Effect of pasteurization temperature on the keeping quality of whole milk

Summary The keeping quality (KQ) of whole milks pasteurized at 72 °C, 78 °C or 83 °C for 20 s and stored at 12 or 7 °C was examined by assessment of the naturally contaminating thermoduric microflora and of the numbers of Gram-negative rods, a single strain of the latter being introduced deliberately by post pasteurization inoculation. A pasteurization temperature of 83 °C reduced the KQ at 7 °C by about 15% compared with pasteurization at 72 °C or 78 °C, with a 2 d loss in the absence, and aid loss in the presence, of the post pasteurization contamination. The KQ of milks stored at 12 °C was not significantly affected by the pasteurization temperature. Milks pasteurized at 78 °C tended to have a slightly better KQ than those pasteurized at 72 °C, especially at 7 °C. However, pasteurization at both 78 °C and 83 °C caused a reduction in cream rising and considerably increased the risk of cream plugging.