Manothermosonication (MTS) treatment of apple-carrot juice blend for inactivation of Escherichia coli 0157:H7

This study was performed to evaluate the responses of Escherichia coli 0157:H7 inoculated in an apple-carrot blended juice to manothermosonication (MTS) treatments. The MTS treatments were conducted in a continuous-flow MTS system. The juice samples were exposed to ultrasound treatment at combinations of three temperatures (60, 50 and 40°C) and three pressure levels (100, 200, and 300kPa) for five residence times (15, 30, 45, 60, and 75s). The results showed that higher treatment temperature (i.e. 60°C) and hydrostatic pressure in the MTS system significantly enhanced the microbial reduction. A FDA mandated 5-logCFU/ml reduction of E. coli 0157:H7 for juice processing was achieved in 30s for MTS treatment at 60°C, in comparison to 60s at 50°C. The Weilbull and Log-logistic models provided the best fitting of the inactivation data for the MTS treatments. Extensive damage of E. coli 0157:H7 cells treated with MTS was observed on micro-images of scanning electron microscopy and transmission electron microscopy.