritional profile can be increased by various techniques, that is, enzymatic, chemical, biotransformation, high-pressure microfludization, and fermentation. The prebiotic potential of okara makes it suitable as a therapeutic agent to prevent a variety of metabolic disorders such as diabetes, obesity, hypercholesterolemia, and hyperlipidemia. The current review highlights the structural, nutritional, functional, therapeutic, and industrial applications of okara.

Okara-Enriched Gluten-Free Bread: Nutritional, Antioxidant and Sensory Properties

The aim of this study was to produce an eco-innovative gluten-free bread with a pleasant taste and a unique formulation that includes the highest quality grains and pseudocereals (buckwheat; rice; and millet); and okara; a by-product of soy milk production. The mixture of pseudocereal and cereal flour contained buckwheat flour 45%, rice flour 33%, and millet flour 22%. Three gluten-free breads; each containing different contents of gluten-free flour (90%, 80%, and 70%, respectively); okara (10%, 20%, and 30%, respectively); and a control sample (without okara); were prepared and subjected to sensory evaluation. The okara-enriched gluten-free bread with the highest sensory score was selected for further analysis of physico-chemical (total proteins; total carbohydrates; insoluble fiber; soluble fiber; sugars; total lipids; saturated fatty acids; and salt) and functional properties (total phenolic content and antioxidant properties). The highest sensory scores were obtained for 30% okara-enriched gluten-free bread including taste; shape; odor; chewiness; and cross-section properties; classifying this bread in the category of very good quality and excellent quality (mean score 4.30 by trained evaluators and 4.59 by consumers). This bread was characterized by a high content of dietary fiber (14%), the absence of sugar; low content of saturated fatty acids (0.8%), rich source of proteins (8.8%) and certain minerals (e.g.,; iron; zinc); and low energy value (136.37 kcal/100g DW). Total phenolic content was 133.75 mgGAE/100g FW; whereas ferric reducing power; ABTS radical cation; and DPPH radical scavenging activity were 119.25 mgAA/100g FW; 86.80 mgTrolox/100g FW; and 49.92 mgTrolox/100g FW; respectively. Okara addition in gluten-free bread production enables the formulation of high-nutritive; good antioxidative; low-energy bread; and better soy milk waste management.

Almond okara as a valuable ingredient in biscuit preparation

BACKGROUND

The okara is the water-insoluble residue derived from the production of plant-based beverages, including almond milk. Information on almond okara is scarce, with no scientific references. In the present study, the almond okara was characterized and used to replace wheat flour at 15%, 25% and 35% for biscuit preparation.

RESULTS

The contents of protein, lipid and dietary fiber of almond okara were 140.08, 421.16 and 407.90 g kg^-1 dry matter, respectively. The lipid fraction of almond okara showed contents of triacylglycerol oligopolymers and oxidized triacylglycerols of 0.12 and 5.14 g kg^-1 , respectively, which were significantly lower than the levels observed in the sunflower oil used in the formulation of biscuits. Consequently, the biscuits containing okara showed a content of triacylglycerol oligopolymers lower than that of control biscuits. The texture analysis revealed that the addition of the okara at 25% and 35% caused a significant increase in biscuit hardness and a reduction of the brittleness, compared to the control. The sensory evaluation confirmed these data, highlighting the slight impact of the almond okara on the almond odor, taste and flavor attributes.

CONCLUSION

Almond okara is a valuable by-product that can be easily used as an ingredient for biscuit preparation, exploiting its fiber, protein and lipid content to improve the nutritional value of food, with a limited impact on the sensory properties. © 2022 Society of Chemical Industry.

