Inactivation of Bacillus subtilis spores in orange juice and the quality change by high electric field alternating current

Abstract

Heat treatment is commonly used to inactivate micro-organisms in liquid foods in order to improve food safety and extend shelf life. However, using heat treatment to kill spores also thermally damages the food, which can adversely affect the flavor and lead to loss of nutrients. We have developed an apparatus to apply a high electric field alternating current (HEF-AC) that inactivates heat-resistant microbe spores in liquid food while preserving the freshness of raw food. In this study, HEF-AC was applied to inactivate Bacillus subtilis spores in fresh orange juice. As a result, B. subtilis spores were reduced four logarithmic orders of magnitude. The purpose of this work was to clarify the quality change of treated juice. To achieve this purpose, we used an ultra-high-temperature (UHT) treatment for comparison. Five selected quality components of orange juice treated with HEF-AC maintained higher values than when treated with UHT while having an equal inactivation effect.