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Background: Gluten‐free bread (GFB) has technical bottlenecks such as hard texture, rough taste and low nutrition in practical production. In order to solve these problems, this study used germinated brown rice starch as the main raw material, and investigated the effects of soybean isolate protein (SPI) on the multiscale structure of germinated brown rice starch and bread quality. Results: A gluten‐free rice bread process simulation system was established, and the interaction between SPI and starch in the simulation system was characterized. The result shows that the interaction forces between SPI and germinated brown rice starch were mainly represented by hydrogen bonds, and with the addition of SPI, the crystallinity of starch showed a downward trend. At the same time, when the amount of SPI was 3%, the appearance quality was the best and the specific volume of bread was 1.08 mL g−1. When the amount of SPI was 6%, the texture quality was the best. Compared with the bread without SPI, the hardness of the bread with 6% SPI was reduced by 0.13 times, the springiness was increased by 0.03 times, the color was the most vibrant, the L* value being 1.02 times the original, and the baking loss was reduced to 0.98 times the original. Conclusions: The interaction force between SPI and germinated brown rice starch and its effect on bread quality were clarified, and these results inform choices about providing a theoretical basis for the subsequent development of higher‐quality GFB. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study explored the denaturation of 11S globulin, a protein known for its diverse functional properties in soy protein applications, at pH 3.0 and pH 10.0, followed by a gradual return to pH 7.0 to facilitate renaturation. It investigated the structural and functional changes during renaturation induced by a change in pH, revealing the stabilization mechanism of 11S globulin. RESULTS: The findings revealed that during pH adjustment to neutral, the denatured soybean 11S globulin – resulting from alkaline (pH 10.0) or acidic (pH 3.0) treatments – experienced a refolding of its extended tertiary structure to varying extents. The particle size and the proportions of α‐helix and β‐sheet in the secondary structure aligned progressively with those of the natural‐state protein. However, for the alkali‐denatured 11S, the β‐sheet content decreased upon adjustment to neutral, whereas an increase was observed for the acid‐denatured 11S. In terms of functional properties, after alkaline denaturation, the foaming capacity (FC) and emulsifying activity index (EAI) of 11S increased by 1.4 and 1.2 times, respectively, in comparison with its native state. The solubility, foamability, and emulsifiability of the alkali‐denatured 11S gradually diminished during renaturation but remained superior to those of the native state. Conversely, these properties showed an initial decline, followed by an increase during renaturation triggered by pH neutralization. CONCLUSIONS: This research contributes to the enhancement of protein functionality, offering a theoretical foundation for the development of functional soy protein products and expanding their potential applications. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: In this study, a hybrid system was prepared by mixing rice starch (RS) with different mass fractions (0%–10% dry weight) of soy protein isolate (SPI) to investigate its retrogradation characteristics during storage. The results showed that the addition of SPI led to an increase in pasting temperature and a decrease in setback (SB) and aging rate (P < 0.05). When the level of SPI was increased to 10%, the pasting temperature reached a peak of 75.28°C, resulting in a decrease of 16.52% in regrowth rate and 51.61% in aging rate. The analysis of hardness and secondary structure indicated that the inclusion of SPI resulted in a less robust starch gel structure in comparison to RS, leading to a decrease in gel hardness and the short‐range ordered structure of starch. The pore structure of the starch gel was observed to be smaller and more uniform following the addition of SPI. The presence of SPI hindered the recrystallisation of starch granules, consequently leading to a delay in starch retrogradation. The results of this study have validated the positive effect of incorporating SPI on the anti‐aging properties of starch during storage. This serves as a foundational basis for enhancing the processing attributes of RS and the overall quality of starchy food products. [ABSTRACT FROM AUTHOR]

BACKGROUND: It is well known that hemp proteins have the disadvantages of poor solubility and poor emulsification. To improve these shortcomings, an alkali covalent cross‐linking method was used to prepare hemp protein isolate‐epigallocatechin‐3‐gallate biopolymer (HPI‐EGCG) and the effects of different heat treatment conditions on the structure and emulsifying properties of the HPI‐EGCG covalent complex were studied. RESULTS: The secondary and tertiary structures, solubility, and emulsification ability of the HPI‐EGCG complexes were evaluated using particle size, zeta potential, circular dichroism (CD), and fluorescence spectroscopy indices. The results showed that the absolute value of zeta potential of HPI‐EGCG covalent complex was the largest, 18.6 mV, and the maximum binding amount of HPI to EGCG was 29.18 μmol g−1. Under heat treatment at 25–35 °C, the α‐helix content was reduced from 1.87% to 0%, and the β‐helix content was reduced from 82.79% to 0% after the covalent binding of HPI and EGCG. The solubility and emulsification properties of the HPI‐EGCG covalent complexes were improved significantly, and the emulsification activity index (EAI) and emulsion stability index (ESI) were increased by 2.77‐fold and 1.21‐fold, respectively. CONCLUSION: A new HPI‐EGCG covalent complex was developed in this study to provide a theoretical basis for the application of HPI‐EGCG in food industry. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: Rice bread is an essential component of a healthy diet. However, due to the poor processing properties of rice protein and starch, it is difficult to form an effective gel network structure, resulting in poor quality of rice breads. This research investigated the impacts of soy protein isolate (SPI) on the physicochemical properties of rice dough and the quality of rice bread. The results suggested that adding SPI could refine the thermal stability of mixtures and delay the aging of starch compared with pure rice flour, indicating that adding SPI reduced the amylose concentration and inhibited starch interaction in the mixed rice powder system. The rheology and SEM analysis of doughs showed that the appropriate addition of SPI increased the elasticity, and reached the highest fermentation height and gas retention coefficient at 9% SPI content, which increased by 115.38% and 8.39%, respectively. In contrast, excessive SPI led to protein aggregation and weakened the structural strength of the dough. When adding 9% SPI improved the hardness, chewiness and specific volume of rice bread, significantly reduced the brightness and baking loss rate, and refined the performance and quality of rice bread. This study confirms that SPI can be used as an improver for good gluten‐free bread (GFB) through its good functional properties and action on starch and provides some basis for further investigation of the interaction between SPI as an improver and rice starch. [ABSTRACT FROM AUTHOR]

