NUTRIENTS LOST DURING COOKING :

Nutrients can be lost from food by one of three different means

• Intentional losses such as those that occur when cereals are milled, vegetables are peeled or individual nutrients are extracted from raw materials;

• Inevitable processing losses that result from blanching, sterilizing, cooking and drying foods;

• Accidental losses or avoidable losses due to inefficient processing or storage systems.

LOSS OF NUTRIENTS :

Vitamin A is found in foods like spinach, methi, carrots etc. Vitamin A dissolves easily in fats and oils. So, when food is fried in oil, vitamin A comes out from the food and goes into oil.

Vitamin B

 Vitamin B being water soluble, goes out of the rice and washes away with the water. After washing rice, it is soaked in water. Some more vitamin B goes out from the rice into the water during this process. Next, rice is boiled in water.  A lot of water used to cook rice and the extra water thrown away contains some dissolved vitamin B. Cooking soda also destroys vitamin B.

Vitamin C

 Vitamin C is an important nutrient which is easily destroyed by cooking. During cutting of vegetables and fruits some vitamin C is lost. Vitamin C is also lost when vegetables and fruits are washed after cutting and exposing cut vegetables to air for long periods before cooking. When the foods are cooked for a long time or the extra water thrown away contains some Vitamin C. Cooking soda also destroys vitamin C. Therefore, cooking procedures that minimize the loss of vitamin C result in conserving all other nutrients.

Proteins

 All proteins present in the foods coagulate by heat. Cooking results in softening of proteins in foods such as egg, fish, and meat, becomes water is bound in the process of coagulation. If the coagulated protein is further heated, it loses moisture and becomes dry and rubbery. They also become difficult to digest.

Oils and Fats

 When food containing fat are heated, the fat has the tendency to separate from the food. Oils and fats are used as a cooking medium. Some fat is absorbed during frying. When fats, ghee and oil, are heated for long period of time, its quality becomes poor.

Minerals

Minerals like sodium, potassium, etc. dissolve in water. Minerals get lost when food is first cut, then washed and the extra water in which they are boiled, is thrown away. Nutrients like vitamin B and C are lost when foods are boiled or soaked in water and the water is thrown away. Nutrients like vitamin A are lost when fats are used for cooking foods.

Loss of nutrients in vegetables begins from preparation onward and is greater during the cooking process.

1. When fruits and vegetables are peeled the vitamins present under the skin may be lost.
2. Nutrients are also lost when the edible leaves of carrot, beetroot and outer layer of cabbage are discarded.
3. Vitamin B complex and Vitamin C are water soluble and are lost when the water in which vegetables are cooked is discarded. Sodium, potassium and chlorine are also lost when cooking water is discarded.
4. Vitamin C is lost by oxidation due to exposure of air.
5. During dehydration ascorbic acid and carotene are lost.
6. Addition of soda results in heavy loss of B – Vitamins during cooking.

BROWNING :

When fruits and vegetables such as apple, banana, potato and brinjal are cut, there is a development of brown colour on the surface due to action of enzymes. This is known as enzymatic browning. When the tissue is injured or cut and the cut surface is exposed to air, phenol oxidase enzymes are released at the surface. These acts with the polyphenols present in the fruits and oxidises them to orthoquinones, which gives the brown colour to cut tissues.

Browning can be prevented by the following methods

1. Inactivation of polyphenol oxidase by applying heat.
2. Elimination of oxygen by vacuum packing.
3. Change of pH to prevent enzyme action.
4. Dipping of fruits and vegetables in brine and sugar solutions.
5. Use of antioxidants such as ascorbic acid to retard oxidation.