PHYSICOCHEMICAL CHANGES DURING STORAGE OF ULTRA HIGH TEMPRATURE PROCESSED WHOLE AND SKIMMED BUFFALO MILK

Abstract

Physicochemical changes in Ultra high temperature  (UHT) whole  and  skimmed  buffalo  milk  stored  at  10, 20  and 40°C for three months were studied. A significant decrease in pH and an increase in titratable acidity occurred during storage of  UHT whole and skimmed milk at 20 and 40°C after three months of storage. At 10°C, viscosity of milk increased to some extent whereas decrease in vicosity was observed at higher temperaures . After three months storage at 40°C, total ash and lactose contents decreased by 18.5% and 6.67% from UHT  whole  milk  and  20.93%  and  15.66%  from  UHT  skimmed milk, respectively . Similarly, decrease in casein nitrogen was 14.58% and 16.66% for lJHT whole and skimmed milk respectively , after three months storage at 40°C. On the other hand, non protei n nitrogen  and  non  casein  nitrogen  increased by 68.72% and 47 .72% i n UHT whole milk and 64.28% and 31.25% in UHT skimmed m ilk , respecti vely. However total nitrogen content of UH.T milk remained  unchanged  during  storage.  A  significant i ncrease i n  hydroxy methyl furfural (HMF) values was observed depending upon the initial concentration of lactose in both types of milk and storage conditions . These changes were also observed during storage of UHT milk at 10 and 20°C but to a lesser extent. Subjective evaluation studies showed that UHT milk stored at 10 and 20°C was organoleptically acceptable  after  three  months storage. On the other hand , sensory quality characteristics were adversely  affected  at  40°C  after  three  months storag  of UHT  whole  and  skimmed  milk