Fate of Salmonella Species, Escherichia coli O157:H7 and Listeria monocytogenes during the Manufacture of Dry Cured Westphalian Style Ham

Introduction: Westphalian ham is a dry cured, Ready-to-Eat product that is manufactured without a lethal heat treatment. Hams are preserved by a process that involves curing with salts and spices, fermentation, smoking and drying. These processes have to be validated to successfully control the growth of pathogens.

Purpose: Examine the fate of Salmonella spp., E. coli O157:H7 and L. monocytogenes during the manufacture of dry cured Westphalian style ham.

Methods: Intact hams were surface inoculated with a three-pathogen cocktail resulting in a final population of at least 10⁸ CFU/cm² of each pathogen and held at 4°C for 24 h prior to application of a dry rub containing salt, spices and fermentation starter culture of BactoFerm® C-P-77 or BactoFerm® C-P-77 and bio-protective anti-listeria culture SafePro® B-LC-48 combined and then subjected to a 70 day process of fermentation, smoking and drying. Enumeration of inoculated pathogens, pH, a_w and total viable counts on external surfaces were performed on both inoculated and uninoculated hams before any treatment and after inoculation, salting, smoking and drying.

Results: Both Salmonella spp. and E. coli O157:H7 decreased by at least 5 log CFU/cm² regardless of the bio-protective and/or fermentation culture used. L. monocytogenes, on the other hand, decreased by 4.41 and 5.64 log CFU/cm² on hams with fermentation culture or fermentation and bio-protective culture combined, respectively. The initial 28 day salting stage had the largest effect in reduction of the inoculated pathogens. Water activity of the product decreased from 0.98 (day 1) to 0.93 (fermentation culture) and 0.90 (combined starter culture) on day 70.

Significance: The Westphalian ham production process employed in this study is adequate for the reduction of Salmonella spp., E. coli O157:H7 and L. monocytogenes by at least 4.4 to 5.5 log CFU/cm². The salting step in the manufacture process is the most crucial step in pathogen reduction.