Insoluble dietary fibre from okara (soybean residue) modified by yeast Kluyveromyces marxianus

Advancements in modifying insoluble dietary fiber: Exploring the microstructure, physicochemical properties, biological activity, and applications in food industry-A review

Recent research has primarily focused on strategies for modifying insoluble dietary fiber (IDF) to enhance its performance and functionality. IDF is obtained from various inexpensive sources and can be manipulated to alter its biological effects, making it possible to revolutionize food processing and nutrition. In this review, multiple IDF modification techniques are thoroughly examined and discussed, with particular emphasis on the resulting changes in the physicochemical properties, biological activities, and microstructure of the fiber. An extensive overview of the practical applications of modified IDF in food processing is provided. Our study aims to raise awareness about the vast possibilities presented by modified IDF and encourage further exploration and utilization of this field in the realm of food production.

Effect of structural characteristics on the physicochemical properties and functional activities of dietary fiber: A review of structure-activity relationship

Dietary fibers come from a wide range of sources and have a variety of preparation methods (including extraction and modification). The different structural characteristics of dietary fibers caused by source, extraction and modification methods directly affect their physicochemical properties and functional activities. The relationship between structure and physicochemical properties and functional activities is an indispensable basic theory for realizing the directional transformation of dietary fibers' structure and accurately regulating their specific properties and activities. In this paper, since a brief overview about the structural characteristics of dietary fiber, the effect of structural characteristics on a variety of physicochemical properties (hydration, electrical, thermal, rheological, emulsifying property, and oil holding capacity, cation exchange capacity) and functional activities (hypoglycemic, hypolipidemic, antioxidant, prebiotic and harmful substances-adsorption activity) of dietary fiber explored by researchers in last five years are emphatically reviewed. Moreover, the future perspectives of structure-activity relationship are discussed. This review aims to provide theoretical foundation for the targeted regulation of properties and activities of dietary fiber, so as to improve the quality of their applied products and physiological efficiency, and then to realize high value utilization of dietary fiber resources.

Effect of insoluble dietary fiber on printing properties and molecular interactions of 3D-printed soy protein isolate-wheat gluten plant-based meats

Insoluble dietary fiber (IDF) has been characterized to prevent chronic diseases and improve gastrointestinal health, and it has been added to 3D printing plant-based meats (PM) to enhance texture and increase nutritional properties. Therefore, the aim of this study was to investigate the effects of IDF on 3D printing properties and molecular interactions of soy protein isolate (SPI) - wheat gluten (WG) PM. Without the participation of IDF, PM appeared to collapse. When the IDF concentration increased from 0 to 10 %, PM displayed good printing properties, water holding capacity, tensile strength, and elongation at break were increased. Tensile strength and elongation at break reached a maximum at 10 % IDF, and clearly similar results were found for texture attribute indices such as hardness, gumminess, chewiness, and cohesiveness after cooking. All printing inks exhibited shear-thinning behavior and solid-like viscoelasticity, but the structural recovery properties of 3D-printed PM deteriorated when the IDF content was over 10 %. Intermolecular forces indicated that the addition of IDF enhanced the disulfide bonds so that 10 % IDF presented better printing properties. These results indicated the potential for developing PM with dietary fiber functionality through 3D printing technology.

Identification of Cellulose-Degrading Bacteria and Assessment of Their Potential Value for the Production of Bioethanol from Coconut Oil Cake Waste

Bioconversion of lignocellulosic biomass is a highly promising alternative to rapidly reduce reliance on fossil fuels and greenhouse gas emissions. However, the use of lignocellulosic biomass is limited by the challenges of efficient degradation strategies. Given this need, Bacillus tropicus (B. tropicus) with cellulose degradation ability was isolated and screened from rotten dahlia. The strain efficiently utilized coconut oil cake (COC) to secrete 167.3 U/mL of cellulase activity. Electron microscopy results showed significant changes in the structure and properties of cellulose after treatment with B. tropicus, which increased the surface accessibility and the efficiency of the hydrolysis process. The functional group modification observed by Fourier transform infrared spectroscopy indicated the successful depolymerization of COC. The X-ray diffraction pattern showed that the crystallinity index increased from 44.8% to 48.2% due to the hydrolysis of the amorphous region in COC. The results of colorimetry also reveal an efficient hydrolysis process. A co-culture of B. tropicus and Saccharomyces cerevisiae was used to produce ethanol from COC waste, and the maximum ethanol yield was 4.2 g/L. The results of this work show that B. tropicus can be used to prepare biotechnology value-added products such as biofuels from lignocellulosic biomass, suggesting promising utility in biotechnology applications.

