Effect of hydrothermal treatment on the levels of selected indigenous microbes in food waste

Abstract

The ability of hydrothermal treatment to reduce or eliminate selected indicator organisms in food waste was assessed in this study. Raw food waste collected from student canteens at Tsinghua University was heat-treated under hydrothermal conditions at 90-140 °C for 10-40 min. Hydrothermal inactivation analyses were carried out on four types of indigenous microbes used as indicators of hygiene: molds and yeasts (MY), total coliforms (TC), total aerobic counts (TAC) and Staphylococcus aureus (SA). Significant reductions in the levels of indigenous microbes in food waste were achieved during the ramping and holding periods of the hydrothermal treatment, and the microbial inactivation effect increased with increasing temperature, increasing time and increasing pressure. Due to the typical properties of food waste, hydrothermal treatment at 120 °C-0.3 MPa for at least 40 min was sufficient to achieve complete sterilization of the food waste. The results showed that hydrothermal treatment could significantly reduce the levels of indigenous microbes and is a potential advanced technique for the sterilization of food waste with a high moisture content in China.