Effect of Milk Quality and Stabilizers on Some Physicochemical Properties of UHT-Milk

Abstract

Milk quality and stabilizers were investigated to revere their effects on undesirable changes in sensory of UHT milk as influenced by storage at 25°C or 37°C. The obtained results showed that the total microbial count, psychrophilic bacteria, mesophilic & thermophilic spore forming bacteria were higher in grade B (GB) milk than in grade A (GA) milk. Seven treatments were carried out with GA, GB, reconstituted full cream milk powder (FCMP), FCMP mix with GA and GB milk, meanwhile, two commercial stabilizers were separately evaluated. Mesophilic and thermophilic spore forming bacteria exhibited high scores and were found in standardized pasteurized GB milk comparing with GA milk. The type of stabilizer has no any effect on the UHT milk quality. The treatments of UHT milk made using GB milk received low levels of sensory properties (color & flavor), as well as, fat separation and sedimentation could be noted during storage when compared to that made from GA milk or FCMP. The fat separation and sedimentation were more pronounced in treatments stored at 37 °C when compared to that stored at 25°C. Results of SDS-PAGE and RP-HPLC did not show any significant differences among all treatments in proteolysis during storage period. Accordingly' the fat separation and sedimentation were not related only to proteolysis but were related to quality of milk used in processing.