Okara Protein Research Articles

Cavendish banana and red dragon fruit instant powdered with the addition of okara protein hydrolysate using foam mat drying

Cavendish banana and red dragon fruit instant powdered with the addition of okara protein hydrolysate using foam mat drying

Evaluation of Antioxidant Activities from a Sustainable Source of Okara Protein Hydrolysate Using Enzymatic Reaction

Okara is a solid byproduct created during the processing of soy milk. The production of protein hydrolysates utilizing enzymatic tests such as papain can result in the production of bioactive peptides (BPs), which are amino acid sequences that can also be produced from the okara protein by hydrolysis. The objective of this study was to investigate the antioxidant activities of okara hydrolysates using papain, based on the in silico and in vitro assays using the papain enzyme. We found that using the in silico assessment, the antioxidant peptides can be found from the precursor (glycinin and conglycinin) in okara. When used as a protease, papain provides the maximum degree of hydrolysis for antioxidative peptides. The highest-peptide-rank peptide sequence was predicted using peptide ranks such as proline–histidine–phenylalanine (PHF), alanine–aspartic acid–phenylalanine (ADF), tyrosine–tyrosine–leucine (YYL), proline–histidine–histidine (PHH), isoleucine–arginine (IR), and serine–valine–leucine (SVL). Molecular docking studies revealed that all peptides generated from the parent protein impeded substrate access to the active site of xanthine oxidase (XO). They have antioxidative properties and are employed in the in silico approach to the XO enzyme. We also use papain to evaluate the antioxidant activity by using in vitro tests for protein hydrolysate following proteolysis. The antioxidant properties of okara protein hydrolysates have been shown in vitro, utilizing DPPH and FRAP experiments. This study suggests that okara hydrolysates generated by papain can be employed as natural antioxidants in food and for further applications, such as active ingredients for antioxidants in packaging.

Preparation and quality of okara protein gel gummies

Okara protein (OP) was extracted by alkali solution and acid-isolation method using bean dregs as raw materials. With OP as the main raw material, the mixed gelatin and modified starch as the gelling agent, xylitol as the sweetener, and buffered lactic acid as the sour agent, the elasticity, hardness, stickiness and chewiness of the texture analyzer were analyzed by the single-factor test and orthogonal test. Combined with sensory evaluation, the optimal formula for the preparation of OP gel gummies was comprehensively obtained as: the ratio of gelatin to modified starch was 9:1; the xylitol addition was 18 g; the addition of buffered lactic acid was 0.7mL, and the addition of OP solution was 16mL, respectively. The gel gummies prepared under this formula have the advantages of suitable sweetness and sourness, good taste, good stickiness and uniform color. It also has special physiological functions, such as immune regulation and antihypertensiveness.

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 (2.8g/l at 3 %w/v protein concentration) due to the improved protein solubility in the culture medium (89 %) and smaller particle size (0.2μm) 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.

Antioxidant Activity and Amino Acid Composition of Okara Protein Hydrolysate

Okara (tofu dregs) is a soybean waste product from the tofu and soymilk processing industry. To create a useful product, the remaining protein content in okara must be used. The goal of this study was to determine the enzyme-substrate (E/S) ratio capable of producing the highest antioxidant activity from okara protein hydrolysate, as well as the amino acid composition of such a protein hydrolysate (especially the amino acid potential as antioxidants). To produce protein concentrate, the protein of okara was isolated using an alkaline extraction method followed by isoelectric precipitation. The protein concentrate was then hydrolyzed for six hours with papain enzyme at 50-55 °C and pH 7, with E/S ratios of 3%, 4%, 5%, 6%, and 7%. Using the DPPH method, the antioxidant activity of the obtained okara protein hydrolysate was determined. The HPLC method was used to determine the amino acid composition of the protein hydrolysate. The E/S ratio of 4% had the highest antioxidant activity (98.86%); the composition of amino acids L-Phenylalanine, L-Isoleucine, L-Valine, L-Glycine, L-Lysine, L-Tyrosine, L-Proline, L-Histidine, L-Cysteine and L-Methionine potentially contributed to the antioxidant activity effect. These findings suggest that okara protein hydrolysate has the potential to be used as an antioxidant-rich food ingredient.
 Keywords: antioxidant, okara, protein hydrolysate, amino acid