Effects of Alkaline Hydrogen Peroxide and Cellulase Modifications on the Physicochemical and Functional Properties of Forsythia suspensa Dietary Fiber

Besides active substances, Forsythia suspensa is rich in dietary fiber (DF), but it is often wasted or discarded and not put to good use. In order to improve the function of Forsythia DF, it was modified using alkaline hydrogen peroxide (AHP) and cellulase (EM). Compared to the control DF (ODF), the DF modified using AHP (AHDF) and EM (EMDF) had a looser microstructure, lower crystallinity, and higher oil holding capacity (OHC) and cation exchange capacity (CEC). The AHP treatment significantly increased the water holding capacity (WHC) and water swelling ability (WSA) of the DF, while the EM treatment achieved just the opposite. Moreover, the functional properties of AHDF and EMDF, including their cholesterol adsorption capacity (CAC), nitrite ion adsorption capacity (NAC), glucose adsorption capacity (GAC), glucose dialysis retardation index (GDRI), α-amylase inhibitory activity, and DPPH radical scavenging activity, were far better than those of ODF. Together, the results revealed that AHP and EM modifications could effectively improve or enhance the physicochemical and functional properties of Forsythia suspensa DF.

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.

Effects of cavitation-jet technology combined with enzyme treatment on the structure properties and functional properties of OKARA insoluble dietary fiber

In this study, a new composite modification method utilizing a cavitation jet combined with a composite enzyme (cellulase and xylanase) was developed to modify the insoluble dietary fibre (IDF) of okara (IDF was first treated with the cavitation jet at 0.3 MPa for 10 min, and then 6% of the enzyme was added, the composite enzyme with a 1:1 enzyme activity was hydrolysed for 1.5 h to obtain the modified IDF), and explored the structure-activity relationship between the structural properties, physicochemical properties and biological activities of IDF before and after modification. Under the action of cavitation jet and double enzyme hydrolysis, the modified IDF had a wrinkled and loose porous structure, which improved the thermal stability. Its water holding capacity (10.81 ± 0.17 g/g), oil holding capacity (4.83 ± 0.03 g/g) and swelling capacity (18.60 ± 0.60 mL/g) were significantly higher than those of unmodified IDF. In addition, compared with other IDFs, the combined modified IDF had greater advantages in nitrite adsorption (13.75 ± 0.14 μg/g), glucose adsorption (6.46 ± 0.28 mmol/g) and cholesterol adsorption (16.86 ± 0.83 mg/g), and improved in vitro probiotic activity and in vitro anti-digestion rate. The results show that the cavitation jet combined with compound enzyme modification method can effectively improve the economic value of okara.

Study on physicochemical, structural, and functional properties of Zhengdan958 and Xianyu335 cornstarch from newly harvested corn under postharvest ripening conditions at ambient temperature

The importance of starch in nutrition and industry is unquestionable. This study investigated the changes in physicochemical, structural, and functional properties of cornstarch from newly harvested Zhengdan958 (Zd958) and Xianyu335 (Xy335) corn during for 0, 20, 40, and 60 d at ambient temperature. The results showed no significant changes in the proximate components and apparent structure of Zd958 and Xy335 cornstarch under postharvest ripening conditions. Compared with 0 d, the molecular weight distribution and mass fraction of Zd958 and Xy335 cornstarch have changed significantly, the relative crystallinity (RC) has significantly increased from 26.4% to 26.5%-28.8% and 28.4%, and R1045/1022 has significantly increased from 0.828 to 0.826 to 0.843 and 0.883, respectively. The changes in structure indicated that the synthesis and rearrangement of cornstarch molecules formed highly ordered crystalline structures, and the ordered structures of long-range and short-range molecules increased. Moreover, the changes in structure affected the pasting characteristics and texture profiles of cornstarch, therefore, affecting the final food quality.

