Abstract Skim milk powders often contain high spore counts, originating from persistent thermophilic bacilli in the processing plants. Through germination and enzymatic spoilage, product defects in the reconstituted product formulation may result. Heating of skim milk concentrate prior to drying may inactivate these spores. Within this study, a new method to grow thermophilic spores isolated from dairy processing plants (Anoxybacillus flavithermus and Geobacillus stearothermophilus; N0 = 6 log10 cfu mL-1) was developed, followed by heat-inactivation experiments in reconstituted skim milk concentrate using a continuous pilot-scale microwave plant. Spore reductions were counted on tryptic-soy agar (55 °C) and formal reaction kinetics were calculated. Reductions of 1 to 3 log10 units while applying temperatures of 110–125 °C with heat holding times of 5–270 s were achieved, depending on the strain, whereby G. stearothermophilus 1978 spores were more heat resistant than the ones of A. flavithermus 1958.

中文翻译：

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连续微波加热灭活热敏感脱脂牛奶浓缩物中的嗜热孢子

摘要 脱脂奶粉通常含有高孢子数，源自加工厂中的持久性嗜热杆菌。通过发芽和酶促腐败，可能导致重构产品配方中的产品缺陷。在干燥前加热脱脂牛奶浓缩物可能会使这些孢子失活。在本研究中，开发了一种从乳制品加工厂（黄热厌氧杆菌和嗜热脂肪地芽孢杆菌；N0 = 6 log10 cfu mL-1）中分离出的嗜热孢子的新方法，然后使用连续试验对复原脱脂牛奶浓缩物进行热灭活实验规模的微波工厂。在胰蛋白酶大豆琼脂 (55 °C) 上计算孢子减少，并计算正式反应动力学。