Food Science and Technology Department
Inactivation of Escherichia coli O157:H7 and Shiga Toxin Producing E. coli (STEC) Throughout Beef Summer Sausage Production and the use of High Pressure Processing as an Alternative Intervention to Thermal Processing
Date of this Version
Oliver, E.L., 2015
Escherichia coli O157:H7 and six additional serogroups of Shiga Toxin-producing E. coli (STEC-7) have been implicated in foodborne illness outbreaks related to fermented sausage products and are considered adulterants by the USDA-FSIS. The objective of this study was to evaluate high pressure processing (HPP) as an alternative to thermal treatment to reduce STEC-7 meeting the USDA-FSIS performance standards (5.0-log reduction). A rifampicin-resistant, non-pathogenic E. coli (surrogate) cocktail, was used in manufacturing testing. Sausages were fermented at ~42.2°C, slowly increased to 54.4°C internal temperature, cold showered, and chilled for 6 hours. Sampling occurred post-fermentation (PF; pH 5.0), internal temperature 48.9°C (I-48.9°C), 54.4°C (I-54.4°C), and post chilling (PC) for high fat (HF-17%) and low fat (LF-8%) sausage. Samples were HPP treated at 586 MPa for 1 sec, 1, 2, 3, 4 and 5 mins. Reductions of 1.2, 1.3, 3.1 and 4.2 log CFU/g were achieved at PF, I-48.9°C, I-54.4°C and PC, respectively. HPP resulted in additional reductions of 3.2 and >3.4 log CFU/g, at 1 and 2 mins, respectively (PC, LF). HPP (1s) of LF summer sausage that was heated to I-54.4°C (no hold), resulted in >6.6 log CFU/g reduction. Additionally, HPP was evaluated with three E. coli species cocktails which were inoculated onto pre-processed sausage including E. coli surrogates, E. coli O157:H7, and STEC. Cocktails were evaluated for HPP treatment at 586 MPa at 1s, 2, 4, and 6 mins. Reductions of 3.5, 5.0, 5.3, and 5.3 log CFU/g (STEC-cocktail) and 3.4, 5.2, 5.2, and 5.3 log CFU/g (O157:H7-cocktail) were obtained in LF sausage after 1 sec, 2, 4, and 6 mins. Surrogate reductions in LF sausage of 4.3 and ≥5.5 log CFU/g were obtained after 1 second and 2 minutes. HPP can be utilized as an alternative non-thermal lethality treatment in beef summer sausage to meet USDA-FSIS performance standards for E. coli O157:H7 and STEC.
Advisors: Bing Wang and Harshavardhan Thippareddi
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Food Science and Technology, Under the Supervision of Professors Bing Wang and Harshavardhan Thippareddi. Lincoln, Nebraska : December, 2015
Copyright (c) 2015 Eric Layne Oliver