Optimization of Mixed Fermentation Conditions of Dietary Fiber from Soybean Residue and the Effect on Structure, Properties and Potential Biological Activity of Dietary Fiber from Soybean Residue

Soybean residue is a by-product of soybean product production that is wasted unreasonably at present. Accomplishing the efficient utilization of soybean residue can save resources. A composite microbial system was constructed using lactic acid bacteria (LAB) and Saccharomyces cerevisiae (SC), and modified soybean residue was prepared by solid fermentation. In order to explore the value of modified soybean residue as a food raw material, its physical and chemical properties, adsorption properties, and antioxidant properties were studied. The results showed that the soluble dietary fiber (SDF) yield of mixed fermentation (MF) increased significantly. Both groups of soybean residues had representative polysaccharide infrared absorption peaks, and MF showed a looser structure and lower crystallinity. In terms of the adsorption capacity index, MF also has a higher adsorption capacity for water molecules, oil molecules, and cholesterol molecules. In addition, the in vitro antioxidant capacity of MF was also significantly higher than that of unfermented soybean residue (UF). In conclusion, our study shows that mixed fermentation could increase SDF content and improve the functional properties of soybean residue. Modified soybean residue prepared by mixed fermentation is the ideal food raw material.

Effects of electron beam irradiation treatment on the structural and functional properties of okara insoluble dietary fiber

BACKGROUND

Insoluble dietary fiber (IDF) has beneficial physiological effects, such as the promoting of intestinal peristalsis, the improving of intestinal flora, and the absorbing of some harmful substances. Okara, a byproduct of soybean processing, is a potential source of IDF. But the larger particle size and poor water solubility of okara IDF have adverse effects on sensory properties and functional characteristics. Therefore, we used an emerging type of physical method is electron beam irradiation (EBI) to modify okara, and investigated that the effects of EBI doses on the structure and functional properties of okara IDF.

RESULTS

It was found that the electron beam treatment damaged the crystalline structure of IDF. Observation of the surface of EBI-treated IDF revealed a loose and porous morphology rather than the typical smooth structure. At a dose of 6 kGy, a smallest particle size and largest specific surface area of IDF was obtained, and these factors increased the apparent viscosity of an IDF dispersion. The water holding capacity, swelling capacity and the oil holding capacity upon irradiation at 6 kGy increased 74.13%, 84.76% and 41.62%, respectively. In addition, the capacity for adsorption of cholesterol, sodium cholate, glucose and nitrite ion were improved after electron beam treatment.

CONCLUSION

The modified okara IDF showed improved particle sizes and hydration properties, and these changes correlated with an improvement to the rough taste of IDF and improvements to the texture and storage period upon supplementation into food. © 2022 Society of Chemical Industry.

Screen of high efficiency cellulose degrading strains and effects on tea residues dietary fiber modification: Structural properties and adsorption capacities

In our study, two high efficiency cellulose degrading strains were screened, isolated and identified as Cochliobolus kusanoi and Aspergillus puulaauensis by 18S rDNA gene sequencing. In addition, the composite microbial system was constructed to develop the synergistic effect among different strains. Under the optimum conditions, the yield of soluble dietary fiber from tea residues by mixed fermentation method (MF-SDF) dramatically increased compared to single strain fermentation. The structural analysis demonstrated that all samples possessed the representative infrared absorption peaks of polysaccharides, whereas MF-SDF revealed more loose structure, lower crystallinity and smaller molecular size. For the adsorption capacities indexes, MF-SDF also owned the highest adsorbing capacity for the water molecule, oil molecule, cholesterol molecule and nitrite ion. Overall, our data showed that mixed fermentation method could be better choices to improve the functional properties of dietary fiber, and screening of cellulose degrading strains could provide new thinkings for the study of dietary fiber modification and realize high-quality utilization of crop residues.

Physicochemical structure and functional properties of soluble dietary fibers obtained by different modification methods from Mesona chinensis Benth. residue

Alkaline hydrogen peroxide (AHP), high-temperature cooking combined with ultrasonic (HTCU) and high-temperature cooking combined with complex enzyme hydrolysis (HTCE) were used to modify soluble dietary fiber (SDF) in Mesona chinensis Benth. residue (MCBR), then the structural and in vitro functional properties of A-SDF, HU-SDF and HE-SDF were investigated. Results showed that the three treatments significantly increased the yield of SDF. Scanning electron microscopy, FT-IR, monosaccharide composition, X-ray diffraction, molecular weight distribution and thermal stability analysis were employed to determine the structural changes. Compared with the control SDF (CK-SDF), HE-SDF and HU-SDF had looser and more porous microstructure, as well as lower crystallinity. In contrast to HE-SDF and HU-SDF, A-SDF exhibited a dense wavy microstructure, and elevated crystallinity and thermal stability. In addition, the monosaccharide composition and molecular weight of HU-SDF, HE-SDF and A-SDF were significantly altered as compared to CK-SDF. Moreover, the functional properties of HE-SDF and HU-SDF, including water holding capacity (WHC), oil holding capacity (OHC), glucose adsorption capacity (GAC), α-amylase activity inhibition ratio (α-AAIR), cholesterol adsorption capacity (CAC) and nitrite ion adsorption capacity (NIAC), were significantly higher than those of CK-SDF. However, the dense structure and high crystallinity of A-SDF resulted in a significantly lower GAC and NIAC than that of CK-SDF, with only WHC and α-AAIR being improved. Overall, this study showed that HTCU and HTCE could be used as ideal modification methods for MCBR SDF, HE-SDF and HU-SDF have potential as functional additives in food.

