Structural and functional properties of milk proteins as affected by heating, high pressure, Gamma and ultraviolet irradiation: a review

The current review focused on the effect of different thermal and non-thermal processing techniques on the structural and functional modifications of milk proteins. In thermal processing, denaturation in whey proteins takes place at the temperature range of 60–100°C. High temperature short time (HTST) treatment caused denaturation with the loss of secondary structure of proteins at temperature of 72°C for 15 minutes. Ultra-high temperature (UHT) treatment damaged β-lactoglobulins at higher temperature range of 135–140°C for 2 seconds. High-pressure processing (HP) (≤200-400 MPa) caused denaturation and aggregation of casein micelles with large molecular size. High-pressure homogenization with 350–400 MPa caused modification in structure of milk proteins and enhanced the solubility of whey proteins. Gamma irradiation with the dose of 3 kGy and 10 kGy crosslinked bands from α-lactalbumin and β-lactoglobulins respectively. At the dose of 32–64 kGy, crosslinking among caseinates appeared and molecular size of whey proteins increased. Dose of ultraviolet (UV) irradiation (254 nm) caused stability and improvement in the structure of whey proteins. Sonication treatment (20 W for 60 minutes) caused reduction in the size of casein micelles up to 1–4 nm