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:  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.