Inactivation of food borne viruses by preservation methods

The efficacy of preservation methods to reduce the level of viruses is subdivided into methods:

1. To hinder microbial growth during storage

2. To inactivate micro-organisms

3. To reduce the microbial load by decontamination

processes.

In Europe, viral agents were responsible for 10.2% of the

food borne outbreaks.

)of the67%It was estimated that each year in the US ( food borne acute gastroenteritis cases are attributed to viruses.

(NoV( ,)HAV ,), rotavirus astrovirus and enteric adenoviruses were depicted as food borne

associated viruses.

Fresh products and shelfish can be considered as high risk foods .

At the (post) - harvest stage, infected food handlers

not respecting hygienic regulations.

The latter risk is associated with any food item handledmanually which is not intended to be heated

beforeconsumption.

In contrast to most microbiological agents, viruses can not grow on food .

Cultivable viral strains and representative surrogateviruses used to estimate the the behavior of their related human infecting strains .

Food preservation methods to establish microbial growth inhibitione :

Chilling, freezing, acidification, reduced water activity

modified atmosphere packaging.

• FreezingGenerally, freezing will not ensure an adequate reduction of the viral load on foods except on strawberries and raspberries, probably due to the acid environment.

Chilling

Longer survival of HAV was noted on lettuce due to the size ,

also a faster decline on fennel and carrots.It may be related to polyphenols that could form complexes with viruses rendering non-infectious units.Ham protected the virus better against dryness. Contrary to fresh produce, ham is rich in proteins and fats.

Acidification Such low pH levels(pH 1 to 3.5) are not prevailing in foods due to unacceptable sensorial quality. Enteric viruses such as NoV and HAV will probably survive acidification or

fermentation of foods as preservation method .

Modified atmosphere packaging (MAP ) can inhibit spoilage causing bacterial and

- fungal micro organisms to extend the shelf life of foods .

Reduced water activity

Reduced water activity and the accompanying low relative humidity of food slows down the growth rate of bacteria and other micro-organisms.Virus strain and type of surface factors

contributingto inactivation rates at specific RH

conditions.

Food preservation methods to establish microbial inactivation:

1. Heating2. High hydrostatic pressure processing3. Irradiation

Heat treatment

There is a resistant to disinfection because of the formation of aggregates .

The mechanism of inactivation above 65°C might be caused by large irreversible structural changes presumably due to extensive protein unfolding.

High hydrostatic pressure processing

In contrast to heat, HPP does not disrupt covalent -bonds thus maintaining the primary structure ofproteins.A disadvantage of HPP is that viral strains could develop resistance to this technology.

Irradiation

UV inactivation of micro-organisms is probably due to the absorption of UV by nucleic acids.The combined effect of ( size/type )of the virion and nucleic acids are thought to be factors determining .resistance/sensitivity of viruses towards UV

Food preservation methods to reduce the microbial load:

Decontamination of fresh produce 1. Washing with water2. Chlorination 3. The use of other chemical agents Purification of live bivalve shellfish

Reference: L. Baert et al. (2009). The efficacy of

preservation methods to inactivate foodborne viruses. International Journal of Food Microbiology 131 :83–94.