Abstract
SUMMARYResearch backgroundThe application of high power ultrasound combined with a slightly increased temperature on raw cow’s milk, skimmed cow’s milk and skimmed cow’s milk that passed the bactofugation process was analysed. We combined ultrasound with bactofugation of milk to achieve the microbiological accuracy that is equivalent to pasteurization.Experimental approachThe milk samples (200 mL) were treated for 2.5, 5, 7.5 and 10 min with high-power ultrasound (200 and 400 W) with a frequency of 24 kHz. The treatments were conducted with a constant duty cycle of 100%. Temperatures during the treatments were 20 and 55 °C. The somatic cell count of the aerobic mesophilic bacteria, as well the number of Enterobacteriaceae, Escherichia coli and Staphylococcus aureus cells were analysed.Results and conclusionsFrom the perspective of the reduction of the total count of bacteria, the best result was achieved by high-power ultrasound at 400 W treated for 10 min. High reduction of Enterobacteriaceae, E. coli and S. aureus cells was achieved with ultrasound treatment of raw, skimmed and skimmed cow’s milk that passed the bactofugation with a power of 200 and 400 W regardless of the treatment time.Novelty and scientific contributionThis work combines bactofugation and high-power ultrasound for the inactivation of microoganisms. This combination was used at a slightly increased temperature (up to 55 °C), which is much more economical than pasteurization, while it preserves the sensory and physicochemical properties of milk.
Highlights
Milk is a biological fluid that deserves special attention as the most complete natural fluid [1]
If the microbiological analysis reveals more than 105 colony forming units (CFU)/mL microorganisms in raw milk, the result indicates a lack of hygienic conditions [3], and the somatic cell count (SCC) in 1 mL must be ≤400 000, observed as a geometric average over three months
Lower count of somatic cells in untreated skimmed milk (SO) samples than in raw milk (RM) samples was observed. This is explained by the fact that the milk was col lected in a centrifugal cream separator, and that part of the somatic cells ends up in the cream. To make it easier to monitor the impact of a treatment on the SCC, a reduction expressed in percentages was calculated
Summary
Milk is a biological fluid that deserves special attention as the most complete natural fluid [1]. It is an ideal medium for the development of undesirable microorganisms [2]. To ensure the safety of food, raw milk needs to be controlled by conducting chemical and microbiological analyses which determine its quality. If the microbiological analysis reveals more than 105 CFU/mL microorganisms in raw milk, the result indicates a lack of hygienic conditions [3], and the somatic cell count (SCC) in 1 mL must be ≤400 000, observed as a geometric average over three months. The most common processes are continuous flow pasteurization and ultra-high temperature (UHT) treatment. It is extremely important to use lower temperatures with the same or higher efficiency as pasteurization and/or sterilization
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