August 20, 2014

The risks of food poisoning

Changing lifestyles in the modern hurly-burly world has occasioned an augmented demand for ready-to-eat foods, also called fast foods. A concomitant of this drastic change is the risk of bacterial food poisoning. How does food poisoning occur? Usually it takes an immense number of food-poisoning  bacteria to be present in food in order to cause sickness. Given the right conditions, however, bacteria can multiply very quickly.

food poisoning

These conditions include
Time: Time in ideal conditions, just 1 bacterium can multiply to 2,097,152 in the course of 7 hours.
Temperature: Food-poisoning bacteria grow prolifically in the temperature range 50C-600 C. This is termed the temperature danger zone.
Nutrients: Bacteria require their own source of food top grow and multiply.

Bacteria mainly prefer the types of foods called high risk foods (HRFs) such as dairy products. Pasteurized milk is free from this risk. So, only pasteurised milk should be taken or used to prepare other dairy dishes.

dairy products

In our homes curd is generally made by mixing a small amount of old curd into fresh , lukewarm milk; this provides an ideal culture medium for bacteria as it supplies nourishment as well as a favourable temperature.
Since the process is repeated daily, the bacteria present in the old sample are carried forward to the following day's curd and so on.

At times, raita is made out of this curd by mixing chopped vegetables into it. In this process, if the pH (acid, alkali balance) of curd increases above 5, harmful organisms may multiply on storage.

As regards ice-creams, although, undoubtedly, milk used in its preparation by reputed companies gets sterilised when it is boiled, contamination can take place when it is cooled and flavours and additives are added.

Dormant Bacteria
Bacteria introduced at this stage may not perish. When the milk is frozen, these become dormant whereafter they become active again when the temperature rises during transportation or while eating.

Regarding eggs, they may be contaminated with the faeces of birds that laid them, whether chicken or duck. Under certain conditions of temperature and humidity, the germs ca penetrate the shell. This is a common occurrence with ducks eggs, but these of course, are not much consumed.

Even rice which is eaten by a large number of people, both vegetarians and non-vegetarians, is a HRF. Spores of an important food-poisoning bacteria called as Bacillus cereus can contaminate rice and these spores are not killed by the cooking temperature. So when cooked rice is left at room temperature for a long time these spores multiply and even reheating cannot kill them. So it's best to consume cooked rice quickly or it can be stored in a fridge (after cooling it within 1 hour) and has to be consumed within a day after steaming it in a pressure cooker.

cooked rice
Cooked rice is a high risk food.

As sliced bread and confectionary are generally stored for long periods, in a warm environment, during sale in bakeries, during transport and while in storage in the house, they are quite likely to harbour harmful germs and accord a favourable medium for their multiplication. These also should therefore be stored always in fridges.

Cold sweets like barfi, gulab jamun, rasgullas and custards are also ideal media for the growth of bacteria. Flies can contaminate them during repeated handling, during preparation, and storage at atmospheric temperature.

Low Risk Foods
Low risk foods (LRFs) area: Jams, syrups, honey and so on. The high concentration of sugars in these dissolve in water to form concentrated solutions, leaving enough moisture for the growth of bacteria.
Salted mat, anchovies, olives, etc., are also LRFs for the reason cited above. Here the concentration of salt occurs.

Other LRFs are fatty foods, acid foods, dry foods like cereals and pulses. These grains if properly stored, do not support bacteria but once cooked, bacteria have access and multiply. So these should always be stored in the fridge.

Canned foods also come under the category of LRFs. If the can is bulging due to production of gas in the container, it is harmful. Otherwise, canned foods are quite safe.

But after these are opened , they should be treated only as fresh food. Use intensely acidic canned foods like tomato and apple products within 1-11/2 years. Other canned foods like meat, poultry, stews, pasta products, potatoes and peas can stand storage for even 2-3 years. But once opened, the products have to be consumed swiftly.

The reasons are not far to seek. When acidic foods are packed in metal cans, the acid dissolves the metal which is absorbed into the contents of the can, causing spoilage. The acid itself softens the preserved food causing deterioration.

Hard foods like meat, pasta and potatoes preserve better because during processing they can withstand the duration and temperature needed for total sterilization - 1210C, for 20 minutes at 15 pounds pf steam pressure.

But, succulent foods like tomatoes and apples, as also mangoes, cannot withstand such processing without change of their flavour and texture. So they are heated at a lower temperature, lesser pressure and longer time. Owing to incomplete sterilization, spoilage in such foods is more likely.

Thaw Completely
Ensure that you thaw completely the frozen foods prior to your cooking them as otherwise the ice crystals in the middle of the food block the temperature that reaches the centre at the time of cooking from being sufficiently high to eradicate the bacteria there. Then, the temperature also will be conducive for bacteria to multiply.

Always cook food at one time and not piecemeal because bacteria remain alive in partially cooked foods and upon cooling they multiply and survive all through subsequent partial cooking.
90% of food-borne illnesses that strike people, especially in summer, are preventable if the above precautions are taken.

If you think you have food poisoning, don't lose any time to report to the doctor. Retain any leftover food which you believe might have caused you to become ill for analysis in laboratories.

(Contributed by Priti R.)

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