Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2010
Publication Date: 5/1/2010
Citation: Porto Fett, A.C., Call, J.E., Shoyer, B.A., Hill, D.E., Pshebniski, C., Cocoma, G., Luchansky, J.B. 2010. Evaluation of fermentation, drying, and high pressure processing on viability of Listeria monocytogenes, Escherichia coli O157:H7, Salmonella spp., and Trichinella spiralis in raw pork and/or Genoa salami. International Journal of Food Microbiology. 140:61-75. Interpretive Summary: Over the past decade or so there has been a noticeable decrease in the incidence of human illnesses associated with targeted food pathogens. During this same period, however, there have been numerous product recalls due to the presence of pathogens in our food supply in part due to our enhanced ability to recover them from foods. We have conducted several studies to improve the safety of delicatessen-type meats, as well as fermented sausage and specialty/ethnic meats. The primary objective of the present study was to validate the safety of processes used to prepare Genoa salami made from pork, namely fermentation, drying, and high pressure processing (HPP). Pathogens of concern included the microbial pathogens Listeria monocytogenes, Shiga toxin producing Escherichia coli, and Salmonella spp. as well as larvae of the parasite Trichinella spiralis. In collaboration with an industry partner, we prepared and purposefully contaminated pork and/or Genoa salami with the above mentioned 4 pathogens for subsequent processing. Our data revealed that all treatments of fermentation/drying and/or HPP were very effective at inactivating each of these pathogens.
Technical Abstract: We evaluated the effectiveness of fermentation, drying, and high pressure processing (HPP) to inactivate Listeria monocytogenes, Escherichia coli O157:H7, Salmonella spp., and Trichinella spiralis in Genoa salami produced with trichinae infected pork. In addition, we evaluated the effectiveness of using HPP to inactivate T. spiralis larvae in pig masseter tissue. In part A, Genoa salami batter (ca. 2.3 log larvae/g) prepared with trichinae infected pork was separately spiked with a multi-strain cocktail of each microbial pathogen (ca. 7.0 log CFU/g) and subsequently fermented at 20 degree C and ca. 90 to 95% RH for 6 hours and then at 27 deg and ca. 90 to 95% RH for 26 hours before being dried at 20 degree C and ca. 65 to 75% RH for 40 hours and then at 17 degree C and ca. 65 to 75% RH to/for: A) 25 days (65 mm casing), B) a target water activity of 0.92 (65 mm casing), C) 35 days (105 mm casing), or D) a target water activity of 0.94 (105 mm casing). Inactivation of L. monocytogenes, E. coli O157:H7, and Salmonella spp. after fermentation and drying ranged from ca. 1.1 to 1.3, ca. 1.1 to 2.2, and ca. 4.2 to 4.8 log CFU/g, respectively. After drying, three replicate salami samples in each of two trials for each treatment were subjected to HPP. Pressurization at 600 MPa or at 483 MPa for 1 to 12 min, reduced numbers of L. monocytogenes, E. coli O157:H7, and Salmonella spp. by an additional 1.6 to greater than or equal to 5.0, 4.7 to greater than or equal to 5.8, and 1.9 to 2.4 log CFU/g, respectively. After storage for 28 days at 4 degree C, L. monocytogenes levels decreased by up to an additional 3.0 log CFU/g, whereas an additional decrease of up to ca. 1.1 and 1.7 log CFU/g was observed for E. coli O157:H7 and Salmonella, respectively. In contrast, in each of three trials, T. spiralis was inactivated (ca. 2.3 log larvae/g) in Genoa salami by all treatments of fermentation and drying as confirmed by both microscopy and mouse bioassays. In part B, in each of two trials, 10 g portions (2 replicates per treatment) of infected pig masseter muscle (ca. 3.4 log larvae/g) were pressurized at 483 and 600 MPa for 0.5 to 5 min. T. spiralis was inactivated in pig masseter by all treatments of HPP as confirmed by both microscopy and mouse bioassays. Thus, fermentation and drying and/or HPP of contaminated Genoa salami or pork are effective for inactivating L. monocytogenes, E. coli O157:H7, Salmonella spp, and/or T. spiralis larvae. These data validate that HPP can be used both as an alternate to curing for trichinae control and as a post-process intervention to meet performance standards and/or compliance guidelines for the three microbial pathogens evaluated herein.