Conjugation of soymilk protein and arabinoxylan induced by peroxidase to improve the gel properties of tofu

Optimization and Validation of Arabinoxylan Quantification in Gluten-Free Cereals via HPAEC-PAD Based on Design of Experiments

Arabinoxylans (AXs) are dietary fibers in monocotyledon cell walls that benefit digestive health and enhance food functionality. Despite their importance, no standardized method exists for AX quantification in gluten-free (GF) cereals. This study investigated the effect of hydrolysis parameters for AX quantification in GF cereals (maize, rice, oat) with varying AX content and nutritional profiles to address matrix effects. The effects of trifluoroacetic acid (TFA) concentration (0.25-4 M), temperature (90-127 °C), and time (1-5 h) on hydrolysis efficiency were examined, whereby temperature showed, in contrast to acid concentration and time, a pronounced influence. The design of experiment (DoE) model predicted 2 M TFA, 2.4 h, and 103 °C as the optimal conditions for maximizing AX yield without detectable monosaccharide decomposition for all varieties. This was experimentally confirmed with a deviation of less than 10%. An extensive validation confirmed the method's accuracy and reliability for this unified method.

Producing high-colloidal-stability sesame paste: structural role of stone milling-modified protein

BACKGROUND

Sesame paste faces issues with poor colloidal stability during storage, thereby affecting product quality and consumer experience. This study aimed to modify the proteins in sesame paste through stone milling and investigated the differences in stability produced in this environment, with the goal of addressing this issue.

RESULTS

As the number of grinding times increased from one to three, the median diameter of sesame paste significantly decreased from 85 to 74 μm (P < 0.05), and the centrifugal oil separation rate dropped from 9.05% to 6.82%. Rheological measurements indicated an increase in the flow behavior index (n) from 0.51 to 0.61. Confocal laser scanning microscopy results revealed a more uniform co-distribution of protein and oil when ground thrice. The β-sheet content of the protein in sesame paste increased from 52.92% to 56.34%, with enhancements in surface hydrophobicity, hydrophobic interactions and emulsification of protein. When the number of grinding times increased to five, the particle size of the sesame paste was further reduced and the β-sheet content of the protein decreased to 51.00%, while the oil separation rate increased to 7.78%.

CONCLUSION

Stone milling induces structural modifications in proteins, which in turn alter the internal structure of sesame paste, resulting in varying levels of oil separation at different grinding times. Among them, sesame paste ground thrice showed a 25% reduction in the oil separation rate and experienced minimal oil separation over 120 days, making it suitable for practical production. © 2024 Society of Chemical Industry.

Effect of Wet Fractionation Conditions and Pulsed Electric Field on Arabinoxylan and Protein Recovery from Maize

Maize wet fractionation by-products are primarily used as feed but offer potential for food applications. Arabinoxylans (AXs) and proteins are particularly valuable due to their network-forming properties, which depend on their molecular structure. This study assessed the effect of the steeping conditions (acid type and pH variation) combined with a pulsed electric field (PEF) as a strategy for recovering these polymers, while also evaluating their effect on the recovery yield, fraction composition, and key AX characteristics. The physical properties were studied in selected fractions to investigate the process-induced structural changes. Lactic acid and hydrochloric acid (pH 2.5) were most effective in enhancing AX and protein recovery in fiber-rich (FF) and protein-rich (PF) fractions, respectively, while acetic acid exhibited the lowest efficiency. However, bound polyphenols were best retained in the FF when lactic acid was used, indicating the lowest structural damage to AXs, compared to other acids and using a higher pH. Additional PEF pre-treatment significantly enhanced the release of proteins, dietary fiber, and fat from the FF while inducing physical modifications to the fractions (PF: higher protein unfolding, FF: improved water-binding, pasting when using PEF). These findings highlight the potential of optimizing the processing conditions to adjust the recovery of proteins and AXs from maize, while minimally affecting their functionality.

Nano fish bone prepared by high-energy media milling extends the shelf life of tofu during cold storage: Unlocking the restriction on water mobility

Nano fish bone (NFB) was produced by high-energy media milling. The NFB was composed of circular crystals (approximately 110 nm) and fibrous collagen/peptide. Effects of NFB on the quality and microorganisms of glucono-d-lactone (GDL)-induced tofu stored at 4 °C were investigated. Water activity, syneresis, whiteness, and total bacterial counts of the tofu without NFB increased continuously, reaching 0.977, 41.66 %, 80.28, and 4.55 log CFU/g over 7 days, respectively. Breaking force and penetration distance decreased by 12.93 and 21.79 %, respectively. Adding NFB significantly increased GDL tofu's breaking force and penetration distance during storage (p < 0.05) while decreasing water activity, syneresis, whiteness, and total bacterial counts (p < 0.05). With NFB, nuclear magnetic resonance (NMR) analysis showed reduced free water and increased immobilized water. 16S RNA sequencing revealed lower bacterial diversity and Pseudomonas abundance in NFB-treated tofu. By restraining water mobility, NFB effectively extends GDL tofu's shelf life by 2 days.

Research Progress on Tofu Coagulants and Their Coagulation Mechanisms

Tofu has captivated researchers' attention due to its distinctive texture and enrichment in nutritional elements, predominantly soybean protein. Coagulants play a critical role in promoting coagulation during tofu production, directly influencing its texture, quality, and physicochemical characteristics. Currently, the impact of coagulant characteristics on coagulation, as well as the underlying mechanisms, remain unclear. This review provides a summary of research progress on salt coagulants, acid coagulants, enzyme coagulants, novel coagulants, polysaccharide additives, and various coagulant formulations. The coagulation mechanisms of various coagulants are also discussed. Accordingly, this paper seeks to offer reliable theoretical guidance for the development of novel coagulants and the realization of fully automated tofu production.

