Thermal Inactivation of Salmonella Agona in Low–Water Activity Foods: Predictive Models for the Combined Effect of Temperature, Water Activity, and Food Component

Abstract

Salmonella can survive in low-moisture, high-protein, and high-fat foods for several years. Despite nationwide outbreaks and recalls due to the presence of Salmonella in low-moisture foods, information on thermal inactivation of Salmonella in these products is limited. This project evaluated the impact of water activity (a), temperature, and food composition on thermal inactivation of Salmonella enterica serovar Agona in defined high-protein and high-fat model food matrices. Each matrix was inoculated with Salmonella Agona and adjusted to obtain a target a, ranging from 0.50 to 0.98. Samples were packed into aluminum test cells and heated (52 to 90°C) under isothermal conditions. Survival of Salmonella Agona was detected on tryptic soy agar with 0.6% yeast extract. Complex influences by food composition, a, and temperature resulted in significantly different ( P < 0.05) thermal resistance of Salmonella for the conditions tested. It was estimated that the same point temperatures at which the D-values of the two matrices at each a (0.63, 0.73, 0.81, and 0.90) were identical were 79.48, 71.28, 69.62, and 38.42°C, respectively. Above these temperatures, the D-values in high-protein matrices were larger than the D-values in high-fat matrices at each a. Below these temperatures, the inverse relationship was observed. A correlation between temperature and a existed on the basis of the level of fat or protein in the food, showing that these compositional factors must be accounted for when predicating thermal inactivation of Salmonella in foods.

Influence of low water activity on the thermal resistance of Salmonella Enteritidis PT30 and Enterococcus faecium as its surrogate in egg powders

“…The obtained D 80 ℃ -values for this mixture at each a w level selected were 25.43 ± 0.15, 12.45 ± 0.33, and 6.05 ± 0.10 min, respectively, which are similar to the D 80 ℃ -values obtained for yolk and white egg powders. Similar thermal resistances of Salmonella have been observed in foods products with a high-carbohydrate content (wheat flour) and products with a high-fat content (soybean oil) (Jin et al., 2018). Rachon et al.…”

“…The obtained D 80 C -values for this mixture at each a w level selected were 25.43 AE 0.15, 12.45 AE 0.33, and 6.05 AE 0.10 min, respectively, which are similar to the D 80 C -values obtained for yolk and white egg powders. Similar thermal resistances of Salmonella have been observed in foods products with a high-carbohydrate content (wheat flour) and products with a highfat content (soybean oil) (Jin et al, 2018). Rachon et al (2016) observed that at 80 C the inactivations rates for Salmonella in a high protein product (meat powder) are higher compared to the rates obtained for high-carbohydrate products (confectionary products), while at higher temperatures (<100 C) the inactivation rate was slightly higher for high-carbohydrate product, indicating a protective effect of sugars.…”

Isolation of Salmonella Typhimurium, Listeria monocytogenes and coagulase-positive Staphylococcus from salami sold at street fairs in Porto Alegre, Brazil

“…Although the sample units sent for a w analysis were not the same subjected to microbiological investigation, the similar results obtained from different salami units suggested that there might have been an inherent problem with shorter drying times for brand A. Although Salmonella has been shown to survive in low-moisture food (JIN et al, 2018), a w values around 0.96 seem to be needed for its growth, and a w values < 0.94 inhibit its growth (JAY et al, 2005). In this regard, a reduction of ripening time was identified as the main risk factor in a S. Typhimurium outbreak associated with salami consumption in Northern Italy (PONTELLO et al, 1998).…”

Evaluation of the Thermal Inactivation of a Salmonella Serotype Oranienburg Strain During Cocoa Roasting at Conditions Relevant to the Fine Chocolate Industry

“…These foods often have water activity (a w ) below 0.85, which prohibits the growth of most bacteria, including Salmonella (Young et al, 2015). However, exposure of Salmonella cells to sublethal stresses, such as desiccation, could potentially lead to its adaptation and increased resistance to subsequent heat treatment (Baird-Parker et al, 1970;Goepfert et al, 1970;Keller et al, 2012;Villa-Rojas et al, 2013;Jin et al, 2018). Microbial cells may survive in the desiccated state in low moisture foods during extended storage (Tamminga et al, 1976;Farakos et al, 2013;Beuchat et al, 2017) and resume active metabolism and growth upon returning to a favorable environment.…”

“…In addition to the previous exposure to stresses, the ability of individual microbial strains to resist heat treatment in low a w foods also varies (Izurieta and Komitopoulou, 2012;Alvarenga et al, 2018), which could potentially be to some extent attributed to microbial genetic background (Mercer et al, 2015(Mercer et al, , 2017. The effectiveness of thermal inactivation can be further influenced by the food composition, such as protein (Jin et al, 2018) and fat content (Kataoka et al, 2014;Li et al, 2014), which alter the food microenvironment and may provide a protective effect against heat treatment. When generating data to support food safety decision-making, it is therefore important to evaluate the thermal inactivation kinetics using relevant pathogen strains, at relevant conditions and food matrices that mimic real-life scenarios as closely as possible.…”