P1-150 Modeling Growth/No Growth Boundaries of Escherichia coli O157:H7 on Polyethylene Cutting Boards

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Joo-Yeon Lee, Korea Livestock Products HACCP Accreditation Service, Kyunggi, South Korea
Hee-Jin Suk, Korea Livestock Products HACCP Accreditation Service, Kyunggi, South Korea
Heeyoung Lee, Sookmyung Women's University, Seoul, South Korea
Soomin Lee, Sookmyung Women's University, Seoul, South Korea
Yohan Yoon, Sookmyung Women's University, Seoul, South Korea
Introduction:  Pathogens on cutting boards can be transferred to meat surface, and E. coli O157:H7 is considered as one of the major pathogenic bacteria in meat processing.

Purpose:  This study described a kinetic behavior of E. coliO 157:H7 and developed probabilistic model to calculate growth probabilities of the pathogen on cutting boards.

Methods:  E. coli O157:H7 (4 log CFU/cm2) was inoculated on polyethylene coupons (3 × 5 cm). The inoculated coupons were stored at 13, 15, 20, 25, 28, 30, 33 and 35 °C for 12 h, and E. coli O157:H7 cell counts were enumerated on McConkeyII with sorbitol agar every 2 h. Kinetic parameters (max: growth rate (log CFU/cm2/h), LPD: lag phase duration (h), and Nmax: upper asymptote (log CFU/cm2) were calculated with the modified Gompertz equation. The 0.5-log CFU/cm2 was used as a threshold to determine growth or no growth for 56 combinations (8 temperatures, 7 sampling times). The growth response data were analyzed with the logistic regression analysis to produce growth/no growth interfaces at 0.1, 0.5, and 0.9 of probabilities. The model performance was then validated with observed data.

Results:  Obvious growth of E. coli O157:H7 on coupons were not observed during storage at 12, 15, 20 and even at 25 °C for 12 h, but cell counts of the pathogen increased (< 0.05) at 28, 30, 33 and 35 °C with 4.31-7.20 h of LPD, 0.42-2.06 log CFU/cm2/h of max, and 5.7-7.1 log CFU/cm2 of Nmax, depending on temperatures. Growth/no growth boundaries of E. coli O157:H7 were produced at 0.1, 0.5 and 0.9 of probabilities with acceptable performance (concordance: 99.3 %, discordance: 0.6 %). In addition, validation for the developed model was acceptable.

Significance:  These results should be useful in determining working temperature and time not to allow E. coli O157:H7 growth on cutting boards.