Explain holding method of pasteurization

In the holding method of pasteurization (62^oC for 30 minutes) or the high-temperature short-time (HTST), 71^oC for 15 minutes methods - very little cooked flavour is noticed, but at higher temperatures or longer periods of heating, cooked flavour becomes more apparent. The flavour appears at 70^oC on momentary heating. 

This cooked flavour has been shown to be due to the production of  sulfhydryls (compounds with a -SH group, found in many  plant and animal enzymes) by high temperatures. Sulfhydryl compounds are readily oxidized and delay the oxidation of fat in milk or cream heated to high temperatures.  Oxidized flavors in milk do not usually appear until the sulfhydryls are oxidized and the cooked flavor has disappeared.