BACKGROUND: This study used enzymatic and Ca2+ cross‐linking methods to prepare edible soy protein isolate (SPI) and sodium alginate (SA) interpenetrating polymer network hydrogels to overcome the disadvantages of traditional interpenetrating polymer network (IPN) hydrogels, such as poor performance, high toxicity, and inedibility. The influence of changes in SPI and SA mass ratio on the performance of SPI‐SA IPN hydrogels was investigated. RESULTS: Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the structure of the hydrogels. Texture profile analysis (TPA), rheological properties, swelling rate, and Cell Counting Kit‐8 (CCK‐8) were used to evaluate physical and chemical properties and safety. The results showed that, compared with SPI hydrogel, IPN hydrogels had better gel properties and structural stability. As the mass ratio of SPI‐SA IPN changed from 1:0.2 to 1:1, the gel network structure of hydrogels also tended to be dense and uniform. The water retention and mechanical properties of these hydrogels, such as storage modulus (G'), loss modulus (G"), and gel hardness increased significantly and were greater than those of the SPI hydrogel. Cytotoxicity tests were also performed. The biocompatibility of these hydrogels was good. CONCLUSIONS: This study proposes a new method to prepare food‐grade IPN hydrogels with mechanical properties of SPI and SA, which may have strong potential for the development of new foods. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This study investigated the effects of extrusion on the physical properties of glutinous rice and addressed the challenges associated with its hardened texture and reduced taste in glutinous rice products by adding extruded glutinous rice to assess their anti‐retrogradation effect compared with different improvers. Glutinous rice flour with different gelatinization degrees was obtained by changing the initial moisture content of glutinous rice grains before extrusion, and their physicochemical properties and the effect of adding them to rice products were analyzed. Results showed that with the increase in moisture content, the viscosity, water absorption index of extruded glutinous rice flour, and product viscosity increased, while the gelatinization degree, water solubility index, and product elasticity decreased, and the hardness of the rice products showed a trend of first decreasing and then increasing. Twenty percent moisture content of glutinous rice products showed the best properties mentioned above. The effects of adding different improvers on retrogradation degree, quality characteristics, microstructure, and moisture migration of glutinous rice products were analyzed by texture profile analysis, sensory evaluation, scanning electron microscopy, and low‐field nuclear magnetic resonance. It was found that soybean polysaccharides, xanthan gum, and extruded glutinous rice flour had better anti‐retrogradation effects, while colloid and soybean polysaccharides provided a tighter and more three‐dimensional internal structure to the rice products. Our study showed that extruded glutinous rice flour had good anti‐retrogradation properties and little effect on flavor and taste, but it would increase the roughness and viscosity of the products, which had advantages and disadvantages compared with other improvers. [ABSTRACT FROM AUTHOR]

BACKGROUND: Quinoa is a good gluten‐free resource for food processing, especially bread making, and can improve and prevent the development of complications associated with celiac disease (CD). However, lack of gluten affects quinoa bread quality. Previous research showed that soy protein isolate (SPI) could improve gluten‐free bread quality to some extent. Therefore, this study investigated the effects of SPI on the physical properties of quinoa dough and gluten‐free bread quality characteristics. RESULTS: Results showed that, with appropriate SPI substitution, the farinograph properties of quinoa flour significantly improved (P < 0.05). The sample with 8% SPI substitution showed a better development time (DT, 3.30 ± 0.20 min), stability time (ST, 8.80 ± 0.10 min) and softening degree (SD, 8.80 ± 0.10 FU), which were close to those of wheat flour, although more water absorption (WA, 76.40 ± 2.10%) was needed than for wheat flour (66.30 ± 3.10%). The extensograph properties of quinoa flour also significantly improved after 8% SPI substitution (P < 0.05). Furthermore, SPI substitution increased G′ moduli of quinoa dough and decreased tan δ to some extent, providing better rheological properties closer to those of wheat dough. SPI substitution also improved the quality and texture of quinoa bread and reduced the gap with wheat bread. When SPI substitution was 8%, the specific volume, hardness and springiness of quinoa bread were 2.29 ± 0.05 mL g−1, 1496.47 ± 85.21 g and 0.71 ± 0.03%, respectively. CONCLUSION: These results suggested that SPI substitution would be an effective way to develop higher‐quality gluten‐free bread. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]