effects of in-package pasteurization on preventing spoilage in emulsion vacuum packaged sausages during refrigerated storage

Lactic acid bacteria (LAB) dominate the spoilage populations of vacuum-packaged emulsion-type sausages and other processed meats stored at refrigeration temperatures. An experimental investigation was carried out to evaluate the effectiveness of two in-package pasteurization treatments to prevent microbial spoilage in emulsion vacuum packaged sausages during refrigerated storage. D-values at 60 and 68°C for two isolated dominant LAB (Lactobacillus sakei and Lactobacillus plantarum) were determined in vitro and thermal treatments aimed to achieve a 4 log reduction in LAB. Sixty three sausage packs were divided into 3 groups: untreated packs (Control), treated at 60°C for 120 s (PAST 1) and treated at 68°C for 12 s (PAST 2). Microbial composition, pH values and sensorial changes were monitored in two-week intervals. In-package pasteurization resulted in an immediate 3.5–4.2 log CFU/g reduction in the population of LAB in PAST 1 and PAST 2 and remained at an acceptable level to the end of the experiment. On the contrary, during 84 days of cold storage, the LAB count increased significantly in the control samples and reached 9 log CFU/g. The control samples were also considered as unacceptable spoiled products after 28 days by sensorial aspects. All the pasteurized treatments also resulted resulted a significant (p < 0.05) reduction of psychrotrophic and the total mesophilic bacteria compared to the control ones. The data obtained showed that in both pasteurized groups none of the sensorial parameters were rated higher than the consumer-rejection threshold within 84 days of the study. No significant (p > 0.05) differences were observed in the number of spores, yeasts and molds between the pasteurized and control samples. It has been concluded that in-package pasteurization is an effective method without undesirable effects to prevent the spoilage caused by LAB growth and extend the emulsion vacuum packaged sausages shelf life to more than 3 months.