Effects of electron beam irradiation pretreatment on the structural and functional properties of okara protein

The structural and functional properties of okara protein pretreated with electron beam irradiation (EBI) at different doses (0–10 kGy) were investigated. The results of Fourier transform infrared spectroscopy spectra and fluorescence spectra indicated that EBI treatment decreased the α-helix and β-sheet proportion, contributing to a less compact tertiary conformation, thereby increased the fluorescence intensity with a red shift of λmax. Scanning electron microscopy images indicated that okara protein was fragmented into smaller pieces and the surface was uneven with pores after EBI treatment. The solubility, thermal stability and emulsification characteristics of okara protein were regulated by modifying its structure by EBI treatment. When the EBI treatment dose was 6 kGy, the protein had the highest solubility, as well as emulsification characteristics. Taken collectively, these results demonstrate that EBI can improve the functional properties of okara protein, which may widen the application of the protein.

Anti-fatigue effects of enzyme-hydrolyzed okara in C2C12 myotubes and Sprague-Dawley rats.

Okara is a by-product of tofu or soymilk production processes. The disposal of huge quantities of okara is a significant issue. Based on previous reports, protein hydrolysis can release excess free amino acids and small peptides from okara and exhibit anti-fatigue function. We aimed to investigate the anti-fatigue effect of okara protein hydrolysate (OPH) in vitro and in vivo. In the first phase, we treated C2C12 myotubes with different processed OPHs to detect mitochondrial functions. The results revealed that OPH hydrolyzed with alcalase containing 2% E/S for 2 h increased the mitochondrial mRNA level (cytochrome b and cytochrome c oxidase I) and enzyme activity (citrate synthase and cytochrome c oxidase) most efficiently. In the second phase, we conducted animal studies to assess the anti-fatigue function of OPH. After acclimatization, 8 week-old male Sprague-Dawley (SD) rats were randomly classified into four groups: (1) control group, (2) 1X-OPH, (3) 2X-OPH, and (4) 5X-OPH (8 rats per group, treated for 28 days). The results indicated that the intake of OPH for 28 days increased the exhaustive swimming time of rats and lowered the increment of the lactate ratio, as well as the activity of lactate dehydrogenase and creatine kinase. These results indicated that OPH improves exercise performance and anti-fatigue function in male SD rats. Therefore, OPH could be a potential health supplement for anti-fatigue function.

Effect of cavitation jets on the physicochemical properties and structural characteristics of the okara protein.

The structural andphysicochemical properties of okara protein (OP) subjected to different cavitation jet (CJ) treatment times (0-15min) were analyzed. In this study, the microstructure and apparent morphology of OP were analyzed by Raman spectrum, fluorescence spectrum, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and atomic force microscopy (AFM). Physicochemical properties, such as emulsion ability (EA), emulsion stability index (ESI), foaming characteristics (FC), foaming stability (FS), and solubility analysis of the OPs, were characterized. Raman spectrum analysis showed that CJ treatment caused increases in the ordered structure of OPs (α-helix, β-sheet, and β-turn), and the disulfide bond g-g-g and g-g-t modes, while it caused a decrease in the t-g-t mode. However, the tertiary structure of OP unfolded and mostly degraded into small subunits because of higher cavitation, shear and temperature effects. AFM observation indicated that CJ resulted in a more uniform distribution of OP. Moreover, changes in the structure of OP significantly affected its functional properties. The results showed that when CJ treatment time was 10min, the solubility of OP was up to (28.72 ± 1.26)%, the soluble protein content of okara was up to (10.44 ± 0.03)g/100g,and interface properties were better. In summary, OP has great potential for application in the food area, especially in emulsifying agent and foam system. PRACTICAL APPLICATION: The cavitation jet technology improves the structure and physical and chemical properties of the protein extracted from soybean residue (okara) and provides new ideas for the further development and utilization of soybean residue protein, which may lead to the production of high-value-added functional ingredients from the processing of soybean byproducts.

