Physicochemical changes and age gelation in stored UHT milk: Seasonal variations

The physicochemical changes and the occurrence of age gelation during the storage of indirect UHT milk produced in different seasons in New Zealand were examined. UHT milk produced in the early season had the lowest protein and calcium contents, the smallest mean particle size when fresh, and the lowest propensity for age gelation. During storage, the changes in pH, ionic calcium concentration, particle size, and protein profiles of the milk and serum did not vary greatly between the seasons. Protein analysis indicated that the Maillard reaction and limited proteolysis occurred during the storage of UHT milk. The heat-induced aggregation among partially k-casein-depleted casein micelles might play a part in the physicochemical gelation of UHT milk during storage. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Physicochemical changes and age gelation during storage of indirect UHT milk produced in different seasons in New Zealand were examined. While fresh milk showed some differences in protein and calcium contents, mean particle size, and propensity for age gelation, the changes in pH, ionic calcium concentration, particle size, and protein profiles were not greatly varied during storage between seasons. Protein analysis indicated Maillard reaction and limited proteolysis occurring during storage, with heat-induced aggregation playing a role in physicochemical gelation of UHT milk.