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Aims:  The aim of this study was to investigate changes in Salmonella and total viable count (TVC) survival on beef carcass surfaces stored for 72 h under different combinations of relative humidity (i.e. RH 75% or 96%) and temperature (5°C or 10°C). Methods and Results:  The influence of low water activity (aw) and temperature on the survival and growth of Salmonella enterica serovar Typhimurium DT104 and the aerobic mesophilic flora on meat pieces from different sites on beef carcasses was investigated, under controlled conditions (75% or 96% RH; 5 or 10°C) in an environmental cabinet. Salmonella counts declined during storage at low aw (75% RH) conditions at 5°C or 10°C. Salmonella counts increased during storage at high aw (96% RH) at 10°C only. At 5°C, TVCs increased during storage at high aw, but not at low aw. TVCs increased on all samples from carcasses stored at high or low aw at 10°C, except those samples taken from areas of surface fat. Conclusions:  This suggests that substrate composition dictates growth rates under low aw conditions. The results are discussed in terms of the possible protective effects of substrate osmolyte accumulation in bacterial survival and/or growth. Significance and Impact of the Study:  The data obtained in this study provides useful insights on the influence of aw and temperature on pathogen survival on meat surfaces at chill temperature.

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Aims:  To determine the effectiveness of a novel dry air decontamination apparatus in the deactivation of Salmonella serotype Typhimurium DT104 or Escherichia coli O157:H7 on beef surfaces. Methods and Results:  A laboratory scale dry air decontamination apparatus, capable of producing repeatable and known heating time–temperature cycles on food surfaces was used in decontamination trials. Beef samples were surface inoculated with 7–8 log10CFU cm−2 of S. Typhimurium DT104 or E. coli O157:H7 and heated at 60, 75, 90 and 100°C using fast and slow heating rates and subsequently held at these temperatures for up to 600 s. A substantial reduction in pathogen numbers was achieved at higher temperatures (90 and 100°C, 4·18–6·06 log10CFU cm−2) using both heating rates, but cell survival at these temperatures was also observed. At the lower temperatures, deactivation was small at 60°C in particular it was less than one log unit after 3 min heating. No significant differences were observed when total reductions in pathogen counts were compared for all the temperature/heat up time combinations tested. During slow heating at 90°C, and both heating rates at 100°C, the pattern of deactivation of S. Typhimurium DT104 or E. coli O157:H7 was triphasic. Conclusions:  This study has shown that heating meat surfaces with dry air can achieve substantial reductions in S. Typhimurium DT104 or E. coli O157:H7. As surface decontamination of beef surfaces with dry air had a negative effect on beef colour and appearance, such a decontamination apparatus would be unsuitable for producing meat for retail sale but it could be used to produce safer meat for use in the catering trade. Significance and Impact of the Study:  This study provides researchers and food processors with data on the dynamic changes in S. Typhimurium DT104 and E. coli O157:H7 counts on intact beef surfaces during heating with dry air under realistic (time‐varying) temperature conditions.