Microencapsulation of okara protein hydrolysate by spray drying: physicochemical and nutritive properties, sorption isotherm, and glass transition temperature

The objective of this work was to evaluate the physicochemical and nutritive properties, sorption isotherm, and glass transition temperature (Tg) of okara protein hydrolysate microencapsulated with maltodextrin or modified starch by spray drying. Freeze-dried hydrolysate without a wall material was obtained as a non-encapsulated sample. The type of wall material had no significant influence on the powder properties. There were differences between encapsulated and non-encapsulated samples, mainly in the sugar profile, mean particle size (∼13 and 208 µm, respectively), and anhydrous powder Tg (∼100 and 55 °C, respectively). Microencapsulation improved the critical relative humidity of storage from 25% to ∼55%.

Enhanced acidic stability of O/W emulsions by synergistic interactions between okara protein and carboxymethyl cellulose

The application of okara protein (OP) in emulsions is yet to be fully explored. The present work aims to investigate the effects of carboxymethyl cellulose (CMC) - OP complexes on the emulsion properties and emulsion stability. CMC (0–5 g/kg) was introduced to electrostatically interact with the OP (10 g/kg) at pH 4.0, and then O/W emulsions (1:9, g/g) were prepared by the complexes and systematically characterized. As the CMC concentration increased from 0 to 5 g/kg, the particle size of the OP-CMC complexes decreased from 6400 to 380 nm, while the ζ-potential decreased from 1 to −28 mV. As for the emulsions, their ζ-potential was reduced from −1 to −28 mV while their droplet size decreased from 201 to 10 μm with less flocculation. The surface protein content decreased from 97% to 73% while less creaming was observed in the fresh emulsions. The results obtained in the present work demonstrated that the negatively charged OP-CMC complexes pre-formed by electrostatic interaction contributed to an improved O/W emulsion stability at pH 4.0. The results obtained may be conducive to the potential utilization of OP-based dairy products, especially in an acid environment.

Assessment of the Physicochemical and Conformational Changes of Ultrasound-Driven Proteins Extracted from Soybean Okara Byproduct.

This study was aimed at the valorization of the okara byproduct deriving form soy food manufacturing, by using ultrasound at different temperatures for extracting the residual proteins. The physicochemical and conformational changes of the extracted proteins were investigated in order to optimize the procedure. Increasing the temperature from 20 up to 80 °C greatly enhanced the yields and the protein solubility without affecting the viscosity. The protein secondary and tertiary structures were also gradually modified in a significant way. After the ultrasonication at the highest temperature, a significant morphological transition from well-defined single round structures to highly aggregated ones was observed, which was confirmed by measuring the water contact angles and wettability. After the ultrasound process, the improvement of peptides generation and the different amino acid exposition within the protein led to an increase of the antioxidant properties. The integrated strategy applied in this study allows to foster the okara protein obtained after ultrasound extraction as valuable materials for new applications.

Processed by-Products from Soy Beverage (Okara) as Sustainable Ingredients for Nile Tilapia (O. Niloticus) Juveniles: Effects on Nutrient Utilization and Muscle Quality.