Effect of pH, protein/polysaccharide ratio and preparation method on the stability of lactoferrin-polysaccharide complexes

In this study, carrageenan (CG), xanthan gum (XG) and locust bean gum (LBG), which can be used in infant formulas in China national standards, were selected to prepare LF-polysaccharide complexes to improve the stability of lactoferrin. The results showed that LF interacted more strongly with polysaccharides and did not affect the LF structure to a large extent when the pH and protein/polysaccharide mass ratio were 7 and 10:1 for LF-CG, 8 and 5:1 for LF-XG, 7 and 15:1 for LF-LBG. The zeta potential and fluorescence intensity of the LF-polysaccharide complexes displayed a decreasing trend with the increase in pH. When pH < 6, LF-CG and LF-XG exhibited precipitation and increased UV absorbance. Complexation between LF and CG/XG mainly attributed to electrostatic interactions, while LF and LBG form complexes based on hydrogen bonding or hydrophobic interactions. This study could provide a reference for the practical application of LF in infant formula.

Soy proteins modified using cavitation jet technology

Soy proteins are seen as a promising alternative food source for meat with environmentally friendly properties. The problem is that the functional properties of soy proteins do not meet the needs of the food industry, and some existing modification technologies have adverse effects. Recently, cavitation jet technology (CJT) has been studied because it generates high heat, high pressure, strong shear and strong shock waves. This review summarizes the history and mechanism of cavitation jets. The energy generated during the cavitation jet process can open molecular structures, and the shock waves and microjets generated can pulverize the materials by erosion. The impact of the CJT on the morphology, structure, and functionality of soy proteins is discussed. The impact of combining CJT with other techniques on the production of soy proteins was also reviewed. The modification of proteins using two or more methods with complementary strengths, avoiding the disadvantages of certain techniques, makes the modification of proteins more effective. One of the most prominent effects is the combined treatment of cavitation jets with physical techniques. Finally, the review provides a comprehensive analysis of the application of modified soy proteins in the food industry and highlights promising avenues for future research.

Gelling properties of acid-induced tofu (soybean curd): Effects of acid type and nano-fish bone

The effects of different types of acid coagulants and nano fish bone (NFB) additives on the characteristics of tofu were investigated using texture analyzers, SEM, FT-IR, and other techniques. The breaking force and penetration distance, in descending order, were found in the tofu induced by glucono-d-lactone (GDL) (180.27 g and 0.75 cm), citric acid (152.90 g and 0.74 cm), lactic acid (123.33 g and 0.73 cm), and acetic acid (69.84 g and 0.58 cm), respectively. The syneresis of these tofu samples was in the reverse order (35.00, 35.66, 39.66, and 44.50%). Lightness and whiteness were not significantly different among the different samples. Regardless of the acid type, the soluble calcium content in the soybean milk was significantly increased after adding NFB. As a result, the breaking force and penetration distance of all tofu samples increased significantly, but the syneresis decreased. Compared with tofu coagulated by other acids, GDL tofu formed a more uniform and dense gel network maintained by the highest intermolecular forces (especially hydrophobic interactions). Regarding the secondary structure, the lowest percentage of α-helix (22.72%) and, correspondingly, the highest β-sheet (48.32%) and random coil (18.81%) were noticed in the GDL tofu. The effects of NFB on the tofu characteristics can be explained by the changes in the gel network, intermolecular forces, and secondary structure, which were in line with the acid type. The characteristics of acid-induced tofu can be most synergistically improved by coagulation with GDL and NFB.

AIE fluorogen-based oxidase-like fluorescence nanozyme-integrated smartphone for monitoring the freshness authenticity of soy products

Food safety concerns about the authenticity of soy product freshness have increased due to high demand from public. Developing an accurate and convenient monitoring method for freshness authenticity is crucial for safeguarding food safety. From this motive, this study employed PtPd NPs to encapsulate tetraphenylethylene (TPE) for engineering an AIE-based fluorescent nanozyme (PtPd NPs@TPE) with oxidase-like activity, achieving the ratiometric fluorescence monitoring of putrescine (PUT) to judge the freshness authenticity of soy products. In this design, PUT acted as an antioxidant and inhibited the oxidation process of PtPd NPs@TPE to o-phenylenediamine (OPD), leading to the reduction of oxidative product 2,3-diaminophenothiazine (DAP) alone with the weaken of yellow fluorescence from DAP at 552 nm and bright of bule fluorescence from PtPd NPs@TPE at 442 nm. On this basis, a ratiometric fluorescence strategy integrated with smartphone-based sensor was developed for PUT with acceptable results to combat food freshness fraud of soy products.

Effect of polysaccharide concentration on heat-induced Tremella fuciformis polysaccharide-soy protein isolation gels: Gel properties and interactions

The formation of a single soybean protein isolate (SPI) gel is limited by the processing conditions, and has the disadvantages of poor gel property, and it is usually necessary to add other biomacromolecules to improve its property. In this study, we investigated the effects of polysaccharide concentration on gel properties and interaction mechanisms of Tremella fuciformis polysaccharide (TFP)-SPI complexes. It was found that (1) the rheological properties, texture properties, water-holding properties, and thermal stability of TFP-SPI composite gels were improved with the addition of TFP (0.25-2.0 %, w/v) in a concentration-dependent manner; (2) hydrogen bond, the electrostatic interaction, hydrophobic interaction, and disulfide bond in the gel system increased with the increase of TFP concentration; (3) the electrostatic and hydrophobic interactions played an important role in the formation of the TFP-SPI composite gel while hydrogen bond formation was the least contributor to the binary composite gel network. Overall, TFP is not only a critical health food but also a promising structural component for improving the gel properties of SPI.