Optimization of fermentation for γ-aminobutyric acid (GABA) production by yeast Kluyveromyces marxianus C21 in okara (soybean residue)

γ-Aminobutyric acid (GABA) is a non-protein amino acid with a variety of physiological functions. Recently, yeast Kluyveromyces marxianus strains involved in the catabolism and anabolism of GABA can be used as a microbial platform for GABA production. Okara, rich in nutrients, can be used as a low-cost fermentation substrate for the production of functional materials. This study first proved the advantages of the okara medium to produce GABA by K. marxianus C21 when L-glutamate (L-Glu) or monosodium glutamate (MSG) is the substrate. The highest production of GABA was obtained with 4.31 g/L at optimization condition of culture temperature 35 °C, fermentation time 60 h, and initial pH 4.0. Furthermore, adding peptone significantly increased the GABA production while glucose and vitamin B6 had no positive impact on GABA production. This research provided a powerful new strategy of GABA production by K. marxianus C21 fermentation and is expected to be widely utilized in the functional foods industry to increase GABA content for consumers as a daily supplement as suggested.

Protective Effect and Mechanism of Soybean Insoluble Dietary Fiber on the Color Stability of Malvidin-3-O-glucoside

Anthocyanins have great health benefits, especially malvidin. Vitis amurensis Rupr are rich in malvidin, and malvidin-3-O-glucoside (Mv3G) monomer is the most abundant. However, natural anthocyanins are unstable, which limits their wide application in the food field. Soybean insoluble dietary fiber (SIDF) has high stability, and it can be used as an inert substrate to construct a stable system, which may improve the stability of anthocyanins. The optimal condition to construct a stable system of SIDF and Mv3G at pH 3.0 was determined by an orthogonal experiment. The results indicated that SIDF effectively improved the stability of Mv3G under different pH values (1.0~7.0), high temperature (100 °C for 100 min), and sunlight (20 ± 2 °C for 30 d) conditions. The absorption peak intensity of the UV–VIS spectrum of SIDF-Mv3G was enhanced, which indicated that there was interaction between SIDF and Mv3G. Fourier transform infrared spectroscopy analyses revealed that the -OH stretching vibration peak of SIDF-Mv3G was changed, which indicated that the interaction between SIDF and Mv3G was due to hydrogen bonding. X-ray diffraction analysis showed that the crystalline morphology of SIDF was opened, which was combined with Mv3G, and SIDF made Mv3G change to a more stable state. Scanning electron microscope analysis showed that SIDF and Mv3G were closely combined to form an inclusion complex. Overall, this study provides valuable information for enhancing the color stability of anthocyanins, which will further expand the application of anthocyanins in the food field.

Effects of Ball Milling Combined With Cellulase Treatment on Physicochemical Properties and in vitro Hypoglycemic Ability of Sea Buckthorn Seed Meal Insoluble Dietary Fiber

To improve the rough texture and hypoglycemic ability of sea buckthorn insoluble dietary fiber (IDF), a novel combined modification method was developed in this study. The IDF was treated with ball milling and cellulase treatment to obtain co-modified insoluble dietary fiber (CIDF). The physicochemical and functional properties of IDF, milled insoluble dietary fiber (MIDF), and CIDF were studied. After treatments, MIDF had smaller particle sizes and a looser structure, and CIDF exhibited a wrinkled surface and sparse porous structure according to scanning electron microscopy (SEM) and X-ray diffraction. Compared to IDF, MIDF and CIDF showed improved water-holding, oil-binding, and swelling capacities, improved by 16.13, 14.29, and 15.38%, and 38.5, 22.2, and 25.0%, for MIDF and CIDF, respectively. The cation exchange ability of modified samples showed improvement as well. Treatments also changed the fluidity of MIDF and CIDF. Due to the smaller particles and increased stacking, the bulk density (BD) and angle of repose of MIDF improved by 33.3% and 4.1° compared to IDF, whereas CIDF had a looser structure and thus decreased by 7.1% and 13.3° with increased fluidity. Moreover, the modification also enhanced the effects of CIDF on glucose adsorption, glucose diffusion inhibition, starch digestion inhibition, starch pasting interference, and α-amylase activity inhibition. In summary, IDF modified by ball milling combined with cellulose treatment could be developed as a functional ingredient for regulating glucose content.