Simple SummaryThe consumption of soy products increases worldwide and generates large amounts of by-products, which are often discarded. Okara is a soybean by-product with high nutritional value. This work evidenced the great potential of okara meal, after appropriate technological processing, to be used as feed ingredient in Nile tilapia diets. It was clearly demonstrated the effectiveness of the autoclave and the use of proteases from C. cardunculus without fermentation to increase okara nutrient bioavailability. The inclusion of up to 20% okara meal in diets for tilapia did not affect growth performance, nutrient utilization, or whole body composition compared to a reference diet. Flesh quality remained largely unaffected, although fish fed with AOK diets had the highest density of muscle fibers.The apparent digestibility coefficients (ADCs) of differently processed okara meals were assessed in Nile tilapia diets: dried okara not autoclaved (FOK), dried okara autoclaved (AOK), okara hydrolyzed with Alcalase (ALOK) or Cynara cardunculus proteases (CYOK), and hydrolyzed okara fermented with lactic bacteria: Lactobacillus rhamnosus R11 (CYR11OK) or Bifidobacterium animalis ssp. lactis Bb12 (CYB12OK). Okara processing significantly affected nutrient digestibility: dry matter ADC was highest in CYR11OK (80%) and lowest in FOK (40%). The lowest protein digestibility was observed in CYR11OK (72%), and the highest in AOK (97%) and CYOK (91%), evidencing the effectiveness of the autoclave and the use of C. cardunculus proteases to increase okara protein bioavailability. The inclusion of up to 20% of AOK or CYOK did not affect fish growth, nutrient utilization, or whole body composition of Nile tilapia. The flesh quality (color, pH, water activity, cohesiveness, elasticity and resilience) was not affected by the dietary incorporation of AOK or CYOK. Fish fed with AOK diets stand out for their high density of muscle fibers, particularly in AOK20, which can explain their high muscle firmness and may result in further hypertrophic growth. Altogether, results suggest that hydrolyzed or autoclaved okara are valuable ingredients for Nile tilapia diets.

Carboxymethyl cellulose/okara protein influencing microstructure, rheological properties and stability of O/W emulsions.

The role of protein-polysaccharide interactions and their mixtures has been a vital factor affecting the formation and stability of food emulsions. Okara protein (OP), which is extracted from the by-product of soybean processing, has received much attention because of its abundant sources and potential attributes with respect to food formulation. Carboxymethyl cellulose (CMC), a well-known food-grade polysaccharide additive, has been widely utilized in the protein-polysaccharide system, whereas, among the proteins, the role of OP has not yet been explored. The present study first assessed the ζ-potential and hydrodynamic diameter of aqueous mixtures containing OP (1.0wt%) and CMC (0-0.5wt%), followed by the investigation of OP-CMC mixtures stabilized O/W emulsions. As CMC increased, oil droplet size, surface protein adsorption, apparent viscosity and storage modulus increased, whereas the loss tangent decreased. CMC resulted in emulsion destabilization compared to emulsions without CMC, whereas a higher concentration of CMC promoted emulsion stability against creaming for emulsions in the presence of CMC. The results provide information with respect to OP and CMC being incorporated into food formulations and also strengthen our understanding of the related mechanism, in addition to facilitating the further utilization of OP. © 2020 Society of Chemical Industry.

Effect of pH on okara protein-carboxymethyl cellulose interactions in aqueous solution and at oil-water interface

The physicochemical and interfacial properties of Okara protein (OP) are susceptible to be affected by various factors. In this respect, the role of inter- and intramolecular interactions between OP and carboxymethyl cellulose (CMC) were explored by in situ experiments. OP/CMC aqueous mixtures, containing 1.0 wt% OP and 0–0.5 wt% CMC, were prepared at pH 7.0 and 4.0. Subsequently, their physicochemical properties, interactions, and interfacial adsorption were comparatively characterized. OP formed larger aggregates at lower pH as confirmed by the visual appearance. The addition of CMC reduced the surface hydrophobicity and increased viscosity of OP/CMC mixtures regardless of pH. CMC increased the hydrodynamic diameter of mixtures at pH 7.0, while it led to more negatively-charged complexes with decreasing size at pH 4.0. Noticeably, the results regarding the interfacial pressure, adsorption kinetics and interfacial dilatational viscoelastic properties presented three remarkable phenomena: Low concentrations of CMC hardly affected the initial interfacial performance of OP at pH 7.0, whereas the latter was greatly reduced at high CMC concentrations. Moreover, high CMC concentrations appropriately reinforced the interfacial performance of OP at pH 4.0.

