We all know that food is a potential source of infection. The moment we have a stomach upset we suspect it to be due to food. The contamination in food may be due to microorganism, microbial and non-microbial toxins, and worms or by added chemicals that are not natural to the food itself. Food can be contaminated at any point during its journey from the producer to the consumer. Therefore, careful handling is necessary at every stage. Food hygiene in the widest sense implies hygiene in production, handling, distribution, cooking and serving of all types of food.

1) Microorganisms:

Microbes, specifically bacteria, cause either food poisoning or food infection. You must have observed that food left at room temperature for long is spoiled; this is because microbes are omnipresent and food is the growth medium where they flourish. They multiply over a period of time and thus, are produced in large numbers. In their metabolic processes, toxic substances are secreted. Some of the toxins are heat-labile i.e. they become harmless if food is sufficiently heated. But many are heat-stable. That is why, intake of such food results in food poisoning. We can often judge and reject such foods by the look, texture or foul smell. But some infections, like botulism, for example, cannot be identified by appearance. It is common in tinned food, particularly in cold meats when due care is not taken in preservation. The botulism toxin, though fatal, is heat-labile.

Food infections:


On the other hand, are due to introduction of disease-causing bacteria in food by careless handling, cooking or serving. For instance, during coughing, the spray of aerosol introduces virus or bacteria in the food. These microbes do not multiply in food, instead they enter and multiply in the human body and cause severe illness. Even a few bacterial cells invading the body are enough to cause disease.

The symptoms of food-borne diseases in general are:

(i) Fever, (ii) Diarrhea, (iii) Vomiting and pain in abdomen, (iv) General weakness, and (v) Dehydration.

2) Parasites:


These are generally worms, which grow in the body. Actually, food gets contaminated by ova of worms that are released in the faces. Ova can get into food by unhygienic handling of food or by using still or infected water, that is a reservoir for infection. The ova hatch into worms in the body. For example, round worm disease. The female roundworm (Ascaris) produces over 200,000 eggs per day in the intestine of infected person which are passed to the soil in faces. These are hatched into larvae. Once larvae are consumed, they grow into tiny worms in the intestine.

3) Natural Toxins:

Many molds that grow on food also produce toxins, which are poisonous for man. For example, a field fungus Ergot infects food grains like bajra, wheat and rye during seed formation. Consumption of such infected grain results in ergotism which is characterized by acute episodes of nausea, repeated vomiting, giddiness and drowsiness. In chronic cases painful cramps in limbs and gangrene occur.

Another fungus Aspergillus flavors that infects groundnut grains, sweet potatoes and cotton seed and their cake, produces toxic substances known as aflatoxins. Among these aflatoxin – B is a potent carcinogen, producing liver cancer, which ranks high in incidence in our country. Fungal toxins are called mycotoxins. Sometimes, foodstuffs, especially grain, pulses and oil seeds are accidentally contaminated by poisonous seeds, which are hazardous to health. For example, mustard seeds are mixed up with seeds of poisonous plant Argemone mexicana, which causes dropsy. Millets similarly are contaminated with seeds of Crotalaria which contains a toxic alkaloid. This causes Hepatotoxic jaundice and Ascites. Khesari dal — Lathyrus sativus causes lathyrism, a nervous system disease, characterized by paralysis of lower limbs, especially in males.


Many animals, mostly marine animals, contain toxins. There are about 500 species offish that are known to be poisonous. Consumption of clams and mussel results at times in paralytic shellfish poisoning.

4) Chemicals in Food:

The practice of adding colors, flavors or preservative to food is not new. Presently, more than 3,000 synthetic and natural chemicals are being used for various purposes. Most of the foods available in the market contain some chemicals termed as food additives. These are defined as “non-nutritious” substances intentionally added to food, generally in small quantities to improve its appearance, flavor, texture or storage. Let us look at the different classes of food additives given in.

It must be pointed out that generally new food additives are introduced without adequate testing of their long-term physiological effects. In fact, testing of a chemical is a tedious, lengthy and very expensive process. It may sometimes require millions of rupees and many years of research. In India, generally, the new food additives are introduced from the West. Even when their ill effects on health are found and they are banned in the western countries, their use in our country continues.


Uncontrolled or indiscriminate use of increasing number of food additives may pose health hazards among consumers. Hence, food additives are subject to government regulation.

5) Metals:

Toxic metals such as mercury, lead, tin, zinc, arsenic and antimony may get into the body through food, water or while breathing in an environment containing dust from these metals. Regardless of their mode of entry, we will discuss their effect on health in this section.

You know about the mass poisoning in Japan in the 1950s, which resulted due to eating of fish taken from Minamata Bay where the water was polluted with methyl mercury. Practically all mercury in diet comes through consumption of fish poisoned by water containing mercury. The metal in the body kills cells and damages organs with which it comes in contact and thus impairs their functioning. Chronic exposure causes lesions in the mouth and skin and neurological problems. Inhalation of mercury vapors is meter dangerous than its ingestion.


The typical symptoms of poisoning by mercury vapors are: (i) irritability, (ii) excitability, (iii) loss of memory, (iv) insomnia, (v) tremor and (vi) gingivitis.

Another potent poison is lead, which gets into food by the use of water from lead pipes, packing of food in lead containers, using machines for processing or packing food and use of pesticide spray containing lead. People working in the factories using lead may encounter it by inhaling active lead dust. Lead affects brain, and in developing children leads to mental retardation, lowered IQ, and behavioral abnormalities. It retards the formation of hemoglobin and damages kidneys.

Cadmium is widely used in industry. After ingestion or inhalation, it is deposited in the kidney. Long exposure to cadmium results in brittle bones, damaged kidneys, testes and liver. The Itai-itai disease first reported from Japan was shown to be due to cadmium toxicity.

The metals that enter food from cheap cooking utensils are antimony, zinc and tin. Preserved food are stored in tin cans. Cautious use of such foods is very essential. To some extent we can identify contamination of metals by change in colour or metallic taste. You may have noticed that acidic foods change the appearance of the surface of a metallic container. Acids react with the metal or the container and form compounds, which are mixed with food. Finally, we must also point out that metals like iron, copper, magnesium, etc., that are essential in our body, can be utilized only in a specific chemical form and in a controlled amount, otherwise they may be harmful. For example, copper is necessary for the body but copper-contaminated foods are toxic.


Food Adulteration:

An adulterant is any ingredient which when present in food is injurious to health. This definition has been given by the Indian Prevention of Food Adulteration Act (PFA) enacted in 1954. The commonly adulterated foodstuffs are pulses, spices, coffee, tealeaves, edible oils, ghee, butter, flour, etc. Pulses are mixed with corresponding khesari pulse, roasted tamarind and date seeds are ground into coffee powder, exhausted tea leaves or colored saw dust are mixed into fresh tea, cheap seeds are mixed with black pepper, cumin, cardamom and edible oils are adulterated with non-edible oils. We have mentioned before that seeds of Argemone mexicana are poisonous and are accidentally mixed with mustard seeds. It is unfortunate that oil from these seeds is extracted and is used to adulterate coconut, seasame and groundnut oils. Often it is seen that the so-called fresh-shelled peas sold in the market are actually, dry peas soaked in water that are colored to give .them the look of fresh peas. The dangers of such adulterants go unchecked. In the following subsection, you will learn how you can assure the quality of a product available in the market.