Thermal Inactivation of Foodborne Enteric Viruses and Their Viral Surrogates in Foods

Abstract

Foodborne viruses, in particular human norovirus and hepatitis A virus, are the most common causes of food-associated infections and foodborne illness outbreaks around the world. Since it is currently not possible to cultivate human noroviruses and the wild-type strain of hepatitis A virus in vitro, the use of a variety of viral surrogates is essential to determine appropriate thermal processing conditions to reduce the risk associated with their contamination of food. Therefore, the objectives of this review are to (i) present pertinent characteristics of enteric foodborne viruses and their viral surrogates, (ii) discuss the viral surrogates currently used in thermal inactivation studies and their significance and value, (iii) summarize available data on thermal inactivation kinetics of enteric viruses, (iv) discuss factors affecting the efficacy of thermal treatment, (v) discuss suggested mechanisms of thermal inactivation, and (vi) provide insights on foodborne enteric viruses and viral surrogates for future studies and industrial applications. The overall goal of this review is to contribute to the development of appropriate thermal processing protocols to ensure safe food for human consumption.

Thermal Inactivation Kinetics of Tulane Virus in Cell‐Culture Medium and Spinach

“…Traditionally, for the first‐order kinetic model, the change in number of survivors over time has been described using the following equation of a straight line (Bozkurt, D'Souza, & Davidson, ; ; , Bozkurt, Ye et al., ): where – k is slope (and D = –1/slope), N ( t ) is the number of survivors after an exposure/treatment time ( t ) in PFU/mL, and N 0 is initial target population (PFU/mL). The D ‐values for different temperatures were plotted on semilog coordinates, and the temperature change for a one log‐cycle change in D ‐values was calculated as the z ‐value as previously reported (Bozkurt, Ye et al., ).…”

“…Historically and traditionally, thermal inactivation has been most widely used to inactivate pathogens in food and for food preservation. Heat causes protein denaturation of viral capsids resulting in noninfectious viral subunits and single individual proteins (Bozkurt, D'Souza, & Davidson, ; Song et al., ). Above 60 °C, after the inactivation/destruction of host‐cell recognition and binding receptors, an alteration of the tertiary protein structure is reported to occur that can facilitate the access of thermal energy to the nucleic acids (Ausar, Foubert, Hudson, Vedvick, & Middaugh, ; Bertrand et al., ).…”

“…In industrial settings and research laboratories, in order to understand the heat inactivation kinetics of microorganisms, D ‐ and z ‐values are determined. The D ‐value is defined as the time at a given temperature necessary to reduce microbial populations present in a defined medium by 90% (or 1 log) and is indicative of the thermal resistance of a microorganism at a constant temperature (Bozkurt, D'Souza, & Davidson, , ). The z ‐value is defined as the change in temperature required to increase or decrease the D ‐value by 90% and is indicative of the temperature dependence of microbial inactivation (Bozkurt, D'Souza, & Davidson, ).…”

The Effect of Heat on the Physicochemical Properties of Bacteriophage MS2

“…MS2 phage was used as a model because of its similar size (&22-29 nm), the presence of a positive-sense RNA genome, and an overall structure of the capsid close to enteric pathogenic viruses (Bae and Schwab 2008;Boudaud et al 2012;Bozkurt et al 2015;Deboosere et al 2012;Shirasaki et al 2009;Sidhu and Toze 2009;Valegård et al 1990). This phage is non-pathogenic for humans and easy to culture in laboratory.…”

Thermal Inactivation of Enteric Viruses and Bioaccumulation of Enteric Foodborne Viruses in Live Oysters (Crassostrea virginica)

“…Additionally, it has been shown that virus inactivation by thermal processing does not follow a linear inactivation model (firstorder kinetics), which assumes a linear logarithmic reduction of the quantity of the treated virus with time (45). A virus thermal inactivation curve usually shows shouldering and tailing at the beginning and end of the survival curve, respectively, limiting the ability to use decimal reduction times (D values) to establish the inactivation parameters.…”