Effects of High Pressure Processing and Hot Water Pasteurization of Cooked Sausages on Inactivation of Inoculated Listeria monocytogenes, Natural Populations of Lactic Acid Bacteria, Pseudomonas spp., and Coliforms and Their Recovery during Storage at 4 and 10 degrees C

The study investigated the effects of high pressure processing (HPP; 600 MPa for 3 min) and hot water (HW; 75 degrees C for 15 min) pasteurization on the inactivation of inoculated Listeria monocytogenes, natural populations of lactic acid bacteria, Pseudomonas spp., and conforms in vacuum-packaged cooked sausages and their recovery during storage at 4 and 10 degrees C for 35 days. Cooking sausages to an internal temperature of 72 degrees C resulted in a >6-log reduction in numbers of inoculated L. monocytogenes. Storage at 4 degrees C resulted in no significant difference (P > 0.05) in L. monocytogenes numbers in sausages pasteurized by either HPP or HW compared with unpasteurized control. However, at 10 degrees C, L. monocytogenes numbers in unpasteurized control sausages increased to about 7 log CFU/g by day 35, whereas in HPP-pasteurized sausages, numbers remained below the detection limit for up to 21 days and then increased to 4.5 log CFU/g by day 35. HW pasteurization resulted in inhibition of L monocytogenes to below the detection limit throughout the 35-day storage at 10 degrees C. Natural lactic acid bacteria populations were significantly reduced by HPP and HW pasteurization and continued to be significantly lower at the end of the 35-day storage. Unlike most studies that focus on HPP or HW treatment of postcooking surface contamination of meat with Listeria, this study examined the combined effect of cooking, HPP, and HW on raw meat with a high contamination level. This scenario is important in countries where raw meat supply and in-store refrigeration are a challenge. The results suggest that HPP and HW pasteurization could be used to successfully enhance the safety and shelf life of cooked sausages and that HW pasteurization (75 degrees C) was more effective than HPP (600 MPa) to control L. monocytogenes.