Effect of high intensity ultrasound on transglutaminase-catalyzed soy protein isolate cold set gel

Abstract

The effects of high intensity ultrasound (HIU, 105-110 W/cm(2) for 5 or 40 min) pre-treatment of soy protein isolate (SPI) on the physicochemical properties of ensuing transglutaminase-catalyzed soy protein isolate cold set gel (TSCG) were investigated in this study. The gel strength of TSCG increased remarkably from 34.5 to 207.1 g for TSCG produced from SPI with 40 min HIU pre-treatment. Moreover, gel yield and water holding capacity also increased after HIU pre-treatments. Scanning electron microscopy showed that HIU of SPI resulted in a more uniform and denser microstructure of TSCG. The content of free sulfhydryl (SH) groups was higher in HIU TSCG than non-HIU TSG, even though greater decrease of the SH groups present in HIU treated SPI was observed when the TSCG was formed, suggesting the involvement of disulfide bonds in gel formation. Protein solubility of TSCG in both denaturing and non-denaturing solvents was higher after HIU pretreatment, and changes in hydrophobic amino acid residues as well as in polypeptide backbone conformation and secondary structure of TSCG were demonstrated by Raman spectroscopy. These results suggest that increased inter-molecular ε-(γ-glutamyl) lysine isopeptide bonds, disulfide bonds and hydrophobic interactions might have contributed to the HIU TSCG gel network. In conclusion, HIU changed physicochemical and structural properties of SPI, producing better substrates for TGase. The resulting TSCG network structure was formed with greater involvement of covalent and non-covalent interactions between SPI molecules and aggregates than in the TSCG from non-HIU SPI.

Changes in the structure, digestibility and immunoreactivities of glycinin induced by the cross‐linking of microbial transglutaminase following heat denaturation

“…Calcium-independent microbial transglutaminase (MTG) is an enzyme that can catalyse intra-and interacyl transfer reactions between the c-carboxyamide group of glutamine residues and the e-amino group of lysine residues in peptides or proteins (Zhang et al, 2016). As a result, e-(c-glutamyl)-lysine isopeptide cross-linking is formed (Gaspar & de Goes Favoni, 2015).…”

Ultrasound‐induced changes in physical and functional properties of whey proteins

“…With growing demand for functional agents in various food products, the application of high‐intensity ultrasound to modify certain functional properties of whey proteins as an alternative to traditional methods is a hot topic of study in food science technologies. Up to now, several studies (Hu et al ., ,b, ; Jambrak et al ., ; Sun et al ., ; Zhang et al ., ; O'Sullivan et al ., ; Xiong et al ., ; Zhou et al ., ) have shown that high‐intensity ultrasound can change physical and functional properties of several food proteins, including increasing surface hydrophobicity, emulsifying activity, emulsion stability and protein solubility, reducing viscosity, and improving gelling properties and foaming capacity. Therefore, we hypothesise that high‐intensity ultrasound has similar positive effects on WPI proteins.…”

Stability of lutein encapsulated whey protein nano-emulsion during storage

“…High intensity ultrasound is considered to be a promising technique that is relatively economical and easy to operate. Several studies have shown that ultrasound treatment can change the gelation properties of different food proteins [ 33 – 36 ], including whey protein [ 37 ]. Therefore, the objective of the current research was to generate a WPI based lutein loaded nano-emulsion system using ultra intensity ultrasound and evaluate its stability at different storage conditions.…”