Influence of pH on fluid gels produced from egg and whey protein isolate

The Potential of Soluble Proteins in High-Moisture Soy Protein-Gluten Extrudates Preparation

In this study, the effects of different soluble proteins, including collagen peptides (CP), soy protein hydrolysate (HSPI), whey protein isolate (WPI), sodium caseinate (SC), and egg white protein (EWP), on the structural and mechanical properties of blends containing soy protein isolate (SPI) and wheat gluten (WG) were investigated using high-moisture extrusion. The addition of CP and HSPI resulted in a more pronounced fibrous structure with increased voids, attributing to their plasticizing effect that enhanced polymer chain mobility and reduced viscosity. WPI, SC, and EWP acted as crosslinking agents, causing early crosslink formation and decreased polymer chain mobility. These structural variations directly influenced the tensile properties of the extrudates, with CP displaying the highest anisotropic index. Moreover, the presence of soluble proteins impacts the permeability of the extrudates. These insights shed light on how soluble proteins can be used to modify the properties of SPI-WG blends, making them suitable for meat analogue production.

Effect of pH on the thermal gel properties of whey protein isolate-high acyl gellan gum

BACKGROUND

Protein-polysaccharide gels have significant and unique properties in food formulations. However, they are susceptible to environmental influences like heat and pH. The present work investigated the effects of acid and alkali treatments on the gel properties and microstructural changes of whey protein isolate (WPI) high acyl gellan gum (HG).

RESULTS

The results showed that the pH had a strong effect on the gel hardness, water-holding capacity (WHC), free sulfhydryl groups (-SH), and other properties of the composite gel. The hardness reached a maximum level of 282.50 g and the best WHC was 98.33% at pH 7, indicating that a suitable pH could promote this cross-linking between the WPI and HG molecules. The rheological analysis demonstrated that the pH affected the gel formation time. Meanwhile, the gel formation time reached a maximum at pH 7, and the gel's storage modulus G' value was the largest in the final state. Fourier transform infrared spectroscopy (FTIR) results showed that pH affected the interaction between WPI and HG. Scanning electron microscopy (SEM) analysis also indicated that the composite gel formed a three-dimensional network structure at pH 7-9.

CONCLUSION

These results could broaden the application of protein-polysaccharide gels in food and delivery systems. © 2023 Society of Chemical Industry.

Influence of Different pH Values on Gels Produced from Tea Polyphenols and Low Acyl Gellan Gum

To explore the influence of pH values on the properties of a compound system containing tea polyphenols (TPs) and low acyl gellan gum (LGG), the color, texture characteristics, rheological properties, water holding capacity (WHC), and microstructure of the compound system were measured. The results showed that the pH value noticeably affects the color and WHC of compound gels. Gels from pH 3 to 5 were yellow, gels from pH 6 to 7 were light brown, and gels from pH 8 to 9 were dark brown. The hardness decreased and the springiness increased with an increase in pH. The steady shear results showed that the viscosity of the compound gel solutions with different pH values decreased with increasing shear rates, indicating that all of the compound gel solutions were pseudoplastic fluids. The dynamic frequency results showed that the G' and G″ of the compound gel solutions gradually decreased with increasing pH and that G' was higher than G″. No phase transition occurred in the gel state under heating or cooling conditions at pH 3, indicating that the pH 3 compound gel solution was elastic. The WHC of the pH 3 compound gel was only 79.97% but the WHC of compound gels pH 6 and pH 7 was almost 100%. The network structure of the gels was dense and stable under acidic conditions. The electrostatic repulsion between the carboxyl groups was shielded by H⁺ with increasing acidity. The three-dimensional network structure was easily formed by an increase in the interactions of the hydrogen bonds.