Title: Thermal inactivation kinetics of a three-strain composite of Salmonella Enteritidis and Oranienberg in commercially-acquired liquid whole egg and 10% salted liquid egg yolk Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 13, 2010
Publication Date: August 1, 2010
Citation: Gurtler,J.,Marks,H.,Jones,D.,Rivera,R. 2010. Thermal inactivation kinetics of a three strain composite of salmonella enteritidis and oranienberg in commercially-acquired liquid whole egg and 10% salted liquid egg yolk [abstract]. International Association for Food Protection (IAFP) 97th Annual Meeting. Anaheim,CA. p.1. Technical Abstract: Introduction: Liquid egg pasteurization requirements are based on time/temperature combinations in the Code of Federal Regulations, Title 9, Ch. III, Sec. 590.570 from data acquired prior to 1970. These guidelines are being reevaluated in light of recent risk assessments, which take into account changes in industrial practices. Purpose: The goal of this study was to determine the inactivation kinetics of thermally-resistant Salmonella in commercially-acquired liquid whole egg (LWE) and 10% salted liquid egg yolk (LEY). Methods: Heat-resistant Salmonella Enteritidis and Oranienburg were grown in Tryptic Soy broth at 37 C, concentrated by centrifugation, and resuspended in peptone water. Each inoculum was added to liquid egg products and mixed, resulting in final populations of ca. 8.4 log CFU/ml. Inoculated egg was injected into sterile glass capillary tubes, flame-sealed and heated in a water bath at 56, 58, 60, 62, or 64 C for LWE and 62.2, 63.3, 65, 67 or 69 C for salted LEY. Contents were surface plated, incubated at 37 C for 24 h, and colonies were enumerated. Results: Survival curves were not log-linear (log levels versus time). After initial periods, for respective products, survival curves became linear. Asymptotic decimal reduction values were calculated from survivor curves with a minimum inactivation of 5 log CFU/ml at each temperature. The asymptotic thermal D-values for LWE were 5.77, 1.64, 0.41, 0.11, and 0.047 min at 56, 58, 60, 62 and 64 C, respectively. Asymptotic D-values for 10% salted LEY were 7.35, 4.42, 2.33, 1.15, and 0.46 min at 62.2, 63.3, 65, 67 and 69 C, respectively. Thermal Z-values were 3.72 and 5.80 C for LWE and 10% salted LEY, respectively. A model that predicts lethality for given times and temperatures was developed. Significance: This model will assist the USDA, FSIS in issuing pasteurization performance standards and provide industry guidance for designing pasteurization processes that will ensure safe product.