Food Science and Technology Department


Date of this Version

Fall 12-3-2015


Oliver, E.L., 2015


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


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