2014 Volume 20 Issue 5 Pages 1043-1049
This study was conducted to investigate the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of selected essential oils (EOs) against Escherichia coli O157:H7 under neutral and acidic pH conditions, and to evaluate the efficacy of EOs on the inactivation of E. coli O157:H7 in vegetable juice samples stored at 5, 20 and 35°C or heated at 55°C. The growth and survival of E. coli O157:H7 were significantly affected by pH adjustment, additive concentration, storage temperature and time. A synergistic or hurdle effect was observed within EOs at pH 4.0 and pH 4.5, or with heat treatment. The calculated decimal reduction times (D-value, min) varied with the EOs concentration. Star anise oil (0.05%, vol/vol) provided the maximum reduction in D55 value, from 5.69 min to 0.38 min. The combination of mild heat treatment and EOs may be used to enhance the safety of juice products.