Stability of different water-soluble vitamins during preparation and subsequent storage of spray dried buffalo skim milk powder

Heat treatments involved during conversion of buffalo milk into skim milk powder by spray drying process (inlet air temperature : 180-200degreesC; outlet air temperature : about 95degreesC) reduced thiamin, riboflavin, vitamin B-6, folic acid and total vitamin C by 11.57, 9.70, 13.11, 16.18 and 18.62% respectively. During one year storage of milk powder (total solids, 96.21%) at 30degreesC in sealed polyethylene bags of 500 g capacity and wrapped in brown paper bags, losses of water-soluble vitamins continued to occur and the losses were minimum for riboflavin and maximum for vitamin C. At the end of 6 months storage of skim milk powder, losses of thiamin, riboflavin, vitamin B6, folic acid and vitamin C were 5.3, 2.7, 11.5, 24.0 and 28.7% respectively. After 12 months of storage, the losses were almost doubled for riboflavin, folic acid and vitamin C and tripled for thiamin and vitamin B-6 as compared to that of 6 months.