Inactivation of Escherichia coli O157:H7 in apple juice and apple cider by trans-cinnamaldehyde

Abstract

This study investigated the antimicrobial effect of low concentrations of trans-cinnamaldehyde (TC) on Escherichia coli O157:H7 in apple juice and apple cider. A five-strain mixture of E. coli O157:H7 was inoculated into apple juice or cider at approximately 6.0 log CFU/ml, followed by the addition of TC (0%v/v, 0.025%v/v, 0.075%v/v and 0.125%v/v). The inoculated apple juice samples were incubated at 23 degrees C and 4 degrees C for 21 days, whereas the cider samples were stored only at 4 degrees C. The pH of apple juice and cider, and E. coli O157:H7 counts were determined on days 0, 1, 3, 5, 7, 14 and 21. TC was effective (P<0.05) in inactivating E. coli O157:H7 in apple juice and apple cider. At 23 degrees C, 0.125 and 0.075%v/v TC completely inactivated E. coli O157:H7 in apple juice (negative by enrichment) on days 1 and 3, respectively. At 4 degrees C, 0.125 and 0.075%v/v TC decreased the pathogen counts in the juice and cider to undetectable levels on days 3 and 5, respectively. Results indicate that low concentrations of TC could be used as an effective antimicrobial to inactivate E. coli O157:H7 in apple juice and apple cider.