The objective of this study was to evaluate the effect of ultrasound treatment on the microbiological quality, protein and free amino acid profile of fresh and frozen stored semi-skimmed sheep milk. Milk was treated as fresh or frozen and stored up to one, three and six months. Output power time and pulse time were the parameters combined to design four different ultrasound (US) treatments: power 78 W and duration 6 min (US1); power 78 W and duration 8 min (US2); power 104 W and duration 4 min (US3) power 104 W and duration 6 min (US4). Pulse duration was of 4 s for each treatment. Sample US1 was discarded due to non effectiveness of US treatment, while other samples showed interesting results. Also, it was verified a frost effect on microorganisms in all samples which were frozen before treatment. No relevant change was reported on amino acid profile. The study showed promising results: the ultrasound treatment inactivated or eliminated the studied contaminant bacteria in semi-skimmed sheep milk, while maintained acceptable amount of lactic bacteria, which could be advantageous for dairy products processing.

这项研究的目的是评估超声处理对新鲜和冷冻储存的半脱脂羊奶的微生物质量，蛋白质和游离氨基酸谱的影响。牛奶被当做新鲜或冷冻处理，最多可保存1、3和6个月。输出功率时间和脉冲时间是组合设计四种不同超声（US）处理的参数：功率78 W和持续时间6 min（US1）；功率78 W，持续时间8分钟（US2）；功率104 W，持续时间4分钟（US3）功率104 W，持续时间6分钟（US4）。每次治疗的脉冲持续时间为4 s。由于US处理无效，样品US1被丢弃，而其他样品显示出有趣的结果。另外，还证实了对所有在处理前冷冻的样品中的微生物都具有霜冻作用。氨基酸谱上没有相关变化的报道。这项研究显示出令人鼓舞的结果：超声处理可以灭活或消除半脱脂羊奶中研究的污染物细菌，同时保持可接受数量的乳酸菌，这可能对乳制品加工有利。