Continuous inactivation of alkaline phosphatase and Escherichia coli in milk using compressed carbon dioxide as inactivating agent

This work investigated a continuous processing of milk for inactivation of alkaline phosphatase and Escherichia coli ATCC 25922 using supercritical carbon dioxide as inactivating agent. For this purpose, the influence of CO2 to milk mass ratio in the range of 0.05-0.45 wt%, temperature from 30 to 70 °C, pressure from 80 to 180 bar and apparent residence time from 10 to 30 min on the enzyme and microbial inactivation were investigated by means of a central composite design for three independent variable. Enzyme inactivation of 94.5% was reached when the process was operated at CO2 to milk mass ratio of 0.05, 70 °C, 80 bar and apparent residence time of 30 min. At this condition, the rate of microbial inactivation was 0.09 min−1. Results presented in this work contribute for the development of innovative process for food processing and preservation. The continuous operation consists in an advance in the use of supercritical carbon dioxide for food treatment.