Phytochemicals Derived from Agricultural Residues and Their Valuable Properties and Applications

Billions of tons of agro-industrial residues are produced worldwide. This is associated with the risk of pollution as well as management and economic problems. Simultaneously, non-edible portions of many crops are rich in bioactive compounds with valuable properties. For this reason, developing various methods for utilizing agro-industrial residues as a source of high-value by-products is very important. The main objective of the paper is a review of the newest studies on biologically active compounds included in non-edible parts of crops with the highest amount of waste generated annually in the world. The review also provides the newest data on the chemical and biological properties, as well as the potential application of phytochemicals from such waste. The review shows that, in 2020, there were above 6 billion tonnes of residues only from the most popular crops. The greatest amount is generated during sugar, oil, and flour production. All described residues contain valuable phytochemicals that exhibit antioxidant, antimicrobial and very often anti-cancer activity. Many studies show interesting applications, mainly in pharmaceuticals and food production, but also in agriculture and wastewater remediation, as well as metal and steel industries.

Enhanced production of fibrous bacterial cellulose in Gluconacetobacter xylinus culture medium containing modified protein of okara waste

In Gluconacetobacter xylinus cultivation for bacterial nanocellulose production, agro-industrial wastes, soybean residual okara, okara extracted protein, and modified okara protein, were used as a protein source. In comparison with homogenized raw okara and protein extracted from raw okara, acetic-acid modified protein provided the higher cellulose yield (2.8 g/l at 3 %w/v protein concentration) due to the improved protein solubility in the culture medium (89 %) and smaller particle size (0.2 μm) leading to facile uptake by the bacteria. Importantly, pH of the culture medium containing the modified protein measured before and after the cultivation was similar, suggesting the buffering capacity of the protein. Nanocellulose fibers were then produced densely in the network of hydrogels with high crystallinity nearly 90 %. Based on the results, economic constraints around nanocellulose production could be alleviated by valorization of okara waste, which provided enhanced sustainability.

Characterisation of a High Fibre Flour Prepared from Soy Milk By-Product and Its Potential Use in White Wheat Bread

The commercial production of soy milk renders a large quantity of wet soybean by-product (SMB), which is typically dumped, incinerated, or partially used as animal fodder. This wet SMB has a high moisture content that is rich in nutritional and biologically active compounds. This study aimed to characterise the composition and properties of a flour milled from SMB dried at 100 °C (SMB100) and assess its possible application as a fibre substitute in white bread. The results showed that SMB100 has high levels of dietary fibre (40.6%) and protein (26.5%). It also contains high levels of saponins (31.4 mg/g) and isoflavones (698.0 µg/g). SMB100 has a light-yellow colour with low moisture content and water activity (8.2% and 0.55, respectively). The results also indicated that replacement of wheat flour with SMB100 at 10 or 12.5% by flour weight negatively impacted the raising volume, density, and texture of white bread. Alternatively, substituting wheat flour with 5% of SMB100, did not significantly impact the physical properties of white bread, while significantly improving its dietary fibre content in comparison with the control, revealing that SMB100 is a potential substitute of wheat flour for improvement of dietary fibre in bread. Future studies are needed to optimise bread formulation and improve the processing condition which produces quality white bread with high dietary fibre using SMB100.

Isolation and Molecular Characterization of Processed Soybean Waste for the Development of Synbiotic Yogurt

Soybean has good nutritional and functional properties, which are essential for human physiology. Okara, a residue from soybean processing industries has a distinct profile of nutrients and phytochemicals. Therefore, the current study was planned to investigate the functional importance of okara. In the first phase of this study, okara was isolated from soybean and characterized in terms of protein, fat, ash, soluble dietary fiber, and insoluble dietary fiber. Furthermore, the okara flour was characterized using FT-IR (Fourier transform infrared spectroscopy), and micrograph images were obtained using SEM (scanning electron microscope). In the second phase of study, synbiotic (prebiotics + probiotics) yogurt was prepared with 3% concentrations of okara. Treatments were named as OFYo (control), OFY1 (probiotics), and OFY2 (3% okara + probiotics). Yogurt was subjected to physicochemical, antioxidant, microbiological, and sensory analysis. The addition of okara significantly affected nutritional and antioxidant attributes of yogurt (p < 0.05). The results indicated that adding 3% okara affected the protein, fat, water holding capacity, and color. Total phenolic contents, DPPH (2,2-diphenyl-1-picrylhydrazyl) activity and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) activity increased due to the addition of okara. Likewise, the highest total viable count (8.25 log CFU/mL) and probiotic count (8.98 log CFU/mL) were noted in yogurt with 3% okara. Okara has dietary fibers; this dietary fiber acts as a prebiotic source for probiotic L. Rhamnosus. This shows that okara has a different prebiotic potential. The addition of okara has promising potential for the development of functional food.

