Quantification of the Relative Effects of Temperature, pH, and Water Activity on Inactivation of Escherichia coli in Fermented Meat by Meta-Analysis

Abstract

Outbreaks of Escherichia coli infections linked to fermented meats have prompted much research into the kinetics of E. coli inactivation during fermented meat manufacture. A meta-analysis of data from 44 independent studies was undertaken that allowed the relative influences of pH, water activity (a w ), and temperature on E. coli survival during fermented meat processing to be investigated. Data were reevaluated to determine rates of inactivation, providing 484 rate data points with various pH (2.8 to 6.14), a w (0.75 to 0.986), and temperature (؊20 to 66°C) values, product formulations, and E. coli strains and serotypes. When the data were presented as an Arrhenius model, temperature (0 to 47°C) accounted for 61% of the variance in the ln(inactivation rate) data. In contrast, the pH or a w measured accounted for less than 8% of variability in the data, and the effects of other pH-and a w -based variables (i.e., total decrease and rates of reduction of those factors) were largely dependent on the temperature of the process. These findings indicate that although temperatures typically used in fermented meat manufacture are not lethal to E. coli per se, when other factors prevent E. coli growth (e.g., low pH and a w ), the rate of inactivation of E. coli is dominated by temperature. In contrast, inactivation rates at temperatures above ϳ50°C were characterized by smaller z values than those at 0 to 47°C, suggesting that the mechanisms of inactivation are different in these temperature ranges. The Arrhenius model developed can be used to improve product safety by quantifying the effects of changes in temperature and/or time on E. coli inactivation during fermented meat manufacture.Fermented meats encompass a diverse range of product styles in which raw, ground meat is preserved by the processes of fermentation and drying (or maturation). These products are typically manufactured without a bactericidal heat treatment, and instead, inhibition of growth and inactivation of contaminating pathogens rely upon the collective effects of acid pH, reduced water activity (a w ), and the presence of lactic acid and, potentially, curing salts (nitrate and/or nitrite) and spices. However, pathogenic Escherichia coli can contaminate and survive in fermented meat products at levels sufficient to cause serious illness in consumers, as evidenced by numerous outbreaks of E. coli infections epidemiologically linked to uncooked fermented meat products (8,9,54,64). Knowledge of the kinetics of nonthermal inactivation of E. coli, and the factors affecting it, is important to be able to optimize the safety of fermented meat processes.Several research groups have conducted studies on the survival of pathogenic E. coli during the processing of specific fermented meat products (4,6,14,16,23,25). In some cases, the effects of alternative ingredients or processing parameters have also been determined (12,21,24,30). Such investigations have allowed the lethality of a specific fermented meat process to be determined and the microbiological safe...

Health and Safety Considerations of Fermented Sausages

“…The study indicated that temperature (fermentation, maturation, and storage) accounted for 61% of the variability in the data while pH and accounted for less than 8% [225]. Similarly, in a meta-analysis including 13 studies on inactivation of L. monocytogenes in fermented sausages, temperature explained 60% of the data variability while pH and explained only a small part [226].…”

“…Increased inactivation of relevant pathogens, including VTEC, L. monocytogenes, and Salmonella, with increasing temperatures has been shown in several studies [102,103,222,[225][226][227]. For effective inactivation of pathogens it is crucial to obtain conditions preventing pathogen growth (low pH, ), but once these conditions have been reached, it is the factors of time and temperature that most dramatically improve the microbial safety of the product.…”

“…These models have limitations as they primarily focus on the static effect of , NaNO 2 , pH, and temperature. The MLA model considers dynamic changes, however only those related to temperature in the sausage environment during production [225,286]. A simpler version of the MLA model calculates the reduction of E. coli as a function of temperature and time during fermentation and maturation, available at http://www.foodsafetycentre.com.au/fermenter.php.…”

Meta-analysis of the incidence of foodborne pathogens in Portuguese meats and their products

“…Yet, with meta-analysis, it is also possible to explain differences in the study outcomes by coding study characteristics, such as: research design features, data collection procedures, type of samples or even year (Hox & De Leeuw, 2003). In the past few years, meta-analysis has increasingly been applied in food safety (Den Besten & Zwietering, 2012;Gonzales Barron, Bergin, & Butler, 2008;Gonzales-Barron & Butler, 2011;Gonzales-Barron et al, 2013;Grieg et al, 2012;McQuestin, Shadbolt, & Ross, 2009;Sánchez, Dohoo, Christensen, & Rajic, 2007). In food safety research, meta-analysis may be conducted to address a broad range of research questions such as disease incidence, prevalence of microorganisms in foods, effect of interventions pre-and postharvest, risk ranking of pathogens and consumer practices, among others.…”

Predicting the Concentration of Verotoxin-Producing Escherichia coli Bacteria during Processing and Storage of Fermented Raw-Meat Sausages

“…coli O157:H7 has been modeled as a function of changes in the medium due to the metabolic activity of the starter culture and yeast during fermentation in olives (31) and as a function of pH and water activity (a w ) in soudjouk-style fermented sausages during the process of fermentation and drying (32). The publically available software THERM predicts the growth or lack of growth of E. coli O157:H7 and other pathogens as a function of the timetemperature history of raw-meat products (33); more specifically, tools implementing models to predict the inactivation of E. coli O157:H7 in raw meat (19) and in fermented meat products (34,35) are available from the Australia Food Safety Center of Excellence. However, predicting the response of VTEC throughout the range of conditions that comprise growth and no-growth environments characteristic to FRMS manufacturing and storage has not been approached yet.…”