Combined technologies of ultrasound/heat-induced inactivation of Staphylococcus aureus in liquid food

Abstract

Mild processes of foods are emerging and promising alternatives to conventional food processing, especially for decreasing deteriorative effects of preservation processes. The use of combined ultrasound and heat processing was investigated on Staphylococcus aureus, used as a model microorganism in a full-fat milk medium. Bacterial destruction rates in various conditions, including heating at 55o C and 60o C in the presence and absence of ultrasound application, presence and absence of lactic acid as pH regulator and at two initial inoculum sizes, were recorded. Combined ultrasound application, lowering the pH and lower initial inoculum size, resulted in higher bacterial destruction rates. The inactivation rate was found to be dependent on the exposure time and temperature, while larger inoculum size resulted in lower logarithmic reduction.