Soybean Processing Wastes: Novel Insights on Their Production, Extraction of Isoflavones, and Their Therapeutic Properties

Soybean processing waste (SPW) has potential as a sustainable source of phytochemicals and functional foods. A variety of phytochemicals, nutrients, and minerals have been characterized from SPW using various analytical methods. SPW utilization strategies may provide a new way to increase production of bioactive compounds, nutritional supplements, and cosmetic ingredients. SPW has the potential for value-added processing, to improve commercial use, and to lower environmental pollution through proper use. Okara, a byproduct generated during soybean processing of tofu and soy milk, is rich in dietary fiber, isoflavones, and saponins. Isoflavones, an important class of biologically active compounds owing to their multifunctional and therapeutic effects, are extracted from SPW. Further, studies have shown that okara has potential prebiotic and therapeutic value in lowering the risk of noncommunicable diseases. Therefore, in this review, we focus on several extraction methods and pharmacotherapeutic effects of different SPWs. Their effective uses in functional foods, nutraceuticals, and health applications, as biocatalysts, and as value-added resources have been discussed.

Soybean processing wastes and their potential in the generation of high value added products

Soybean and its derivatives are rich sources of nutrients and bioactive compounds with antioxidant properties, however, the wastes with high nutritional value are discarded by the industry. This study aimed to evaluate centesimal composition, microbial safety and antioxidant activity of soybean processing wastes (okara and okara flour) and soymilk. High fiber, carbohydrate, energy and lipids contents were found. Antioxidant activity by spectrophotometric and Electron Paramagnetic Resonance assays showed values for soybean (72.4% and 83.5%), okara (9.6% and 7.7%), okara flour (30.7% and 11.5%) and soymilk (28.4% and 36.5%). The total phenolic content was an average of 3.33 mg of gallic acid equivalent.g-1. Infrared spectra revealed no significant changes in the absorption bands, guaranteeing non-alteration in the compounds composition after processing. Microbiological assays indicated that soybean derivatives are safe for consumption. These results reinforce that these wastes contain bioactive compounds of interest with great potential to generate high value added products.

Filling the Protein Gap in Ghana: The Role of Soy

The study assessed the nutrient value and desirability of eight improved soybean varieties, for use in soymilk, tofu and as an ingredient to enhance staple foods. The soymilk, tofu, and soybean residue (okara) yields were determined across all varieties. The okara was subsequently used in composite with cassava, as a recipe refinement of gari, a popular cassava-based ready-to-eat food. Multiple composite ratios were compared against a control of 100% cassava gari; 80% cassava: 20% okara, 70% cassava: 30% okara, and 50% cassava: 50% okara. The soymilk and tofu from the various varieties and okara enriched-gari were also evaluated for proximate and sensory qualities (n = 50) using standard protocols. No differences (p &gt; 0.05) existed among soybean varieties in terms of soymilk (p = 0.55; 13.0–14.1 L), tofu (p = 0.05; 0.12–0.15 kg/L) or okara (p = 0.08; 3.17–3.97 kg) yields. The proximate parameters evaluated for soymilk did not vary significantly (p &gt; 0.05) among varieties. However, for total solids (3.33–7.93°Brix; p &lt; 0.01) there were significant differences. Generally, there was an increasing trend in the crude protein, moisture, crude fat and total ash contents for the okara-enriched gari as the okara inclusion increased from 20 to 50%. Thus, the crude protein content of the 50% okara-enriched gari, the formulation with the highest okara incorporation was almost 11-times higher than the 100% cassava gari. The swelling capacity of the okara-enriched gari ranged from 3.29–5.47 and for water holding capacity 439.7–482.1%. The okara-enriched gari was equally preferred by consumers, except for colour which consumers were mostly indifferent towards. The 50%-okara enriched gari composite was compared equally with 100% cassava gari control. The sensory data showed that the “Favour” soybean variety was desirable for soymilk production while Salintuya 1 was desirable for tofu production. Recipe refinements using the desired varieties and compositing okara with cassava may help fill the protein gap among the vulnerable group in Ghana by improving the protein quality of ready-to-eat foods such as gari.

