Fate of Escherichia coli O157:H7 During Production of Snack Sticks Made from Beef or a Venison/Beef Fat Blend and Directly Acidified with Citric or Lactic Acid

Abstract

ABSTRACT: The effectiveness of a typical production process for eliminating Escherichia coli O157:H7 in directly acidified snack sticks made with beef or a venison/beef fat blend was evaluated for formulations of different fat content (10% and 25%) and type of direct acidulant (encapsulated citric or lactic acid). Raw batter inoculated with E. coli O157:H7 to an initial level of approximately 7.1 log CFU/g was stuffed into 21‐mm casings and processed according to a thermal‐processing schedule typical of those used commercially for directly acidified sausage products (maximum internal product temperature of 68.3 °C, followed by drying and cooling). For both beef and venison/beef fat blend snack sticks, log reductions ranged from 6.2 to > 6.6 CFU/g at the end of processing. Although moderate reductions (1.5 to 2.0 log CFU/g) were achieved as a result of processing to internal product temperatures of 68.3 °C, latter stages of the process (during which products were dried and cooled) factored prominently in the overall lethality of the process, and were essential in achieving the 5‐log reduction required by the U.S. Dept. of Agriculture, Food Safety and Inspection Service. The efficacy of the process was not affected (P≤ 0.05) by fat content (10% or 25%) or by the type of direct acidulant used (encapsulated citric or lactic acid). Phenol red sorbitol agar was more effective for recovering heat‐ and acid‐injured E. coli O157 than MacConkey sorbitol agar was and, therefore, provided a more conservative estimate of process lethality.