PATHOGEN PERSISTENCE AND PROCESSING OPTIMIZATION FOR ELIMINATION IN FOODS
Location: Food Safety and Intervention Technologies
Title: Effect of storage temperature and cooking time on viability of Listeria monocytogenes and Escherichia coli 0157:H7 in/on goetta
Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 2013
Publication Date: April 23, 2013
Citation: Porto Fett, A.C., Pierre, J., Shoyer, B.A., Luchansky, J.B. 2013. Effect of storage temperature and cooking time on viability of Listeria monocytogenes and Escherichia coli 0157:H7 in/on goetta. Journal of Food Safety. Vol. 33,p.128-136.
Interpretive Summary: Goetta is a partially-cooked loaf of meat/mush that is widely popular in the greater Cincinnati area of the United States, where it is especially enjoyed as a breakfast item. There have been no reported recalls or illnesses associated with goetta, presumably because relatively little of this product is produced/consumed and presumably because goetta has limited geographic distribution/availability. However, based on its composition and anticipated refrigerated shelf life of 2 to 4 months, as well as based on consumer handling, storing, and cooking practices, we deemed it necessary to determine if goetta provides a favorable environment for persistence/growth of two of the most prevalent and deadly foodborne pathogens, namely Listeria monocytogenes and Escherichia coli O157:H7. Although these pathogens may be eliminated during cooking/processing, if present, they can be re-introduced onto the surface of goetta if the finished product is exposed to the food processing environment prior to packaging and/or if after being opened the finished product is mishandled or left uncovered at retail or within a consumers refrigerator. Our data confirmed that L. monocytogenes grew very well at 4 deg C, increasing from about 10 to about 100 million cells over the 3-month storage period. E. coli O157:H7 did not grow at 4 deg C as expected. However, when goetta was inoculated and then stored at 12 deg C to simulate the temperature abuse likely to be encountered in a consumers refrigerator, both L. monocytogenes and E. coli O157:H7 increased in numbers from about 10 to about 100 million cells within 1 month. The good news is that cooking for the recommended time of 6 minutes per side on an electric skillet at the recommended cooking temperature of 176 deg C destroyed more than 100,000 cells of both of these pathogens. Thus, our data highlight the importance of proper storage and cooking of specialty/ethnic products such as goetta to extend shelf life and ensure wholesomeness.
We evaluated the viability of Listeria monocytogenes and Escherichia coli O157:H7 on goetta, a sausage-like meat product, both during extended refrigerated storage and following cooking. For growth experiments, goetta was hand sliced (ca. 1.25 cm thick x 6 cm diameter; ca. 33 g each) and inoculated on both the top and bottom surface with ca. 1.4 log CFU/g of a five-strain cocktail of L. monocytogenes or E. coli O157:H7. The inoculated slices were placed into nylon-polyethylene bags, vacuum-sealed, and then stored at 4 or 12 deg C for up to 90 days. For cooking experiments, goetta was inoculated with ca. 7.0 log CFU/g of the five-strain cocktails of L. monocytogenes or E. coli O157:H7 and placed into a kitchen mixer for 2 minutes to distribute the inoculum before patties (ca. 2.5 cm x 6 cm diameter; 75 g each) were formed using aluminum molds. The patties were then cooked for 2 to 6 min per side on an electric skillet maintained at 176.7 deg C. For growth studies, at 4 deg C, L. monocytogenes numbers increased from ca. 1.4 log CFU/g to ca. 8.4 log CFU/g over 90 days, whereas E. coli O157:H7 numbers remained relatively unchanged. At 12 deg C, L. monocytogenes and E. coli O157:H7 numbers increased from ca. 1.4 log CFU/g to ca. 9.0 log CFU/g over 28 days. After cooking for 2 to 6 minutes per side, a 0.7- to 6.6-log CFU/g reduction of L. monocytogenes and E. coli O157:H7 levels was observed. Although goetta supported the growth/survival of L. monocytogenes and E. coli O157:H7 during refrigerated storage, a higher than 5-log reduction of both pathogens was achieved by cooking the product for at least 5 min per side at the manufacturer recommended internal temperature of 73.8 deg C.