Adjustment of the structural and functional properties of okara protein by acid precipitation

Acid precipitation has a great influence on the extraction and structural properties of plant proteins, especially for proteins in poorly soluble raw materials. The structural and functional properties of okara protein (OP) precipitated by different acids (HCl, citric acid, and malic acid) were investigated. HCl induced the lowest surface hydrophobicity (H0), while citric acid led to the lowest absolute value of ζ-potential and the largest size of OP. By contrast, the highest H0 and absolute value of ζ-potential, as well as the smallest size, were observed in OP precipitated by malic acid. Basic 7S globulin (Bg 7S) was detected in OP, especially for OP precipitated by malic acid and citric acid. Differences were also observed in the functional properties of OP. HCl contributed to the highest solubility, water holding capacity (WHC), foaming ability index (FAI), and foaming stability index (FSI). Citric acid induced the highest oil holding capacity (OHC) and emulsifying stability index (ESI). Malic acid resulted in the lowest FAI, FSI, and ESI. These results indicated that acid precipitation was able to alter functional properties of okara protein via affecting the structure, which made it be appliable in extracting protein from poorly soluble raw materials and widen the applications of obtained protein.

Enhanced antioxidant activity of okara through solid state fermentation of GRAS Fungi

Abstract The enhancement of antioxidant activity of fermented okara was investigated using fungal solid-state fermentation. The initial fungal concentration and water activity were found to influence the enhanced antioxidant capacity of fermented okara. Extracellular enzymes, especially proteases and carbohydrases might facilitate the hydrolysis of okara protein that yielded antioxidative amino acids and peptides, as well as the release of isoflavones-derived components. Fermentation of okara with R. oligosporus with 1.04×10-3 gDCW/gokara as initial concentration, water activity of 0.931 was found to yield the highest antioxidant strength. Whereas for A. Oryzae, 1.6×10-3 gDCW/gokara was optimum as the initial concentration with water activity of 0.913. With these optimum conditions, solid-state fermentation of okara could enhance the antioxidant activity up to 2.6- and 5.5-fold, respectively for R. oligosporus and A. oryzae. Besides having an enhanced antioxidant activity, the fermented okara also had higher protein content, amino nitrogen content, and protein digestibility.

Enzymatic hydrolysis of okara protein concentrate by mixture of endo and exopeptidase

The objective of this study was to obtain a model and optimize the enzymatic hydrolysis of okara protein concentrate using a combined mixture of alcalase and flavourzyme. The highest degree of hydrolysis (DH) was 22% obtained at 40°C, enzyme/substrate ratio of 5 g/100 g protein, pH of 7.1, and alcalase/flavourzyme ratio of 90%/10%. Additionally, under optimal condition, protein hydrolysates with DH 0, 6, 12, 18, and 22% were obtained and analyzed. Protein hydrolysis was confirmed by the electrophoretic profile, which showed diffuse bands with smaller molecular weight. The total amino acid profile showed that the protein hydrolysate with DH 22% had a balanced composition of all essential amino acids. All protein hydrolysates contained threefold higher aglycone isoflavone content than the okara protein concentrate. Enzymatic hydrolysis enhanced the antioxidant capacity of the protein hydrolysates, which was approximately 2.3- and 2.7-fold higher according to ABTS and FRAP analyses, respectively, compared to the intact protein. Thus, the protein hydrolysate can be incorporated into real food systems as a natural antioxidant alternative to the synthetic compounds. Practical applications Bioactive compounds have increasingly been studied due to their beneficial effects, such as antioxidant capacity. Therefore, it is necessary to research how to obtain these bioactive compounds and what are the most important parameters to obtain an efficient process. Most papers evaluated the hydrolysis process using only one enzyme. In this work, a central composite rotatable design was carried out to optimize the use of two enzymes with different specificities to obtain bioactive compounds with high antioxidant capacity.

