the efficacy of preservation methods to reduce the level of viruses is subdivided into methods: 1....
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Inactivation of food borne viruses by preservation methods
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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.
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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.
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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.
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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 .
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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.
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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.
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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 .
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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.
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Food preservation methods to establish microbial inactivation:
1. Heating2. High hydrostatic pressure processing3. Irradiation
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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.
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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.
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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
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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
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Reference: L. Baert et al. (2009). The efficacy of
preservation methods to inactivate foodborne viruses. International Journal of Food Microbiology 131 :83–94.