Change in Microbial Count of Pasteurized Milk Stored for Various Times

Abstract

To prolong shelf life of pasteurized milk is of great benefit to Thai’s dairy industry. The storage life of well process and package milk from good quality raw milk was found to be longer than 21 days. The storage life was reduced to 4 days due to contamination after pasteurization by rapid increase in the amount of microorganisms. In slightly contaminated pasteurized milk, the amount of microorganisms gradually increased as keeping quality was long times. The amount of psychrotrophs, mesophiles, thermodurics and thermophiles that could spoile pasteurized milk were 2.8x10⁸ - 8.6 x 10⁸, 2.9 x 10⁸ – 9.9 x 10⁸, 1.6 x 10³ – 1.4 x 10⁵, and 4.9 x 10 – 7.0 x 10² cfu./ml. respectively. Deterioration of pasteurized milk was depended on the process of pasteurization not on seasonal changes.