Short communication: Decimal log reductions of Salmonella Senftenberg 775 W and other Salmonella serovars in nonfat milk and powder

Abstract

This study aimed to compare the thermal resistance of Salmonella Senftenberg 775 W with other serovars of Salmonella in nonfat dry milk (NDM) and hydrated NDM. The scientific literature suggests that Salmonella Senftenberg 775 W is the most heat-resistant serovar in high-water-activity foods such as milk, but little is known about the heat resistance of Salmonella Senftenberg 775 W compared with other Salmonella serovars in low-water-activity foods such as NDM. The 5 serovars of Salmonella used in this study were Enteritidis, Montevideo, Newport, Senftenberg, and Typhimurium. The hydration of NDM was conducted at 13% (wt/vol) total solids. The NDM was inoculated with the 5 individual serovars of Salmonella and dried again to its original pre-inoculation water activity. Hydrated NDM was prepared from individually inoculated NDM. The surviving Salmonella population at predetermined time-temperature intervals were enumerated using injury-recovery medium, and the average log reductions for the individual serovars were calculated. As expected, Salmonella Senftenberg 775 W was the most heat-resistant serovar in hydrated NDM at 59°C and 65°C. However, the heat resistance of Salmonella Senftenberg 775 W was found to be lower than or comparable to that of other serovars in low-water-activity NDM at 80°C and 90°C.