Dados do Trabalho

Título

IMPACT OF ULTRASOUND ON THE INACTIVATION OF Bacillus cereus VEGETATIVE CELLS IN MILK: AN ALTERNATIVE FOR DAIRY INDUSTRY

Introdução

Ultrasound has been noticed due to its potential to inactivate pathogens through a physical mechanism known as acoustic cavitation without the need for high temperatures. The technique employs high-frequency sound waves to induce the formation of microbubbles that, upon collapsing, generate mechanical forces capable of rupturing the cell walls of bacteria and their spores, resulting in inactivation. Thus, this study focused on evaluating the ultrasound efficacy in reducing vegetative cells of Bacillus cereus in whole milk samples.

Material e Métodos

For this purpose, a strain of B. cereus (ATCC14579) was inoculated into pasteurized milk by 8.03 CFU/mL. The treatment was carried out using a probe ultrasound (Ultronics) with a frequency of 20 kHz and a maximum power of 500 watts, with an amplitude of 90%. This research evaluated two treatment durations: 10 and 15 minutes, collecting a sample every minute to assess microbial inactivation. Subsequently, microdroplet plating on nutrient agar was performed. The plates were incubated at 30°C for 24 hours. At the end of the incubation, the colonies were counted. The data were fitted by the Weibull primary inactivation model using the GinaFit Excell Add-in.

Resultados e Discussão

The results showed that the ultrasound treatment for 10 minutes caused a 0.32 log CFU/mL reduction for vegetative cells, presenting a time for the first decimal reduction (δ) of 8.7 minutes with a curve parameter (p) of 11.91. Conversely, extending the ultrasound treatment to 15 minutes resulted in a more substantial decrease of 0.70 log CFU/mL in vegetative cells, presenting a time for the first decimal reduction (δ) of 19,34 minutes with a curve parameter (p) of 1.85.

Conclusão

This study highlights ultrasound as an alternative method for reducing vegetative Bacillus cereus cells in milk, achieving reductions over short treatment periods. Adjustments in timing can optimize pathogen inactivation. Thus, while promising, ultrasound as a preservation technique in milk processing still requires further investigation and optimization to identify the ideal parameters that maximize the inactivation of B. cereus while preserving milk quality.