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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:

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


Research background. The 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 conclusions. From 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 contribution. This 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.

*Corresponding author: +3814605035

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