High pressure processing of apple juice: the most effective parameters to inactivate pathogens of reference

High-acid liquid foods are a substrate in which foodborne pathogens can maintain their viability. In this research an experimental design was conducted to optimize the parameters for high pressure processing (HPP) of apple juice (pH 3.76).

Juice was inoculated with cocktails of Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes. Pressures ranging from 139 to 561 MPa and dwell times between 39 and 181 s were challenged.

Pressures above 400 MPa achieved a greater than 5-log reduction in all pathogen cocktails regardless of the dwell time. L. monocytogenes was more sensitive to HPP at a pressure of 350 MPa and dwell times equal to or beyond 110 s. E. coli O157:H7 and S. enterica exhibited similar resistance; the number of log reductions in the central point (350 MPa/110 s) ranged from 2.2 to 3.7. The first-order mathematical model better fitted experimental data for E. coli O157:H7 and S. enterica. In regard to L. monocytogenes, the second-order model better fitted this pathogen's reduction.

Fruit juices are usually high pressure processed at approximately 600 MPa. For pathogenic reduction, the use of milder parameters may save energy and maintenance costs. The results herein exhibited could assist the apple juice industry with more effective applications of HPP.

The findings of this study demonstrate that relatively moderate pressures can be successfully used to assure the safety of apple juice.