RESUMEN
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 78â¯W and duration 6â¯min (US1); power 78â¯W and duration 8â¯min (US2); power 104â¯W and duration 4â¯min (US3) power 104â¯W and duration 6â¯min (US4). Pulse duration was of 4â¯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.