Anaerobic co-digestion of textile dyeing sludge: Digestion efficiency and heavy metal stability

Anaerobic co-digestion (AcoD) has become an important mean for the stabilization and recycling of textile dyeing sludge (TDS). Using the soybean okara byproduct (SOB) as a co-digestion substrate, the effects on AcoD performance and heavy metal stability were studied. The results indicated that the optimal mixing ratio was 1:1 (calculated by total sloid). Under this condition, the SCOD removal efficiency was 64% (that of TDS alone and SOB alone were 47% and 48%, respectively) and the cumulative methane production field was 503 L CH₄/kg VS (that of TDS alone and SOB alone were 435 L CH₄/kg VS and 408 L CH₄/kg VS, respectively). At the same time, the addition of SOB could also enhance the stability of heavy metals (Zn, Cu, Cr and Ni) in TDS. Remarkably, that could increase the steady state content nickel from 47.98% to 57.21%, while anaerobic digestion of TDS caused no increase but a decrease (only 42.13%). According to the risk assessment code analyses, the AcoD of TDS by SOB can significantly reduce the ecotoxicity risk caused by Ni, Zn and Cr.

Feeding okara, a soybean by-product, to dairy cows as partial protein source enhances economic indexes and preserves milk quality, intake, and digestibility of nutrients

This study was carried out to evaluate the potential of dietary inclusion of okara (a soybean by-product) on feed intake, apparent in vitro digestibility of dry matter, production and milk quality of dairy cows, and economic indexes. Four lactating Holstein cows were assigned to a 4 × 4 Latin square design. Treatments were control diet with no okara, diet with 35 g/kg okara, diet with 65 g/kg okara, and diet with 95 g/kg okara in dry matter basis. There was no effect of the inclusion of okara in the diet on the intake of dry matter, crude protein, and ether extract. The inclusion of okara did not affect the in vitro digestibility of nutrients either. However, neutral detergent fiber intake differed between levels 0 and 35 g/kg of okara in the diet, with lower (8.15 kg/day) and higher (9.30 kg/day) values for these treatments, respectively, with values intermediates for the other treatments. There was no significant difference for milk production, fat, protein, lactose, milk urea, somatic cell score, and conjugated diene. However, there was an effect of including okara on thiobarbituric acid reactive substance content in milk. Regarding the economic analysis, the inclusion of 95 g/kg of okara in the diet (dry matter) showed the best results for average feed cost, gross margin, breakeven, and profitability index. Okara can be included in diets of lactating dairy cows up to 95 g/kg of total mixed ration on dry matter basis without interfering on milk production, milk solids, nutrient digestibility, and providing beneficial economic indexes, being economically feasible.

Preparation and Characterization of Pickering Emulsions with Modified Okara Insoluble Dietary Fiber

