High-pressure Processing and Cultures: The Right Combination to Produce Safe Semi-dried Italian Fermented Sausages without Taste Compromise

Introduction: Listeria monocytogenes and Salmonella spp. are the two main pathogenic bacteria that pure pork sausages manufacturers must address. Here, the combination of a starter culture including a bacteriocin producing strain and high-pressure processing (HPP) were tested to obtain a sufficient log reduction during a typical Milano process.

Purpose: Challenge tests were performed to evaluate the Salmonella and Listerialog reduction during the Milano process and after the HPP treatment.

Methods: A standard 100% pork batter was obtained from an Italian producer. The meat batter was inoculated with a cocktail of Listeria innocua and Salmonella spp. and properly dosed with the starter culture before being stuffed into a 90 mm casing. Sausages were then ripened at 72/75°F (minimal pH 5.35 in 72 h/ final pH 6.0) and dried until reaching a 30% weight loss (water activity ~0.91). HPP (6,000 Bar/5 minutes/15°C) was applied after drying. Listeria, Salmonella, Lactic Acid Bacteria, coagulase-negative Staphylococcus, and Pediococcus concentrations were measured just after stuffing, at the end of the drying step, and after HPP treatment.

Results: The starter culture maintained high concentration during the salami process, as well as after HPP Treatment. The milano process, even with a gradual pH drop and slow drying process, which typically supports higher pathogenic risk, still allowed a 3.2- and 2.3-log reduction, respectively, for Salmonella spp. and L. innocua. After HPP, a total of six- and five-log reduction, respectively, for Salmonella spp. and L. innocua were achieved.

Significance: These results suggested that the combination of starter culture, including a bioprotective strain, and HPP significantly reduce pathogenic bacteria contamination. This allowed maintenance of the traditional Milano process to obtain typical flavor and achieve more food safety.