Saccharomyces cerevisiae improves rennet-induced gelation of ultra-high temperature milk

Heating milk at high temperatures impairs its renneting properties, but rennet-induced curds can be formed from ultra-high temperature (UHT) milk inoculated with Saccharomyces cerevisiae. Herein, we measured physicochemical indices of UHT milk inoculated with S. cerevisiae before rennet addition, monitored the kinetics of gel formation, and investigated the physicochemical properties and microstructure of rennetinduced curds to explore the mechanisms by which S. cerevisiae influenced rennet-induced gelation of UHT milk. Compared with untreated pasteurized cow milk and UHT milk, the ethanol content was increased, the pH was decreased, the particle size and (-potential were increased, the time points at which the elasticity index began to increase were advanced, and the maximum elasticity index was increased for UHT milk inoculated with S. cerevisiae. The number of S. cerevisiae cells affected the structure of rennet-induced curds; with few cells added, the protein network of curds was continuous and tight, the mean square displacement curves showed an asymptotic behavior, and the water retention capacity and curd yield were high; with more cells added, the loosely entangled proteins aggregated, the continuity of the network was destroyed, and the curd yield cerevisiae-inoculated UHT milk, thereby accelerating improving the renneting properties.

Automated summary

This study investigates the impact of Saccharomyces cerevisiae on rennet-induced gelation of ultra-high temperature (UHT) milk. The results show that inoculating S. cerevisiae in UHT milk leads to an increase in ethanol content, a decrease in pH, an increase in particle size and Zeta potential, as well as an advancement and increase in the elasticity index. Additionally, the number of S. cerevisiae cells affects the structure and properties of the induced curds.