Starter Culture to Inhibit Pore Formation by Heterofermentative Bacteria in Cooked Ham

Introduction: Pore formation in cooked products, such as ham, is a severe optical drawback for consumers as it is associated with a low quality product.  Pore formation can occur due to insufficient vacuum during tumbling or because of contamination with heterofermentative bacteria producing carbon dioxide (CO₂).

Purpose: A challenge test study was conducted by inoculating raw material with a cocktail of CO₂-producing spoilage bacteria in order to demonstrate how a properly selected bioprotective culture can significantly reduce the number and the size of holes in cooked ham.

Methods: Heterofermentative lactic acid bacteria isolated from spoiled cooked ham (Lactobacillus brevis) were used to inoculate pork loin at 100 cfu/g. A Lactobacillus sakei starter culture was also added into the brine before injection. Tumbling, heating (until reaching 165°F as core temperature), and cooling was then applied to mimic standard industrial ham process. Cooked ham was sliced into two mm thick slices. Slices were scanned and analyzed with ImageJ software to evaluate number and size of pores. An untrained panel was also used to evaluate the ham porosity.

Results: Starter culture L. sakei significantly reduced the number and the size of pores caused by microbial contamination of heterofermentative bacteria. Results obtained with ImageJ and the panel are linearly correlated.

Significance: These results suggested that the use of starter culture, as a processing aid, during the manufacturing of cooked meat injected products is an effective hurdle to significantly reduce holes formation due to microbial contamination and, thus, to improve the quality and appearance of the final product.