Effect of vacuum-thermosonication on the inactivation of Escherichia coli, Staphylococcus aureus, polyphenol oxidase and the quality parameters of soursop puree

Abstract

ABSTRACT The combined effect of vacuum, heat and ultrasound (vacuum-thermosonication, VTS) on soursop puree was investigated with regard to the viability of Escherichia coli and Staphylococcus aureus, inactivation of polyphenol oxidase and sensory quality. The VTS conditions were: vacuum (8.46, 11 and 16.93 kPa), heat (40, 45 and 50 °C), 1–3 intermittent vacuum pulses and ultrasound (24 kHz and 0.34 W/g of acoustic energy density) during 10 min. According to response surface methodology, the best conditions to obtain the highest microbial inactivation of ≥7 log CFU of inoculated E. coli and S. aureus, and reduction in polyphenol oxidase activity (94%) were 16.5 kPa vacuum, 50 °C, and three intermittent vacuum pulses for 10 min with ultrasound. The best VTS conditions did not negatively affect the quality parameters, and there were no significant changes in sensory attributes of the puree (a panel of 50 untrained judges). Therefore, we conclude that VTS appears a viable option in the processing of soursop.