Survival of Spoilage and Pathogenic Microorganisms Associated with the Production of Pickled Sausages Using a Cold Fill Process
Open Access
- Author:
- Gaydos, Nelson Joseph
- Graduate Program:
- Animal Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 28, 2015
- Committee Members:
- Jonathan Alexander Campbell, Thesis Advisor/Co-Advisor
- Keywords:
- pickled sausage
cold fill
spoilage
pathogens - Abstract:
- Pickling has been used for centuries to preserve and extend the shelf life of different foods, ranging from fruits and vegetables, to eggs and meat. The pickling process inhibits microorganism growth by reducing product pH with organic acids, as well as the addition of salt to the product being pickled. Food items are suspended in a brine solution containing an organic acid, such as citric, lactic or acetic (vinegar) acid and combined with salt, spices and other preservatives, such as potassium sorbate. The majority of pickled foods undergo what is known as a hot fill process, where the brine solution is heated before being introduced to the food item. When the hot brine is applied to pre-cooked, ready-to-eat (RTE) meat sausages, the brine solution can change from clear to cloudy, becoming turbid and unappealing to consumers. To avoid these quality defects, pickled sausage manufacturers may use a cold fill pickling process. Cold fill pickling utilizes a room-temperature brine instead of a heated pickling solution and does not cause the aforementioned quality defects. Since very little is known about the safety of the cold fill pickling processes, a series of separate experiments was performed using a brine solution (5% acetic acid and 5% salt at ~22-23°C) to pickle pre-cooked, RTE beef and pork smoked sausages inoculated with various spoilage and pathogenic microorganisms. In two separate experiments, spoilage microorganisms consisting of lactic acid bacteria (LAB) (Lactobacillus curvatus and L. sakei); yeasts (Debaryomyces hansenii and Candida zeylanoides); molds (Penicillium nalgiovense and Cladosporium cladosporioides) and pathogenic bacteria (Salmonella Typhimurium, S. Senftenberg, S. Montevideo, Listeria monocytogenes, and Staphylococcus aureus) were inoculated onto RTE sausages prior to pickling. Microbial populations were evaluated initially (day 0) and up to 28 days after pickling and storage at room temperature. Other parameters, such as pH of the sausage, pH of the brine, water activity of the sausages, and percent salt of both the sausage and the brine, were measured over time. Results demonstrated that all microorganisms experienced a significant (p≤0.05) reduction within the first 24 hours of pickling. LAB populations were reduced ca. 6.58 log10 CFU/g in 7 days, while yeasts were reduced ca. 3.89 log10 CFU/g in 48 hours and molds were reduced ca. 4.09 log10 CFU/g in 24 hours. Pathogenic bacteria were reduced ca. 6.80 log10 CFU/g in 72 hours when plated on non-selective media and >6.33 log10 CFU/g when plated on selective media. Likewise, pH of sausages decreased significantly (p≤0.05) throughout the length of the study. No significant differences were observed for water activity (p=0.2062; p=0.1291), or % salt of the sausages (p=0.0640; p=0.1445) or brine (p=0.1046; p=0.3180) for all experiments. It was concluded from the observed data that the cold fill pickling process is capable of inhibiting and destroying contamination from both spoilage and pathogenic microorganisms within 24 hours after initial pickling. Parameters, such as the diameter of the sausages, casing type, and brine concentration were chosen in order to implement a worst case scenario. These results suggest that processors may experience an even more effective inhibition of spoilage and pathogenic microorganisms by using a higher concentrations of salt or acetic acid, pickle smaller diameter sausages or use natural or skinless casings, which will result in a faster penetration of the brine into the sausages and decrease in product pH. Results of these studies may provide scientific validation to manufacturers that cold fill pickled sausages in order to meet requirements for their HACCP systems and for regulatory compliance with the USDA-FSIS.