Modified okara insoluble dietary fiber (OIDF) has attracted great interest as a promising Pickering emulsifier. At present, the modification methods are mainly physicochemical methods, and the research on microbial modified OIDF as stabilizer is not clear. In this work, modified OIDF was prepared by yeast Kluyveromyces marxianus fermentation. The potential of modified OIDF as a Pickering emulsifier and the formation and stability of OIDF-Pickering emulsions stabilized by modified OIDF were characterized, respectively. The results showed that the specific surface area, hydrophilicity, and electronegativity of the modified OIDF were all enhanced compared with the unmodified OIDF. The existence of the network structure between droplets is the key to maintain the stability of the emulsions, as indicated by Croy-Scanning Electron Microscope (Croy-SEM) and rheological properties measurements. The stability of OIDF-Pickering emulsions was evaluated in terms of storage time, centrifugal force, pH value, and ionic strength (NaCl). Moreover, the OIDF-Pickering emulsions stabilized by modified OIDF showed better stability. These results will contribute to the development of efficient OIDF-based emulsifiers, expand the application of emulsions in more fields, and will greatly improve the high-value utilization of okara by-products.

Enzymatic Metabolism of Flavonoids by Gut Microbiota and Its Impact on Gastrointestinal Cancer

Gastrointestinal (GI) cancer is a prevalent global health disease with a massive burden on health care providers. Internal and external factors such as obesity, smoking, diet (red meat), low socioeconomic status and infection with Helicobacter pylori are the critical risk factors of GI cancers. Flavonoids are natural phenolic compounds found abundantly in fruits and vegetables. Upon ingestion, 90% of flavonoids consumed require further enzymatic metabolism by the gut microbiome to enhance their bioavailability and absorption. Several epidemiological studies reported that consumption of flavonoids and their enzymatic conversion by gut microbes is strongly associated with the reduced risk of GI cancer development. This review summarizes the current knowledge on the enzymatic conversion of flavonoids by the human gut microbiome. It also addresses the underlying anti-GI cancer effects on metabolic pathways such as apoptosis and cellular proliferation. Overall, metabolites produced from flavonoid's enzymatic conversion illustrate anti-GI cancer effects, but the mechanisms of action need further clarification.

Prebiotic Impacts of Soybean Residue (Okara) on Eubiosis/Dysbiosis Condition of the Gut and the Possible Effects on Liver and Kidney Functions

Okara is a white-yellow fibrous residue consisting of the insoluble fraction of the soybean seeds remaining after extraction of the aqueous fraction during the production of tofu and soymilk, and is generally considered a waste product. It is packed with a significant number of proteins, isoflavones, soluble and insoluble fibers, soyasaponins, and other mineral elements, which are all attributed with health merits. With the increasing production of soy beverages, huge quantities of this by-product are produced annually, which poses significant disposal problems and financial issues for producers. Extensive studies have been done on the biological activities, nutritional values, and chemical composition of okara as well as its potential utilization. Owing to its peculiar rich fiber composition and low cost of production, okara might be potentially useful in the food industry as a functional ingredient or good raw material and could be used as a dietary supplement to prevent varied ailments such as prevention of diabetes, hyperlipidemia, obesity, as well as to stimulate the growth of intestinal microbes and production of microbe-derived metabolites (xenometabolites), since gut dysbiosis (imbalanced microbiota) has been implicated in the progression of several complex diseases. This review seeks to compile scientific research on the bioactive compounds in soybean residue (okara) and discuss the possible prebiotic impact of this fiber-rich residue as a functional diet on eubiosis/dysbiosis condition of the gut, as well as the consequential influence on liver and kidney functions, to facilitate a detailed knowledge base for further exploration, implementation, and development.

A review of okara (soybean curd residue) utilization as animal feed: Nutritive value and animal performance aspects

Year by year, huge quantities of by-products are generated during the manufacturing process of soybean-based products. Okara is one of the by-products, and it is an insoluble portion of the soybean. It consists of high moisture (8.4-22.9%); on dry matter basis, it contains high metabolizable energy (9.0-14.2 MJ/kg) and other components that include crude protein (20.9-39.1%), crude fiber (12.2-61.3%), crude fat (4.9-21.5%), and ash (3.4-5.3%). Fermentation of okara improves its nutritional quality and reduces its anti-nutrient contents. Due to animals' palatability, okara can be used to replace the soybean meal/concentrate feed partially or completely in ruminant's diet and partially in nonruminant's diet. Okara feeding does not depress the intake, digestibility, growth, milk production, blood metabolic profiles, and meat quality of animals. However, this by-product decays quickly due to its high moisture content, and its heavy weight and sticky nature make it difficult to process and expensive to dry using conventional methods. This paper thoroughly summarizes the utilization of okara as animal feed in the cause of developing a general guideline with favorable levels of inclusion in the diets of animals for its exploitation and valorization. This review will encourage further research to develop eco-friendly and value added feed for animals.

