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Almost all foods consumed need some form of cooking and processing for making it fit for consumption. The nutrients we receive from the meals depend largely on the extent of cooking practices used. Some of the nutrients are lost during cooking. Cooking also has its benefits like:
- It increases palatability
- It makes food easily digestible
- Pathogenic micro-organisms are destroyed, thus safe.
- The appearance of food improves
Food prepared in large quantities in institutional kitchens or food processing plants is more prone to loss of nutrients if adequate care is not taken to preserve its nutrients. In the initial stages of cooking the soaking of food in water leads to leaching of vitamins and minerals. These losses can be minimized by washing the uncut fruits and vegetables and not soaking them in water.
Various effects seen on the nutrients are primarily because of the HEAT, ALKALI, and ACID.
Effect Of Heat On The Nutrients
- In carbohydrates, cooking has a beneficial effect as it leads to gelatinization of starch and caramelization of sugar which gives color and flavor to food.
- Proteins get denatured thus access to enzymes and digestibility increases.
- Moist heating of pulses improves protein quality.
- Chemical reactions take place when oil is continuously heated. Reactions like hydrolysis, oxidation, and polymerization of the oil. Oil becomes dark and foamy, such an oil should not be used for consumption
- Blanching inactivates certain enzymes that lead to undesirable browning.
- Heat labile vitamins are lost.
- Fat-soluble vitamins are lost during fat frying if a product is not coated properly.
Effect Of Alkali On Nutrients
- Alkali is used during cooking and processing to soften vegetables. Pinch of sodium bicarbonate added to green vegetables helps in brightening the green color.
- B complex vitamins and Vit.C are destroyed in an alkaline medium.
- Excessive cooking in the alkaline medium not only destroys vitamins but makes the texture mushy and gives a soapy taste to the product.
Effect Of Acid On Nutrients
- An acidic medium while cooking helps to preserve water-soluble vitamins and retards enzymatic browning of certain fruits and vegetables.
- Vegetables and pulses take a longer time to cook in an acidic medium as acids precipitate pectin and harden vegetables.
- Vegetables lose their color, so to overcome this allow the volatile acids to escape first, hence greens should be cooked without lid for the first few minutes.
Guidelines For Preserving Nutrients
- Wash vegetables, fruits and rice in just a sufficient amount of water. It is advisable either to cook in a minimum amount of water or to use the cooking water in soups and gravies.
- Cutting vegetables to small pieces and exposing them to air before cooking leads to loss of vitamins particularly vitamin C. Thus it is advisable to cut large pieces and cook for a shorter period.
- The 3 R’s of cooking to conserve nutrients are:
- Reduce the amount of water
- Reduce the length of the cooking period
- Reduce the amount of surface area exposed
- Oil heated repeatedly should not be consumed as repeated heating during frying leads to the production of toxic substances due to pre-oxidation and rancidity.