Inactivation of Microorganisms in Liquid Foods by High Electric Field Alternating Current

Abstract

Heat treatment is commonly used to inactivate microorganisms in liquid foods in order to improve food safety and extend shelf-life. However, using heat treatment to kill heat-resistant microbial spores also thermally damages the food, which can adversely affect the flavor and lead to loss of nutrients. We have developed an apparatus for applying high electric field alternating current (HEF-AC), which inactivates not only vegetative cells but also spores in liquid foods while preserving the freshness of raw fruit. In this study, HEF-AC was applied to inactivate Alicyclobacillus acidoterrestris spores in fresh juice. As a result, A. acidoterrestris spore numbers were reduced by four logarithmic orders of magnitude. The purpose of this study was to clarify qualitative changes in treated juice, and an ultra-high-temperature (UHT) treatment was employed for comparison purposes. Quality parameters of orange juice treated with HEF-AC maintained higher values compared to UHT treatment; meanwhile, the two treatments showed an equal inactivation effect. Notably, lemon juice treated with HEF-AC has been commercially available since 2014 from POKKA SAPPORO Food & Beverage Ltd.