Application of reuterin produced by Lactobacillus reuteri 12002 for meat decontamination and preservation

Lactobacillus reuteri strain 12002 was used for reuterin production in the two-step fermentation process. A batch culture fermentation was used to pro duce a maximum biomass of L. reuteri. Then cells were harvested, resuspende d in a glycerol-water solution, and anaerobically incubated to produce reut erin. The lyophilized supernatants (approximately 4000 activity units (AU) of reuterin per mi) were diluted in distilled water for decontamination and preservation trials. The MIC values of reuterin for Escherichia coli O157: H7 and Listeria monocytogenes were 4 and 8 AU/ml, respectively. In meat dec ontamination experiments, the surface of cooked pork was inoculated with ei ther L. monocytogenes or E. coli O157:H7 at a level of approximately log(10 ) 5 CFU/cm(2), incubated for 30 min at 7 degrees C, and decontaminated by e xposure to reuterin (500 AU/ml). The bactericidal effect of reuterin was an alyzed 15 s and 24 h after exposure at 7 degrees C. After 15 s of exposure to reuterin, viable numbers decreased by 0.45 and 0.3 log(10) CFU/cm2 for E . coli O157:H7 and L. monocytogenes, respectively. After 24 h the numbers d ecreased by 2.7 log(10) CFU/cm(2) for E. coli O157:H7 and by 0.63 log(10) C FU/cm(2) for L. monocytogenes. In the same experiment, the combined effect of reuterin and lactic acid was also investigated. Adding lactic acid (5%, vol/vol) to reuterin significantly enhanced (P less than or equal to 0.05) the efficacy of reuterin. No additional effect (P less than or equal to 0.0 5) was found when ethanol (40%) was added to the mixture of reuterin and la ctic acid. To evaluate the preservative effect of reuterin during meat stor age, reuterin was added to raw ground pork contaminated with E. coil O157:H 7 or L. monocytogenes. Reuterin at a concentration of 100 AU/g resulted in a 5.0-log(10) reduction of the viability of E. coli O157:H7 after 1 day of storage at 7 degrees C. Reuterin at a concentration of 250 AU/g reduced the number of the viable cells of L. monocytogenes by log(10) 3.0 cycles after 1 week of storage at 7 degrees C.