Chemical Modification of Biomass Okara Using Poly(acrylic acid) through Free Radical Graft Polymerization

Okara (Ok) or soybean residue is produced as a byproduct from the soybean milk and soybean curd industries world wide, most of which is disposed or burned as waste. It is important to explore the possibilities to convert okara to useful materials, because okara is a naturally renewable bioresource. Here, we report the chemical modification of okara by grafting poly(acrylic acid) (PAA) onto the backbones of okara in water medium and the characterization of the Ok-PAA graft copolymers. It was found that the received okara mainly contained insoluble contents in water. The insoluble okara component Ok(Ins) was suspended in water and activated with ammonium persulfate as an initiator, followed by grafting PAA through a free radical polymerization. After the graft polymerization, the product (Ok-PAA) was separated into precipitate and supernatant, which were dried to give Ok-PAA(pre) and Ok-PAA(sup), respectively. It was found that PAA was grafted on Ok backbones and co-precipitated with the insoluble Ok. In addition, Ok-PAA(sup) was found to be translucent as a result of the grafting of PAA. Further, the successful grafting of PAA onto okara backbones was proven by Fourier transform infrared, thermogravimetric analysis, and microscopic measurements. Ok-PAA(sup) dispersed in water formed nanoparticles with an average diameter of 420 nm, while Ok-PAA(pre) was clustered coarse particles in water. The rheological data including the storage modulus, loss modulus, and viscosity indicated that the Ok-PAA product was a viscoelastic gel-like material with potential for agricultural and environmental applications.

Valorisation of By-Products from Soybean (Glycine max (L.) Merr.) Processing

In recent years, increased awareness of the health benefits associated with consuming soy-based foods, knowledge of milk-related allergies and a move towards more sustainable food production have led to an increase in the number of available soy-based products. The biggest producers in the world, the USA, South America and China, are from the Pacific region. This enormous production is accompanied by the accumulation of related by-products, in particular, a substance that is known as okara. Okara is a paste that is rich in fibre (50%), protein (25%), fat (10%), vitamins and trace elements. Its proper use would lead to economic advantages and a reduction in the potential for polluting the environment. Its high fibre content and low production costs mean that it could also be used as a dietary supplement to prevent diabetes, obesity and hyperlipidaemia. Chemical or enzymatic treatment, fermentation, extrusion, high pressure and micronisation can all increase the soluble fibre content, and thus improve nutritional quality and processing properties. However, the product also degrades rapidly due to its high moisture content (70-80%), which makes it difficult to handle and expensive to dry by conventional means. The aim of this paper is therefore to thoroughly study the existing literature on this subject in order to develop a general protocol for okara exploitation and valorisation. A cost/benefit analysis could drive the design of eco-friendly, sustainable protocols for the preparation of high-value nutritional products.

Okara flour: its physicochemical, microscopical and functional properties

Purpose

Okara, which is the residue of hydrosoluble extract from soybean obtained after soymilk and tofu production, has high nutritional value and can be used for ingredient in specific food products. This study aims to evaluate the production and properties (physicochemical, microscopical and functional ones) of okara flour (OF) obtained from okara as a by-product of soymilk and tofu production.

Design/methodology/approach

Wet okara resulted from the soymilk process underwent convective drying up to reach mass stability (60°C for 12 h). OF properties were analyzed by official methods by AOAC, i.e. mineral composition was evaluated by atomic absorption equipment; color; water absorption index (WAI); milk absorption index (MAI); oil absorption capacity (OAC); and foam capacity (FC) required mixtures with water, milk and oil, separation and gravimetry, respectively; and microstructure was determined by a scanning electron microscope.