Bioalcohol production from spent coffee grounds and okara waste biomass by engineered Bacillus subtilis

Protein biomass is one of the useful biomasses which could be converted to various biochemicals. In this study, protein-rich food wastes such as SCG (spent coffee ground) and okara waste were utilized for production of bioalcohol of ethanol, isobutanol, and methylbutanols by engineered Bacillus subtilisΔcodYΔbkdBΔrelA. Protein biomass is composed of amino acids, and some are depleted in the early phase of biotransformation process. This causes cellular stress and low growth rate of host B. subtilis strains leading to low productivity of biochemicals. To overcome this nutritional stress, B. subtilis host strain was engineered to restore nutritional stress by inactivation of RelA regulatory protein with additional supplement of lysine and cysteine. Finally, the engineered B. subtilis ΔcodYΔbkdBΔrelA showed the highest bioalcohol production of 0.59 ± 0.09 g/L and 0.43 ± 0.03 g/L from SCG and okara protein resources, respectively.

Effect of steam explosion on dietary fiber, polysaccharide, protein and physicochemical properties of okara

Okara is the byproduct of tofu and soymilk industries. A large amount of okara is produced annually in the world, but only a small amount is fully utilized. The effect of steam explosion (SE) treatment on dietary fiber, protein and physiochemical properties of okara was investigated in this paper. The results showed that untreated okara contained 76.38% total dietary fiber (TDF) and 18.10% protein, but the content of soluble dietary fiber (SDF) was only 1.34%. After SE treatment, SDF content increased significantly. When the SE strength was 1.5 MPa for 30s, SDF content increased to 36.28%, higher by 26 times compared to the control okara. However, the contents of TDF and SDF both decreased when the SE strength enhanced further. Gel filtration chromatography showed that molecular weight of okara polysaccharides were distributed from 55 KDa to 2087 KDa. With the increase of SE strength, the ratio of low molecular weight polysaccharides increased and the molecular weight range of polysaccharides became narrower. Okara protein showed two molecular weight peaks. After SE treatment, the area of high molecular weight peak decreased and low molecular weight peak increased. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that okara protein appeared in five bands: 73.7 KDa, 55 KDa, 41.1 KDa, 32.7 KDa and 20.2 KDa. After SE treatment, the bands of 73.7 KDa, 55 KDa and 41.1 KDa weakened markedly, indicating high SE strength can dissociate macromolecular protein aggregates. Water solubility of okara increased significantly, while swelling capacity, oil and water holding capacities decreased after SE treatment. Scanning electron microscopy (SEM) demonstrated that the loose sheet structure of okara surface was destroyed into small fragments after SE treatment and the internal nucleated structure was disintegrated into small particles at high SE strength. The change in morphological structure also produced important influences on physiochemical properties of okara. This study suggested that SE treatment is an effective method for improving SDF content and quality of okara, so as to expand its development and utilization.

Production of Hydrolysate of Okara Protein Concentrate with High Antioxidant Capacity and Aglycone Isoflavone Content

This work aimed to evaluate the enzymatic hydrolysis of okara protein concentrate with respect to degree of hydrolysis (DH) in order to obtain a protein hydrolysate with high antioxidant capacity and aglycones isoflavone content. A central composite rotatable design was carried out to evaluate the influence of temperature (40 to 70°C), enzyme:substrate ratio (0.5 to 5.0%, g/100g protein) and pH (7.0 to 9.0) on DH. The optimal condition was 55°C, pH 9 and enzyme:substrate ratio of 5.0%, resulting a DH value of 35.5%. After protein hydrolysis at optimal condition, the antioxidant capacities of hydrolysate increased from 58.29 to 383.49 μM Trolox equivalent/g solids (ABTS method) and 2.41 to 15.32 μM Trolox equivalent/g solids (FRAP method) when compared with protein concentrate. The higher radical scavenging ability of hydrolysate was due to great amount of hydrophobic amino acids (34.92 g/100g protein). Moreover, the protein hydrolysate obtained under optimal condition had 3 times higher aglycone isoflavone content than non-hydrolyzed sample. These results showed that protein hydrolysis of okara could be an alternative approach to increase antioxidant activity and enrich aglycones isoflavone in this byproduct generated from soymilk industry.