Inactivation of Listeria monocytogenes and Shiga toxin-producing Escherichia coli in "soupie", a homemade soppressata

Authors: Luchansky, John; Shoyer, Brad; Shane, Laura; Osorio, Manuela; CAMPANO, STEVE - Hawkins, Inc; Porto-Fett, Anna

Submitted to: Food Protection Trends
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2021
Publication Date: 1/3/2022
Citation: Luchansky, J.B., Shoyer, B.A., Shane, L.E., Osoria, M., Campano, S.G., Porto Fett, A.C. 2022. Inactivation of Listeria monocytogenes and Shiga toxin-producing Escherichia coli in "soupie", a homemade soppressata. Food Protection Trends. 42(1):48–57.

Interpretive Summary: Soupie is a homemade soppressata common to the coal towns of northeastern Pennsylvania. Based on longstanding traditions, most soupie recipes use locally-sourced pork and a handful of non-meat ingredients that are ground, mixed, and then (hand) stuffed into beef middle natural casings before being fermented, flattened, dried, and then stored under oil for extended periods. What’s missing, however, are data on the overall safety and quality attributes of soupie, including its chemical composition and the presence and levels of bacterial pathogens and their potential ability to persist and proliferate in soupie. Therefore, we prepared soupie using a generic recipe and make protocol and purposefully inoculated it with cells of Shiga toxin-producing E. coli or illness-causing strains of Listeria monocytogenes. In general, our data confirmed that fermentation and drying reduced the levels of both pathogens by about 100 cells per gram. Following storage under sunflower oil or under vacuum in contact with sunflower oil for up to 6 months at ambient temperature it was possible to lower pathogen levels by a total of almost 1 million cells per gram. These data establish that soupie, as prepared and stored herein, is a shelf-stable, specialty/ethnic, fermented dry-cured sausage.

Technical Abstract: The viability of cells of Listeria monocytogenes or Shiga toxin-producing Escherichia coli (STEC) were monitored in “soupie”, a homemade soppressata. Coarse-ground fresh ham was mixed with non-meat ingredients, a starter culture (ca. 6.0 log CFU/g), and one pathogen cocktail (ca. 6.5 log CFU/g). The batter was then mixed before being fine ground, stuffed, and fermented at 26.7°C and ca. 90% RH for ca. 48 h to ca. pH 5.3. Next, chubs were dried at 15.6°C and ca. 86.5% RH for ca. 5 days, flattened under weights over three days, and then dried for an additional 21 days at 4°C and 72.5% RH. After drying, half the chubs were vacuum sealed individually in bags along with 8 mL of sunflower oil and the other half were submerged in sunflower oil (ca. 1.5 L) within covered plastic containers; all chubs were stored for 6 months at 20°C. Fermentation and drying delivered a ca. 1.2 log CFU/g reduction in levels of both pathogens. Thereafter, regardless of storage conditions, a ca. 5.0 log CFU/g reduction for both pathogens was observed within one and four months of storage at 20°C for STEC and L. monocytogenes, respectively. Although L. monocytogenes required more time (P < 0.05) to achieve a 5-log CFU/g reduction than STEC in soupie, there were no differences (P > 0.05) in viability of L. monocytogenes versus STEC after four months of storage and/or in viability of either pathogen related to whether chubs were stored vacuum-packaged with oil or submerged in oil. These data establish that soupie, as prepared and stored herein, is a shelf-stable, specialty/ethnic, fermented dry-cured sausage.