Alkali-Induced Phenolic Acid Oxidation Enhanced Gelation of Ginkgo Seed Protein

Hyaluronic acid promotes heat-induced gelation of ginkgo seed proteins

This study aimed to investigate how varying concentrations (0.01-0.5 %, w/v) and molecular weights (50, 500, 1500 kDa) of hyaluronic acid (HA) affect the physicochemical properties of heat-induced ginkgo seed protein isolate (GSPI)-HA composite gel. Incorporating HA increased viscosity (up to 14 times) and charge (up to 23 %) of GSPI-HA aggregates, while reducing particle size (up to 31 %) and improving gel texture, particularly with high molecular weight HA. However, high concentrations (0.5 %, w/v) of HA weakened gel texture. Non-covalent bonds primarily drive the formation of a continuous gel network between HA and GSPI, resulting in small pores and enhanced hydration properties. With increasing HA molecular weight, non-covalent interactions between GSPI and HA increased, leading to improved gel thermal stability. Overall, the study suggests that manipulating the molecular weight and concentration of HA can enhance the gelling properties of GSPI, leading to the development of a diverse array of GSPI-HA composite gels with varied properties.

Enhancing the properties of soy protein isolate and dialdehyde starch films for food packaging applications through tannic acid crosslinking

The utilization of naturally derived biodegradable polymers, including proteins, polysaccharides, and polyphenols, holds significant promise in addressing environmental concerns and reducing reliance on nonrenewable resources. This study aimed to develop films with enhanced UV resistance and antibacterial capabilities by covalently cross-linking soy protein isolate (SPI) with dialdehyde starch (DAS) through the incorporation of tannic acid (TA). The covalent crosslinking of TA with DAS and SPI was shown to establish a stable chemical cross-linking network. The tensile strength of the resulting SPI/DAS/15TA film exhibited a remarkable increase of 208.27 % compared to SPI alone and 52.99 % compared to SPI/DAS film. Notably, the UV absorption range of SPI/DAS/10TA films extended from 200 nm to 389 nm. This augmentation can be attributed to the oxidation of TA's phenolic hydroxyl groups to quinone under alkaline conditions, which then facilitated cross-linking with the SPI chain via Michael addition and Schiff base reactions. Furthermore, the film demonstrated robust antibacterial properties due to the incorporation of TA. Collectively, the observed properties highlight the significant potential of the SPI/DAS/10TA film for applications in food packaging, where its enhanced mechanical strength, UV resistance, and antibacterial characteristics can contribute to improved product preservation and safety.

L-Theanine Improves the Gelation of Ginkgo Seed Proteins at Different pH Levels

L-theanine (L-Th), a non-protein amino acid naturally found in teas and certain plant leaves, has garnered considerable attention due to its health benefits and potential to modify proteins such as ginkgo seed proteins, which have poor gelling properties, thereby expanding their applications in the food industry. The objective of this study was to investigate the impact of varying concentrations of L-Th (0.0%, 0.5%, 1.0%, and 2.0%) on the gelling properties of ginkgo seed protein isolate (GSPI) at various pH levels (5.0, 6.0, and 7.0). The GSPI gels exhibited the highest strength at a pH of 5.0 (132.1 ± 5.6 g), followed by a pH of 6.0 (95.9 ± 3.9 g), while a weak gel was formed at a pH of 7.0 (29.5 ± 0.2 g). The incorporation of L-Th increased the hardness (58.5-231.6%) and springiness (3.0-9.5%) of the GSPI gels at a pH of 7.0 in a concentration-dependent manner. However, L-Th did not enhance the gel strength or water holding capacity at a pH of 5.0. The rheological characteristics of the GSPI sols were found to be closely related to the textural properties of L-Th-incorporated gels. To understand the underlying mechanism of L-Th's effects, the physicochemical properties of the sols were analyzed. Specifically, L-Th promoted GSPI solubilization (up to 7.3%), reduced their hydrophobicity (up to 16.2%), reduced the particle size (up to 40.9%), and increased the ζ potential (up to 21%) of the sols. Overall, our findings suggest that L-Th holds promise as a functional ingredient for improving gel products.

Mechanical Properties, Microstructure, and In Vitro Digestion of Transglutaminase-Crosslinked Whey Protein and Potato Protein Hydrolysate Composite Gels

The production of animal protein usually leads to higher carbon emissions than that of plant protein. To reduce carbon emissions, the partial replacement of animal protein with plant protein has attracted extensive attention; however, little is known about using plant protein hydrolysates as a substitute. The potential application of 2 h-alcalase hydrolyzed potato protein hydrolysate (PPH) to displace whey protein isolate (WPI) during gel formation was demonstrated in this study. The effect of the ratios (8/5, 9/4, 10/3, 11/2, 12/1, and 13/0) of WPI to PPH on the mechanical properties, microstructure, and digestibility of composite WPI/PPH gels was investigated. Increasing the WPI ratio could improve the storage modulus (G') and loss modulus (G″) of composite gels. The springiness of gels with the WPH/PPH ratio of 10/3 and 8/5 was 0.82 and 0.36 times higher than that of the control (WPH/PPH ratio of 13/0) (p < 0.05). In contrast, the hardness of the control samples was 1.82 and 2.38 times higher than that of gels with the WPH/PPH ratio of 10/3 and 8/5 (p < 0.05). According to the International Organization for Standardization of Dysphagia Diet (IDDSI) testing, the composite gels belonged to food level 4 in the IDDSI framework. This suggested that composite gels could be acceptable to people with swallowing difficulties. Confocal laser scanning microscopy and scanning electron microscopy images illustrated that composite gels with a higher ratio of PPH displayed thicker gel skeletons and porous networks in the matrix. The water-holding capacity and swelling ratio of gels with the WPH/PPH ratio of 8/5 decreased by 12.4% and 40.8% when compared with the control (p < 0.05). Analysis of the swelling rate with the power law model indicated that water diffusion in composite gels belonged to non-Fickian transport. The results of amino acid release suggested that PPH improved the digestion of composite gels during the intestinal stage. The free amino group content of gels with the WPH/PPH ratio of 8/5 increased by 29.5% compared with the control (p < 0.05). Our results suggested that replacing WPI with PPH at the ratio of 8/5 could be the optimal selection for composite gels. The findings indicated that PPH could be used as a substitute for whey protein to develop new products for different consumers. Composite gels could deliver nutrients such as vitamins and minerals to develop snack foods for elders and children.