Explain the chemical properties of milk

Autoclaving milk, wherein temperature of around 121^oC is achieved, causes browning. The brown colour is due to the heat effecting an interaction between the casein (or amino acids) and the sugar. The process employed to heat milk also affects the changes in physico-chemical properties of milk. Research has shown that changes in certain physical and chemical properties of ultra-heated milk (95^oC to 145^oC) were much more severe when the milk was heated by indirect as compared to direct (steam injection) process. Increased browning and a greater amount of whey protein denaturation were particularly noticeable in ultra heated milk.