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The Influence of High-Power Ultrasound and Bactofugation on Microbiological Quality of Milk

Edita Juraga1orcid tiny, Višnja Stulić2*orcid tiny, Tomislava Vukušić Pavičić2orcid tiny, Jasenka Gajdoš Kljusurić2orcid tiny, Mladen Brnčić2orcid tiny and Zoran Herceg2orcid tiny

1ATERA d.o.o., Ivane Brlić Mažuranić 25, Varaždin 42 000, Croatia

2Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottjeva 6, Zagreb 10 000, Croatia

Article history:

Received: 4 February 2021

Accepted: 8 November 2021

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Key words:

milk, high-power ultrasound, microbiological safety of milk, technology of milk bactofugation


Research background. The application of high power ultrasound, combined with a slightly increased temperature on raw whole cow's milk, skimmed cow's milk, and skimmed cow's milk that passed the bactofugation process were analyzed. A combination of those techniques, ultrasound and the bactofugation of milk was conducted to achieve the microbiological accuracy that is usually achieved by the pasteurization process. 

Experimental approach. The milk samples (200 mL) were treated for 2.5, 5, 7.5 and 10 minutes 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 %. Temperature levels during the treatments were 20 and 55 °C. The count of somatic cells was analyzed for the aerobic mesophilic bacteria, as well the number of Enterobacteriaceae, Escherichia coli and Staphylococcus aureus cells.

Results and conclusions. The best result from the perspective of the reduction of the total count of bacteria was achieved by high-power ultrasound with a power of 400 W treated for 10 minutes. High reduction of Enterobacteriaceae, E. coli and S. aureus cells was achieved in ultrasound treatment of raw whole, skimmed and skimmed cow's milk with a power of 200 and 400 W regardless of a treatment time. 

Novelty and scientific contribution. High-power ultrasound with a combination of bactofugation as a pretreatment for milk and with a slightly increased temperature (up to 55 °C) is much more economical than the pasteurization process, while it preserves the sensory and physicochemical properties of milk.

*Corresponding author: +3814605035

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