Inhibitory effects of microencapsulated allyl isothiocyanate (AIT) against Escherichia coli O157:H7 in refrigerated, nitrogen packed, finely chopped beef

Allyl isothiocyanate (AIT) is an effective inhibitor of various pathogens, but its use in the food industry is limited by its volatility and pungency. The objective of this study was to overcome the volatility of AIT by microencapsulation and evaluate its antimicrobial effectiveness against Escherichia coli O157:117 in chopped beef. Chopped beef was aseptically prepared and inoculated with a five-strain cocktail of E. coli O157:117 to yield 4 or 8 logo cfu/g. AIT was microencapsulated in gum acacia to yield 3.7-54.8 mg AIT/g at a ratio of 1:4 and freeze dried. Microcapsules at 5% or 10% (w/w) were then added to experimental samples that were packed under nitrogen, and stored at 4 C for 18 days. Samples were analyzed for numbers of E. coli O157:147 and the aerobic mesophilic bacteria (TAC) at 3-day intervals. AIT at 4980 ppm eliminated both low and high levels of inoculated E. coli O157:117 after 15 and 18 days of storage, respectively. AIT at 2828 ppm reduced E. coli by 2.7 log(10) cfu/g by 18 days of storage. AIT levels < 1000 ppm were not more effective in reducing E. coli survival than the control treatment without AIT addition. AIT at 170-1480 ppm had negligible effects on the TAC, and while 4980 ppm kept TAC levels <= 3 log(10) cfu/g during 18 days of storage, the TAC reached 7.25 log(10) cfu/g in the control. It was found that AIT microencapsulated in gum acacia could be used in chopped refrigerated beef to reduce or eliminate large numbers of E. coli O157:H7. (c) 2005 Elsevier B.V. All rights reserved.