Effect of Cooking on Nutritive Value of Foods

Almost all foods consumed by man are subject to cooking, the exception being fruits and vegetables, which are consumed raw for salads, juices and chutneys. When one talks of nutritional content of foods, it should be related to cooked foods. However, cooking practices vary from on region to another. Hence, cooked food cannot be standardized. Cooking has both adverse and beneficial effects.

We will discuss the common cooking methods which are practiced in India, which include boiling, steaming, pressure cooking, frying, roasting and baking. The loss of nutrients on cooking depends on the temperature, duration of cooking and the nutrient.

Ordinary cooking causes the little loss of protein, fats and carbohydrates in cereal, pulses and meat. Some protein and a considerable amount of minerals may be lost due to leaching, if the food is cooked in water containing salt and the cooking water is discarded. This water may contain various minerals like Sodium, Potassium and Calcium.

Therefore, one should cook in as less water as possible or the water should be used in soups or gravies. Steaming, however, prevents losses due to leaching. Root vegetables, however, do not suffer much loss of nutrients since their outer skin prevents the leaching out of nutrients. That is why; the root vegetables should be cooked with their skin on and then peel that skin before using them in to various other preparations.

Cutting vegetables into small pieces and then exposing them to air can also leads to the loss of various nutrients specially vitamin C. Therefore, cut the vegetables in to larger size pieces and immediately put them in boiling water to cook. It would be much beneficial if you cook them for a short period of time.

Here i also want to discuss about the nutrients loss in rice as rice is the staple food in our country and it provides so many nutrients to human body. Significant amount of nutrients are lost due to preliminary washing of the rice. So, it is advised to wash the rice, only if necessary and that too with minimum water. This washing may remove about 40% of thiamine and nicotinic acid.

Secondly, boiling rice in excess amount of water and then discarding that extra water may also result in losing various vitamins and minerals. However, this loss is much less than the loss of nutrients through preliminary washing. Therefore, the rice should be cooked with just sufficient amount of water, so that all the water is absorbed. If you are using the parboiled rice then the loss of nutrients in both the cases is much less as when the rice is parboiled, the nutrients diffuses in to the grain and a protective gelatinised starch coating is formed on the grain, which prevents leaching.

More than the minerals, it is the vitamins, especially the water soluble B group vitamins, which show a greater loss during cooking. Vitamin A and carotene are not lost during wet cooking. Cooking in an acid media with tamarind and other acids has a protective effect against vitamins.

If the fat is repeatedly heated during frying, may contain toxic substances, due to oxidation and rancidity. It may be a desirable practice to use a minimum quantity of fat for frying and avoid using it over and over again.

On the other hand, cooking also has some beneficial effects. It improves the appearance and palatability of the food. Apart from that, cooking also destroys several harmful food-borne microorganisms. It also improves the digestibility of various foods, especially starch.

Cooking eggs helps in destroying Avidin, which is known to bind biotin and make it unavailable. Protein digestibility is also reduced by trypsin inhibitor. That is why; other protein sources like pulses and legumes should always be cooked, as heating or autoclaving the legumes helps destroy the trypsin inhibitor and improve the protein quality.

Thus, cooking has several advantages in improving the quality, digestibility and palatability of the food. At the same time, cooking also can reduce the vitamin and mineral content, but taking certain precautionary measures like cooking in limited water and in presence of acids, it can help preserve vitamins to a greater extent.

I hope this information will help you in choosing best cooking practices and techniques.

Be happy and stay healthy !!

Nainja