Determining Critical Food Safety Factors for Safely Homebrewing Kombucha: A Study on Microbial Survivability

With the surge in popularity of kombucha tea, there has been a growing trend of individuals brewing this beverage at home. However, no consumer recipes have been evaluated by food safety Extension specialists for safety and quality. The present study aimed to determine critical food safety factors necessary for safely homebrewing kombucha. Kombucha was prepared with commercial Symbiotic Culture of Bacteria and Yeasts (SCOBY) and sugar concentrations of 26 g/L, 53 g/L, and 80 g/L prior to inoculation with surrogate organisms Escherichia coli K12, avirulent Salmonella strain (Salmonella Typhimurium strain LT2, H2S+), or Listeria innocua to yield nine treatment conditions per replicate, for a total of three replicates. Surrogate populations, titratable acidity of acetic acid (TA), and pH were monitored on Day 0, 7, and 14 of fermentation. TA increased (p<0.001) and pH decreased (p<0.001) from Day 0 to 14 for all treatments. The total mean log reductions across time period and sugar concentration observed for E. coli, Salmonella, and Listeria populations were 5.02, 5.86, and 4.26 log CFU/ mL, respectively. These findings will be used to inform a validated consumer recipe and corresponding guidance for safely brewing kombucha at home.