Saturday, April 21, 2018

Influence of Cooking on Nutrients

All the foodstuffs we eat, except fruit and vegetable salads, require some sort of cooking or processing as they cannot be consumed in raw form.  Cooking is a culinary art form that makes the foodstuffs more palatable.  Along with that, cooking also makes the food easily digestible.  However, eating nutritious foods improves your health and energy levels.  But, the way food is cooked has a significant effect on the amount of nutrients in it.  Cooking influences the nutrients in the food items and some of them results in destruction.  Nutrients loss can be induced by several factors such as temperature, cooking time, and cooking method.

Proteins, fats, vitamins, and minerals are an essential part of our diet and nutrition.  On the other hand, carbohydrate, however, is not essential but is important for our body.  So, let’s see what happens to them when they undergo the cooking process.

Influences of Cooking on Protein:

On cooking, proteins in food items become hard and coagulate meaning they become firm.  You must have noticed the changes that occur when frying an egg.  The liquid turns solid on heating.  Isn’t it?  Yes, that process is known as coagulation.  Nonetheless, milk protein is unlike any other protein; this is an exceptional case because it does not coagulate.

Proteins are not lost as easily as vitamins and minerals during cooking, but it shrinks and hardens on overcooking, and this makes them indigestible, thus it is important to cook proteins to the right extent.  Overly heated food also affects the nutritive values of proteins.  Overcooking foodstuffs that contain protein can destroy heat-sensitive amino acids, for example, lysine; or make the protein more resistant to digestive enzymes.

Some pulses such as Bengal gram and soybean contain certain substances that inhibit the protein digestion of these foods by the enzyme trypsin (present in our intestines).  During the process of cooking, these trypsin inhibitors are destroyed.  Therefore, it becomes important not to consume these foods raw.  In fact, in several foodstuffs, the digestibility of protein improves as a result of moderate heating as in everyday cooking.

Influences of Cooking on Carbohydrate:

Carbohydrates are not essential but are important nutrients.  They come in a complex (starches and fibers) and in simple (sugars) forms.  When carbohydrates in food items are cooked, there are possibly two changes that occur i.e. gelatinization and caramelization.

Gelatinization is a process when the starch granules in foods absorb water and swell.  This process tends to thicken the soups, curries, stews to which refined flour (maida) paste is added.  It also helps in making chapattis/rotis or in the toasting of bread.  When you add certain carbohydrate food items like flour to liquids, the heat gelatinizes the carbohydrates.  Gelatinization takes place in all the starch-containing food items.

Sugar completely behaves differently.  When table sugar is heated, it forms a syrup and on further cooking, the syrup thickens and changes its color.  This is due to a process called caramelization.  The brown, thick liquid formed is known as caramel which is used in various preparations, for example, cakes and custard.  Normal cooking causes little loss of carbohydrates.

Influences of Cooking on Fats and Oils:

Our bodies need small amounts of 'good fat' to function and to be healthy.  Our usual cooking practices do not affect fats and oils in a substantial way, similarly to carbohydrates, and they are easily available to the body.

Fats and oils both are lipids.  Fats that are solid at room temperature are called as fats whereas fats which are liquids at room temperature are referred to as oils.  The temperature plays a vital role.  One should make sure not to heat fats and oils beyond its smoking point (a smoking/smoke point is the temperature at which fat/oils starts to burn and degrade) and should avoid repeated re-heating of fats because fats get broken down to form certain harmful substances when they are used repeatedly for frying.

Influences of Cooking on Vitamins and Minerals:

Vitamin and mineral loss can also be induced by various factors.  Some vitamins are fairly heat-stable, while others are heat-labile.  The factors other than heat that can destroy (some) vitamins are solubility in water, solubility in fat, exposure to air i.e oxidation, alkaline solutions, exposure to light (UV), storage losses, etc.

The water-soluble vitamins and minerals which are vitamin c, b complex vitamins (thiamine, riboflavin, niacin, biotin, folic acid etc), sodium, potassium, and chloride will be substantially lost if the liquid/water which is used for soaking, washing, and cooking is drained away.  So, throwing away the excessive cooking water also means throwing away the nutrients.  Hence, it is important to use the minimum amount of water or to utilize the liquid used for cooking.

Steaming, pressure cooking, boiling roots, and tubes with their skins limit cooking losses.  This secures the nutrients.  Cutting and peeling affect the amount of losses.  Cooking does not reduce the amounts of most of the minerals in food items which includes calcium, magnesium, sodium, copper, iron, zinc, phosphorus, iodine, manganese, chromium, and selenium.

    Related Post:  Enhancing The Nutritional Value Of Foods     

There are some vitamins which are heat labile.  These are vitamin c, thiamine, vitamin B 12, and folate, they are easily destroyed on excess heating.  The vitamin C is easily oxidized on exposure to air.  Vitamin A is also prone to oxidization.  These oxidized forms are of no use to the body.  Therefore, one should make sure not to peel vegetables or fruits much before use and should not cut them into small sized pieces because each piece will come in contact with air, get oxidized therefore destroying the vitamins.

Many people add sodium bicarbonate (baking soda) when cooking pulses.  You must be aware that adding soda to the pot fasten cooking process, making cooking easier, but do you know that it also knocks out the thiamine and riboflavin?  Yes, this is absolutely true that thiamine and riboflavin are easily destroyed in the presence of soda which is alkaline.  On the other hand, an acidic medium (for e.g. tomatoes, tamarind) preserves vitamins.

On a different note, fat-soluble vitamins are a class apart.  They are not influenced to any great amount by cooking in water.  Although, during roasting or shallow frying vitamin A is lost in significant amounts.  In deep frying cooking time is short and losses tend to be less.

You can preserve vitamins in foods by utilizing your foods when they are fresh, using steaming in preference to boiling, and by avoiding excessively long cooking times.

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