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All foods have an ‘expiry date’

Written by Anusuya Suresh |Updated : March 25, 2015 12:54 PM IST

Food spoilt You must have noticed that cooked food which is not used up within a day or two shows typical changes in smell, appearance and taste. Dal takes on a thin layer of slime and begins to stink, rice turns yellow and gives off a peculiar smell, chapaatis show the appearance of a black fungus like growth all these are signs of food spoilage. Like homemade food, readymade foods also spoil, but the process is slowed down for long enough (by the use of certain preservatives) to allow shops to stock and sell the item.

Expiry Date for Foods

Identifying spoiled food is easy for food cooked at home most of us rely on our sense of smell and sight to know when food has gone bad. But what when food is inside a carton or other packaging material that renders it difficult to see and smell? You need to rely on the expiry date.

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When you buy food articles, you probably look at the price label; do you also look for the expiry date? Generally mentioned as 'Use by' or 'Use Before' or 'Best Before', these dates are an indication of the duration for which the food is of good quality in terms of taste and flavour. The term 'Expiry date' refers to the nutritional value and safety if you choose to consume food that is past its expiry date, you run the risk of exposing your body to food that has been spoilt.

How Does Food Spoil?

Food generally spoils because of two reasons first, it interacts with air and there is a reaction called oxidation that changes its chemical composition, causing it to degrade; equally important, bacterial present in the air enter the food and grow, causing it to diminish in quality.In some cases, such as milk for example, microorganisms are already present in food and if these are not killed by a process of sterilization, they will grow and multiply, causing the food to spoil.

Fruits and vegetables contain enzymes that cause chemical changes with time; when these foods are not consumed within a particular time, they spoil.

All Spoiled Food is not Hazardous

If you drink a little milk or eat a mouthful or two of pulao before you realize it is spoilt, you are not likely to suffer from food poisoning. Of course, if you consume a larger quantity, you do run a risk of a mild stomach upset. But food poisoning is a much more severe condition that occurs when the food is contaminated by bacteria that are dangerous called pathogenic bacteria such as E.coli or Salmonella. And here is the irony these pathogenic bacteria do not produce any change in colour, taste, smell or appearance like the innocuous organisms that are generally associated with food spoilage!

How Expiry Dates Help

When manufacturers pack perishable foods, they add certain preservatives to prevent bacteria present in it from growing at their normal rate. Foods such as meat and fish or even milk and curd need to be stored under refrigeration; this is because bacteria do not grow very fast under cold conditions and therefore, the food lasts longer than it would have done at room temperature. However, despite these precautions, even such readymade food will spoil after some time when bacterial growth reaches a particular level. The expiry date you see mentioned on product labels is arrived at after calculating the time food takes to spoil. If you consume food that is past its expiry date, it will have certainly reduced in quality due to spoilage setting in.

Tips to Prevent Food Spoilage and Wastage

Store them at a low temperature: When it comes to preventing food spoilage, the most important factor is temperature. Keeping food cold or frozen is the best way to reduce the growth rate of bacteria.

Thaw only the amount you need: But remember that when you thaw food, the bacteria get warmed up and start multiplying much faster. So, if you have excess food stored in the refrigerator, when you take it out and heat it up, it is best to use it at once without again pushing leftovers back into the fridge. If you anticipate that you won't be using the entire amount, retain the larger stock in the refrigerator and only thaw a small portion that you intend to use.

Keep the water content low: Bacteria thrive on moisture and if you manage to keep the water content low, it is possible to slow down spoilage of food. Substances like salt and sugar are capable of osmosis a process that draws moisture out from bacteria; the dehydrated bacteria do not survive. So now you know how homemade pickles and jams keep for months together even without the addition of preservatives!

Cook only for your present meal: Bacteria thrive at neutral pH; so food that is high in acid or alkaline content does not spoil very fast. Most natural foods such as fruits and vegetables are highly acidic or alkaline but the process of cooking causes the pH to slide to neutral, giving the bacteria the condition necessary for rapid growth. The lesson don't cook food you don't intend to eat immediately.

Don't store all fruits together: Certain fruits such as bananas and apples release a gas called ethylene as they age; too much of this gas can cause food to spoil faster. Keep these fruits away from other fruits and vegetables and they will stay fresh for longer.

Store in air-tight containers: Air and moisture are two factors that accelerate spoilage; keeping food in completely dry and air-tight containers keeps it unspoiled for longer.

Give up on hoarding: Often, especially when shopping at supermarkets, we tend to get carried away with discount offers on larger packs of food. But before you drop that huge pack into your shopping basket, take a look at the expiry date the discount may be a result of the pack reaching the end of its safe period. Think of whether you will be able to consume it within that time before buying.

Read more about causes, symptoms, diagnosis and treatment of food poisoning.

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