Quality Retention and Inhibition of Thermophiles in Milk Using a Novel 3-Stage Recyclable Batch Pasteurizer

Abstract

Milk quality decline and proliferation of microorganism can be prevented by heat-treatment. This however can denature the nutrients under excessive processing condition. There is therefore a need to selectively apply and evaluate this technology for milk pasteurization. In this research, the performance of a novel 3-stage recyclable batch milk pasteurizer operating at varying temperature (63– 71 °C), stirring speed (15 – 25 rpm) and holding time (15 sec – 30 min) was determined. The equipment has a hot water storage, pasteurization, and cooling tanks, which maintain the temperature of the pasteurized milk sample to 3–5^oC. The nutritional quality and the thermophile loads, including Streptococcus, Clostridium, Micrococcus, and Lactobacillus in the sample were determined as performance indices. The results show no significant trace of the thermophiles (p < 0.05) and a high value of the nutritional composition at 63°C, 25 rpm stirring speed and 15 min holding time. The quality of the product decreased progressively with an increase (p < 0.05) in the temperature and speed for all holding time. Thus, the equipment can be used for milk pasteurization with a reduced nutrient denaturation and thermophiles proliferation.