Findings

Results showed the potential OF has as a source of protein (24.74 g/100 g) and dietary fiber (58.27 g/100 g). Regarding its color after the drying process, OF was markedly yellow (b* parameter 20.16). Its WAI was 3.62 g/g, MAI was 4.33 g/g, OAC was 3.68 g/g and FC was 1.32 per cent. The microscopic analysis of OF showed that both loose and agglomerated particles had irregular structures and indefinite forms.

Originality/value

Production of flour from wet okara can be an alternative use of this by-product. This study showed important characteristics of OF and its possible application to the food industry. Thus, OF was shown as a potential ingredient with high nutritional value.

Mesophilic and thermophilic anaerobic digestion of soybean curd residue for methane production: Characterizing bacterial and methanogen communities and their correlations with organic loading rate and operating temperature

To find the optimal operation parameters and provide an explanation of methanogenic pathway for methane production in mesophilic (35 °C) and thermophilic (55 °C) anaerobic digestion (MAD, TAD) of soybean curd residue (SCR), MAD and MAD were contrastively investigated for 95 days. The maximum available OLR was identified as 3.3 gVS/L for both MAD and TAD. Compared to MAD, TAD exhibited a 20% higher average methane yield (0.591 L/gVS) and a 7.5% higher volatile solids removal efficiency (74.1 ± 10.4%). Bacterial phyla Bacteroidetes, Firmicutes and Proteobacteria dominated in MAD digesters while genus Defluviitoga was selectively enriched in TAD digesters due to higher temperature and organic loading pressure. Principal coordinates analysis of methanogen community showed that both temperature and OLR were crucial environmental variables shifting the taxonomic patterns of the methanogens. The enriched methanogen genus Methanothermobacter (93%) with a hydrogenotrophic methanogenic pathway had a close correlation with the TAD performance.

Biological Effect of Soy Isoflavones in the Prevention of Civilization Diseases

Scientific advancements in recent years have shed new light on the relationship between diet and human health. Nutrients play an important role in the prevention of many civilization diseases, such as osteoporosis, type II diabetes, hypercholesterolemia, and cardiovascular diseases. The biological activity of natural plant components allows their use in the treatment of various diseases, especially civilization diseases, to be speculated. Special attention is paid to phenolic compounds that have numerous health-promoting properties. Isoflavones, phenolic compounds, are commonly found in legumes, especially in soybeans. Their structural similarity to 17-β-estradiol (E2), the main female sex hormone, allows them to induce estrogenic and antiestrogenic effects by binding to estrogen receptors, and their consumption has been associated with a decreased risk of hormone-related cancers. In addition, numerous epidemiological studies and related meta-analyses suggest that soy consumption may be associated with a lower incidence of certain diseases. However, there are some doubts about the potential effects on health, such as the effectiveness of cardiovascular risk reduction or breast cancer-promoting properties. The purpose of this review is to present the current knowledge on the potential effects of soy isoflavone consumption with regard to civilization diseases.

Influence of Homogenization Time and Speed on Rheological and Volatile Composition in Olive-Based Pâtés

The influence of the homogenization time and speed on rheological and volatile composition in olive-based pâtés was studied. Five experimental trials were performed applying different combinations of time and speed homogenization: 1, 3, and 5 min at 12,000 rpm and 4000, 8000, and 12,000 rpm at 5 min. The obtained results showed that the processing parameters of the homogenization step significantly influenced the rheological and sensory properties of olive-based pâtés. Both time and speed influenced the rheological properties of the product. The increase of homogenization time and speed determined a significant reduction of hardness and syneresis. As regards color indices, significantly higher L* values were obtained when intermediate time and speed conditions were applied, whereas a* and b* indices showed a not univocal behavior. Both time and speed variables also influenced the volatile fraction of the pâtés (higher homogenization speed and time corresponded to higher terpenes and aldehydes).