Effect of Product Caliber Size and Fat Level on the Inactivation of Escherichia coli O157:H7 during the Manufacture of Dry Fermented Sausages

Introduction: Dry fermented sausage (DFS) manufacturing processes that do not utilize heat have four other options, one being the demonstration of a 5-log reduction, which have been the subject of numerous validation studies. However, an area that can be studied in more depth is the effect of product caliber size and fat level on the inactivation of E. coliO157:H7 in DFS.

Purpose: Examine the effect of product caliber size, and fat level on the inactivation of E. coliO157:H7 during the fermentation and drying of DFS.

Methods: Three separate batches of sausage consisting of two fat levels (low, 17.5%; high, 25% w/w) and three caliber size casings (32, 55, 80 mm) containing a five-strain cocktail of E. coli O157:H7 at 10⁷ CFU/g were manufactured. Sausages were subjected to fermentation and drying and were monitored for changes in E. coliO157:H7 numbers, pH, aw and M:P ratio over an 8-week period and the results were subjected to ANOVA for significance.

Results: A significant reduction in the inactivation time of E. coli O157:H7 was observed with an increase in product caliber size. Increasing casing diameter form 32 to 55 and 80 mm increased time for 5-log reduction from 32 to 39 and 53 days, respectively. Similarly, an increase in fat level leads to a significant increase in time for E. coliO157:H7 inactivation. For example increasing the fat level form 17.5 to 25.0% increased the duration form 32 to 46 days respectively. Shelf-stable M:P ratio of 1.3 was achieved on days 18, 25 and 53 for 32, 55 and 80 mm caliber size, respectively.

Significance: DFS products with higher fat level and larger caliber size will require longer processing times to achieve the 5-log reduction of E. coli O157:H7.