Evaluating Kombucha and Fruit Juice Blends for a 5-Log Reduction of Acid-Adapted Escherichia coli O157

Abstract

This study examined the survival of acid-adapted E. coli O157 in kombucha during fermentation and refrigerated kombucha mixed with fruit juices. Acidic and non-acidic kombucha mixes were fermented at 25°C using a commercially available starter culture and inoculated with a 5-strain mixture of acid-adapted E. coli O157. There was >5-log reduction in the pathogen count for both starter mixes within 7 days of fermentation. For the kombucha-juice blends at refrigerated temperature, 14 ml of lemon, apple, orange, and mango juices were mixed with 186 ml kombucha separately. The treatments were inoculated with a 5-strain mixture of acid-adapted E. coli O157 and incubated at 5°C for 14 days. >5-log reduction in the pathogen count was observed in lemon, control, and mango juice blend after 1, 3, and 14 days, respectively. The total reduction in pathogen count in the apple and orange juice blend after 14 days was 4.43 and 4.12 log CFU/ml, respectively. The inability of the kombucha fruit blend to cause a 5-log reduction of E. coli O157 suggests the need for following strict hygienic and good sanitation practices during blending and bottling for home fermenters and an approved HACCP plan for foodservice operators to ensure product safety.