Effects of simulated dry and wet chilling and aging of beef fat and lean tissues on the reduction of Escherichia coli O157:H7 and Salmonella.

The efficacy of dry and wet chilling and aging of beef as methods for the reduction of Escherichia coli O157:H7 and Salmonella on lean and fat tissues was studied. Samples were obtained from a harvest facility prior to antimicrobial interventions and were inoculated with a cocktail mixture of E. coli O157:H7 or Salmonella to achieve a target inoculation of 6 log CFU/cm(2). Wet chilled and aged samples were then suspended, sprayed (10 °C) continuously for 15 min and then sprayed for 1 min every 17 min for 17 h, and vacuum packed after 48 h. Dry chilled and aged samples were suspended in refrigeration (3 °C) with an air velocity of 0.25 m/s and a relative humidity of 80%. A large initial reduction of E. coli O157:H7 and Salmonella was observed, regardless of tissue type and chilling method. Fewer E. coli O157:H7 microorganisms were detected on wet chilled samples at 24 and 36 h; however, plate counts were higher from wet aged samples excised at 7 through 28 days. The final plate counts were 1.03 and 3.67 log CFU/cm(2) for dry and wet aged samples, respectively. Fewer E. coli O157:H7 microorganisms were detected on fat samples from each sampling time, with the exception of 28 days, compared with lean samples. Similar trends were observed in the reduction of Salmonella for chilling or aging method and tissue type, resulting in final plate counts of 1.25 and 3.67 log CFU/cm(2) for dry and wet aged samples, respectively. The findings reaffirmed wet or dry chilling and aging as potential interventions for small plants as a critical control point.