Characteristics of lipoxygenase-based and lipoxygenase-deficient soy yogurt with modified okara

Lipoxygenase-based and lipoxygenase-deficient okara were modified by Kluyveromyces marxianus fermentation, then adding modified okara back to the corresponding soymilk to prepare soy yogurt. The physicochemical properties, texture, and volatile components of soy yogurt were characterized. The results showed that okara modified by Kluyveromyces marxianus fermentation was rich in soluable dietary fiber and was imparted better water-holding capacity, swelling capacity, and oil-holding capacity. The soy yogurt with the modified okara was greatly enhanced in its appearance, texture and was relatively stable during storage. Moreover, lipoxygenase-based soy yogurt had a unique soybean flavor while lipoxygenase-deficient soy yogurt had a slight beany flavor and soybean flavor. This article guides a bio-modified method for okara and provides a theoretical basis for the further development and application of soy yogurt with high dietary fiber as well as lipoxygenase-deficient soy yogurt.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-01003-w.

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.

Effects of ultrasonic treatment and homogenization on physicochemical properties of okara dietary fibers for 3D printing cookies

This paper presents a means to modify the attributes of okara fiber using ultrasonic and high-speed shearing treatment. The results of scanning electron microscopy and differential scanning calorimetry reveal that the modified okara fiber demonstrates small particle size and high thermal stability. When the 500 W-15,000 rpm combination is used for okara-fiber treatment, the latter exhibits excellent swelling (SC) as well as water- and oil-holding capacities. When 6% of modified okara fiber is added to the dough, the resulting cookies demonstrate the best printing performance. Subsequently, the printing parameters can be optimized to obtain the best filling rate of 30%. The corresponding nozzle diameter and printing speed equal 0.8 mm and 50 mm/s, respectively. Finally, the 3D-printed cookies containing okara fiber are compared against those commonly available in the market via sensory evaluation. As observed, the 3D-printed cookies were more acceptable to people. Therefore, the addition of the okara dietary fiber to the cookie dough not only improves the okara utilization rate but also increases the dietary-fiber content in the cookie, thereby alleviating the occurrence of obesity in modern society.

Statistical Approach to Potentially Enhance the Postbiotication of Gluten-Free Sourdough

Fermented products are permanently under the attention of scientists and consumers, both due to nutritional importance and health promoting effects. The fermented functional foods contribute to a more balanced diet and increase the immune responses (among many other health effects) with positive implications for quality of life. In this sense, improving the sourdough’s fermentation to boost the biotic (postbiotic and paraprobiotic) properties of the sourdough-based products has positive impacts on the nutritional and functional properties of the final baked products. These enhanced sourdoughs can be obtained in controlled fermentation conditions and used as sourdough bread improvers or novel bioingredients. In this context, our work aimed to optimize, using statistical tools, a gluten-free sourdough based on chickpea, quinoa, and buckwheat fermentation with selected lactic acid bacteria (LAB) to enhance its postbiotic properties. The most important biotechnological parameters were selected by Plackett–Burman Design (PBD) and then Response Surface Methodology (RSM) was applied to evaluate the interactions between the selected factors to maximize the gluten-free sourdough’s properties. As a result, the optimized fermented sourdough had antimicrobial activity with inhibition ratios between 71 and 100% against the Aspergillus niger, Aspergillus flavus, Penicillium spp. molds and against the Bacillus spp endospore-forming Gram-positive rods. The optimized variant showed a total titratable acidity (TTA) of 40.2 mL NaOH 0.1N. Finally, the high-performance liquid chromatography (HPLC) analysis highlighted a heterofermentative profile for the organic acids from the optimized sourdough. Among flavonoids and polyphenols, the level of caffeic and vanillic acids increased after lactic acid fermentation. The comparison between the optimized sourdough and the control evidenced significant differences in the metabolite profiles, thus highlighting its potential postbiotication effect.