Control of Escherichia coli O157:H7 with sodium metasilicate.

Three intervention strategies-trisodium phosphate, lactic acid, and sodium metasilicate--were examined for their in vitro antimicrobial activities in water at room temperature against a three-strain cocktail of Escherichia coli O157:H7 and a three-strain cocktail of "generic" E. coli. Both initial inhibition and recovery of injured cells were monitored. When 3.0% (wt/wt) lactic acid, pH 2.4, was inoculated with E. coli O157:H7 (approximately 6 log CFU/ml), viable microorganisms were recovered after a 20-min exposure to the acid. After 20 min in 1.0% (wt/wt) trisodium phosphate, pH 12.0, no viable E. coli O157:H7 microorganisms were detected. Exposure of E. coli O157:H7 to sodium metasilicate (5 to 10 s) at concentrations as low as 0.6%, pH 12.1, resulted in 100% inhibition with no recoverable E. coli O157:H7. No difference in inhibition profiles was detected between the E. coli O157:H7 and generic strains, suggesting that nonpathogenic strains may be used for in-plant sodium metasilicate studies.

Microbiological Quality of Raw Ground Chicken Processed at High Isostatic Pressure.

Freshly ground raw chicken that had average aerobic and anaerobic bacterial populations of about 106 colony-forming units (CFU)/g was packaged and sealed in polyfilm pouches. Pouches were shipped on ice for high-pressure processing at ambient temperatures. Temperatures during the l0-min high-pressure treatment never exceeded 28°C. Samples were immediately cooled to <4°C and returned to the originating laboratory where counts of aerobic and anaerobic bacteria were made during storage at 4°C. Samples were considered spoiled at the time counts by either of the two bacterial enumeration methods reached 107 CFU/g, based on the upper limit of the 95% confidence interval of the three trials. Applications of 408 MPa, 616 MPa and 888 MPa to the samples resulted in estimated microbial spoilage times of 27 days, 70 days, and >98 days, respectively. The type of bacteria that survived best in the pressure-treated samples were the facultatively anaerobic psychrotrophic bacteria, Carnobacterium divergens and Serratia liquefaciens .