Properties of bovine gelatin as affected by a cross-linking induced by horseradish peroxidase, glucose oxidase and glucose

Gelatin is an important protein-based hydrocolloid, providing excellent gelling properties in processed foods. Horseradish peroxidase (100 U/g protein), glucose oxidase (1 U/g protein), and glucose (0.025 mmol/g protein) were applied to cross-link bovine gelatin at 37 °C for 3 h, and the gelling properties of cross-linked gelatin were evaluated. Obviously, the cross-linking process did not change the composition of amino acids. The cross-linked gelatin had 39.2% increase in surface hydrophobicity, 54.7% increase in emulsion stability index, but 28.2% decrease in emulsifying activity index, in comparison with bovine gelatin. Laser scanning confocal microscopy observation indicated that cross-linked gelatin rather than bovine gelatin conferred better droplet stability on the generated emulsion after long-storage period of 48 h or 7 days. Moreover, cross-linked gelatin had decreased in vitro digestibility during pepsin hydrolysis (38.5%) and pepsin–trypsin hydrolysis (14.5%) than bovine gelatin. Finally, the gelling and melting temperatures of cross-linked gelatin were 2 °C higher than those of bovine gelatin. Overall, the cross-linking process of bovine gelatin led to easier gelation and improved heat resistance of the subsequently gels.