Single and sequential treatment of beef tissue with lactic acid, ammonium hydroxide, sodium metasilicate, and acidic and basic oxidized water to reduce numbers of inoculated Escherichia coli O157:H7 and Salmonella Typhimurium.

摘要

This study was conducted to determine if several potential decontamination intervention solutions, applied either singly or sequentially onto beef tissue, could effectively reduce numbers of inoculated Escherichia coli O157:H7 and Salmonella typhimurium. Samples (5x2.5x1 cm) of boneless beef plates were inoculated (~105 CFU/cm2) with four-strain composites of E. coli O157:H7 or S. typhimurium and dipped (5 pieces in 1.5 l for 30 s at 23 degrees C, unless otherwise indicated), either singly or sequentially into all possible combinations of two of the following solutions: acidic oxidative water (AOW; 0.005%, pH 2.67); basic oxidative water (BOW; pH 11.21); lactic acid (LA; 2.5%, pH 2.12 at 55 degrees C); ammonium hydroxide (AH; 0.1%, pH 10.89); sodium metasilicate (SM; 4%, pH 12.35 at 82 degrees C); or distilled water (W, pH 7.01). In phase II, an approach incorporating sequential treatments that could be applied in commercial beef harvesting plant multiple-hurdles systems was evaluated. That system included sequential dipping in 1% SM (82 degrees C), hot (82 degrees C) water, and 5% LA (55 degrees C), followed by 5% LA (55 degrees C) after 48 h (at -3 degrees C for 10 h and 1 degrees C for 38 h) of simulated carcass spray-chilling (by overhead misting of the inoculated product surface every 30 min for the first 10 h by use of a handheld sprayer). Additional systems ranged from no dipping steps to four sequential dipping steps using combinations of 1% SM (82 degrees C), 5% LA (55 degrees C), warm (55 degrees C) or hot (82 degrees C) water. Treatments, individual or in combinations, W, AOW, BOW or AH resulted in minimal decontamination (0.1-0.4 log CFU/cm2) compared with treatments using 2.5% LA at 55 degrees C and 4% SM at 82 degrees C. In general, pathogen reductions via the multiple-hurdles approach were separated into two groups with respect to efficacy: those treatments with one or more hot (82 degrees C) application or a single 5% LA application were less effective than those combining two 5% LA applications or at least one hot (82 degrees C) and one 5% LA application.