Influence of water activity on the heat resistance of Salmonella enterica in selected low-moisture foods

Bina Gautam; Byju N. Govindan; Michael Gӓnzle; M. S. Roopesh

doi:10.1016/j.ijfoodmicro.2020.108813

Influence of water activity on the heat resistance of Salmonella enterica in selected low-moisture foods

Bina Gautam, Byju N. Govindan, Michael Gӓnzle, M. S. Roopesh

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Abstract

Low-moisture foods (LMF with water activity, a_w < 0.85) including pet foods and black pepper powder have consistently been associated with foodborne disease caused by Salmonella enterica. Increased heat resistance and prolonged survival at low-moisture conditions, however, remain major challenges to achieve effective inactivation of Salmonella in low-moisture foods. At low water activity (a_w) conditions, heat resistance of Salmonella is greatly enhanced when compared to high a_w conditions. This study aimed to quantify the effect of a_w on the heat resistance of Salmonella enterica in pet food pellets and black pepper powder. Pet food pellets were inoculated with two strains of heat resistant S. enterica and black pepper powder was inoculated with a 5-strain cocktail of Salmonella. Both inoculated food samples were equilibrated at 0.33, 0.54, and 0.75 a_w in controlled humidity chambers. Inoculated pet food pellets and black pepper powder in closed aluminum cells were heat treated at specific temperatures for selected times. The results showed that the Weibull model fitted well the inactivation data. At a specific temperature, the rate of inactivation increased with the increase in the a_w from 0.33 to 0.75, and the 3-log reduction times decreased for Salmonella in both food samples with the increase in a_w. Water adsorption isotherms of pet food pellets and black pepper powder at initial and treatment temperatures were developed to understand the change in a_w during heat treatments. The change in a_w during heat treatment was dependent on the type of food matrix, which possibly influenced the thermal inactivation of Salmonella in pet food pellets and black pepper powder. The quantitative analysis of heat reduction of Salmonella with respect to a_w aids in selection of the appropriate initial a_w to develop effective heat treatment protocols for adequate reduction of Salmonella in pet foods and black pepper powder.

Original language	English (US)
Article number	108813
Journal	International Journal of Food Microbiology
Volume	334
DOIs	https://doi.org/10.1016/j.ijfoodmicro.2020.108813
State	Published - Dec 2 2020

Bibliographical note

Funding Information:
We acknowledge the research support from Alberta Livestock and Meat Agency and Alberta Agriculture and Forestry (Grant number: 2016R045R ) and the Natural Sciences and Engineering Research Council of Canada (Grant number RGPIN-2017-05051 ).

Publisher Copyright:
© 2020 Elsevier B.V.

Keywords

Black pepper powder
Heat treatment
Pet foods
Water activity
Water sorption isotherm
Weibull model

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title = "Influence of water activity on the heat resistance of Salmonella enterica in selected low-moisture foods",

abstract = "Low-moisture foods (LMF with water activity, aw < 0.85) including pet foods and black pepper powder have consistently been associated with foodborne disease caused by Salmonella enterica. Increased heat resistance and prolonged survival at low-moisture conditions, however, remain major challenges to achieve effective inactivation of Salmonella in low-moisture foods. At low water activity (aw) conditions, heat resistance of Salmonella is greatly enhanced when compared to high aw conditions. This study aimed to quantify the effect of aw on the heat resistance of Salmonella enterica in pet food pellets and black pepper powder. Pet food pellets were inoculated with two strains of heat resistant S. enterica and black pepper powder was inoculated with a 5-strain cocktail of Salmonella. Both inoculated food samples were equilibrated at 0.33, 0.54, and 0.75 aw in controlled humidity chambers. Inoculated pet food pellets and black pepper powder in closed aluminum cells were heat treated at specific temperatures for selected times. The results showed that the Weibull model fitted well the inactivation data. At a specific temperature, the rate of inactivation increased with the increase in the aw from 0.33 to 0.75, and the 3-log reduction times decreased for Salmonella in both food samples with the increase in aw. Water adsorption isotherms of pet food pellets and black pepper powder at initial and treatment temperatures were developed to understand the change in aw during heat treatments. The change in aw during heat treatment was dependent on the type of food matrix, which possibly influenced the thermal inactivation of Salmonella in pet food pellets and black pepper powder. The quantitative analysis of heat reduction of Salmonella with respect to aw aids in selection of the appropriate initial aw to develop effective heat treatment protocols for adequate reduction of Salmonella in pet foods and black pepper powder.",

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N1 - Funding Information: We acknowledge the research support from Alberta Livestock and Meat Agency and Alberta Agriculture and Forestry (Grant number: 2016R045R ) and the Natural Sciences and Engineering Research Council of Canada (Grant number RGPIN-2017-05051 ). Publisher Copyright: © 2020 Elsevier B.V.

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Influence of water activity on the heat resistance of Salmonella enterica in selected low-moisture foods

Abstract

Bibliographical note

Keywords

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