Nature always teaches us different lessons through its actions. Anything that happens in this universe makes us wiser and compels us to think on other related and unseen dimensions of these happenings. The ongoing COVID 19 crisis too has stimulated us to think. While interacting with my friends, relatives, students and other acquaintances during current lockdown, I realized that a common member of the society needs to have some basic understanding about disease causing viruses, their transmission and control. A significant quantum of information appeared in the columns of newspapers or got aired through electronic media which indeed has been useful. Being involved in teaching of the science of foods, I also got tempted to get engaged with readers and share my views regarding food borne viruses. Any food borne disease causing microbe , which is known as pathogen in medical terminology, has to cross certain barriers before getting established in the body and causing the disease. Many pathogens find way into our body through food, beverages, water or air. The first three carriers go through the digestive tract and the air moves through respiratory tract. Chewing or mastication is the first barrier that any food borne pathogen is required to cross as the food is subjected to a variety of physical actions in the mouth. The pathogens are also subjected to mildly unfavourable chemical environment in the mouth due to presence of saliva containing enzymes. The second barrier, more harsh and unfavourable, is the extreme acidic condition of the stomach. It is ordinarily very difficult for most of the pathogenic cells to overcome this barrier. As per the presently available knowledge, corona virus cannot withstand the high acidic conditions of the stomach. However, recent reports on presence of the virus in the faecal samples of some patients may suggest its resistance to stomach acids. But the safe passage of the virus through the gastrointestinal tract may not be of any pathological significance as the virus cannot find its receptors in this tract Nature has, however , given some pathogens the ability to form protective coverings around their cells to overcome harsh conditions like extremes of temperature and acidity. Spores of pathogenic bacteria or encapsulated cells are the examples wherein pathogens can overcome acidic conditions of stomach. Viruses, being among the extremely simple creatures of nature, are devoid of such encapsulations that can protect them from stomach acids. The protein coat and the envelope provides some protection to viruses but these protections cannot be compared with capsules of bacterial pathogens. Enteric viruses are considered to be resistant to adverse conditions , thus cause gastrointestinal disorders.
Another important aspect of pathogenic contamination of foods is the adherence of bacteria or viruses to the surfaces of food or its packaging or containers. Bacterial cells get attached to the surfaces of fruits and vegetables either through their specialized structures meant for the purpose or by producing adhesive or sticky materials. Viruses are devoid of such structures and do not produce any sticky materials but remain attached to the surfaces by some electrostatic forces. The attachment of viruses to food and other surfaces depends on surface properties of viruses and the electrochemical environment offered by the surface. Removal of viruses from the surfaces of fruits and vegetables does not involve harsh treatments. Washing of vegetables and fruits in clean running can remove most of the contaminating pathogens. The subsequent heat treatment during their cooking can completely destroy the pathogenic microbes. It has been noticed during current COVID crisis that consumers keep fruits and vegetables outside their homes or in garages for some time to get rid of virus or inactivate it. Such practices may reduce their nutritive value and freshness to a significant extent. It is, therefore, advisable to subject fruits and vegetables to hot water treatments like sprinkling or dipping to remove the virus ,if any, before we refrigerate or store them. The treatment should be just to dislodge and remove the contaminating organisms as prolonged heat treatments may reduce quality and storage life. Hot water treatment will ensure removal as well as inactivation of virus. Outbreak of some diseases in the past as a result of consumption of contaminated fruits and vegetables underlines the safety and precautionary measures to be adopted in food supply chain which starts from producers field. Fruits are borne by their mother plants in different manner; some are borne aerially like apple, pear, orange, banana etc., whereas others like strawberry, melons, root vegetables like radish are in close proximity to soil in which we cultivate them. There is greater probability of contamination of the latter category of produce with soil borne pathogens. The magnitude of the problem is higher if such soils are irrigated with untreated sewage waters or applied with organic manures as such waters and manures are the sources of many pathogens including the viruses which originate from the intestine. A two pronged strategy which includes proper treatment of sewage waters and organic manures to be used for crops whose produce is consumed raw and proper preparation of these products can effectively minimize the chances of contamination. Root vegetables like carrot have depressions or invaginations on their surfaces which harbour pathogens along with soil in them. Such invaginations should be properly cleaned during preparation of vegetables to be served as salad or consumed raw. Consumption of raw meat as is prevalent in some African countries can be another potential reason for outbreak of food borne diseases. Some important outbreaks of food borne viral diseases of recent past include that occurred in EU in 2008 due to consumption of crustaceans, shell fish and associated products. Consumption of contaminated berry mixes and strawberries resulted in another notable outbreak of viral disease due to presence of hepatitis A virus in 2013. Norovirus and hepatitis virus have been the major concerns in foods so far. The coronavirus is not believed to enter the body through food. However measures like good hygiene practices in homes as well as commercial processing plants, restriction of infected workers and good farm practices can go a long way in prevention of food borne diseases.
Farooq Masoodi is Head Dept. of Food Science & Technology, University of Kashmir