During cooking, the natural forms of many foods are processed for human consumption. Many physical and chemical reactions occur during the processing or preparation of foods. Selection of the right cooking method to maximise the nutritional quality of your meal is the key to healthy eating. There is no perfect method of cooking that conserves all nutrients. This article helps you understand the effects of cooking on the nutrients in food and ways to retain its nutritional value.
Right or wrong?
Let's start with a comparison of two ways to cook a couple of vegetables:
1. Cooking cauliflower:
What's wrong: What do you do when you see a worm squiggling in your cauliflower? Boil the florets in water? Well, that’s certainly not the best way to do it because boiling kills the antioxidants such as vitamin C along with the worm. Microwaving also reduces cauliflower’s nutrient content.
What's right: Try steaming it instead. Steaming preserves the vitamin C and retains the crunchiness of the vegetable. To get rid of the worms, simply wash the florets in running water or water to which some salt has been added.
2. Cooking tomatoes:
What's wrong: Tomatoes contain lycopene that prevent heart disease. If you think that eating it raw or steamed is the best way to get its full benefit, you’re mistaken.
What's right: To get the maximum benefit out of the lycopene in tomatoes, chop them up and add them to your curries or rasam. You’ll love the tangy flavour and make the most of its nutrient content as well.
Does this make you wonder what's the right technique to employ in your kitchen so you can serve your child a healthy meal?
5 cooking tips to preserve nutrients
Recent studies have shown that there are several ways to enhance the availability of healthy nutrients through proper cooking techniques.
- Techniques like pasteurisation and canning involves cooking, so canned fruits, vegetables and pasteurised milk need not be cooked again, but can be reheated on the stovetop or in the microwave oven for shorter time.
- Wash all fresh fruits and vegetables with cool tap water and avoid soaking when you wash to prevent leaching in water.
- Reduce the number of times you rinse pulses and grains, such as rice, before cooking, as nutrients may wash down the drain.
Your cooking methods greatly influence the nutrient retention in foods.
Steaming is one of the best cooking methods for preserving nutrients, including water-soluble vitamins that are sensitive to heat and water. A study found that steaming broccoli, spinach and lettuce reduces their vitamin C content by only 9-15%.
How to: Steaming can be done in two ways – as dry steaming (double boiling) or waterless cooking (cooking food wrapped in an aluminium foil/plant leaves).
Common foods: Idli, dhokla, puttu, idiappam, appam, kozhukattai and custard.
2. Poaching and stewing
Poaching is a quick method of cooking using very less liquid at a temperature below the boiling point. Heat-sensitive nutrients can be conserved in this method due to less exposure to heat. However, water soluble nutrients may be leached into the liquid used for poaching.
Stewing is a gentle method of cooking using small quantities of liquid to cover only half the food. The food gets cooked by the steam generated. Loss of nutrients by leaching out the liquid does not take place in stewing.
How to: Use minimum amount of liquids while poaching and stewing.
Common foods: Poaching - Eggs, fish and fruits.
Stewing - Meats and vegetables.
3. Pressure cooking
Pressure cooking preserves the nutritional value of the foods. The high heat, intense pressure and shorter cooking times reduce vitamin and mineral losses occurring in other cooking methods.
How to: Pressure cooking for about 3 minutes improves the protein digestibility of legumes by reducing anti-nutrients considerably.
Common foods: Rice, dal, vegetables and meat.
Shorter cooking times and reduced exposure to heat are the keys to preserve the nutrients and flavours in microwaved foods.
Research states that microwaving is the best method for retaining the antioxidant activity in vegetables and mushrooms. About 20-30% of vitamin C in green vegetables is lost during microwaving, which is less than most cooking methods.
How to: Cover the vegetable while microwaving it to still further reduce loss of nutrients.
Common foods: Includes a variety of foods.
5. Use of fat as medium of cooking
When fat is used as medium of cooking, sautéing, stir-frying and shallow fat frying are the healthier ways to prepare foods, because cooking for a short time without water prevents loss of B and C vitamins. The addition of fat improves the absorption of fat-soluble vitamins and antioxidants.
How to: Be mindful of the fat/oil used in cooking. Oils when heated above their smoking point may turn rancid and harmful for consumption. Do not reuse oils. Fats and oils with lower smoking points, like butter and olive oil, are best suited for lower temperature cooking methods such as sautéing instead of frying.
- One study found that absorption of beta-carotene was 6.5 times greater in stir-fried carrots than in raw.
- In another study, lycopene (antioxidant) levels increased 80% more, when tomatoes were sautéed in olive oil rather than without.
- Research states that vitamin C concentrations of fried potatoes are as high as in raw potatoes and thiamine is well retained in fried potato products as well as in fried meat.
- Frying may also increase the amount of fibre in potatoes by converting the raw starch into resistant starch.
Why nutrients are lost while cooking
Cooking changes the nutritional content of food. According to the TNAU Agritech Portal, cooking causes an inevitable loss of nutrients from food.
Let’s consider the effect of cooking on some nutrients:
Vitamin C: This vitamin is found in plenty in fruits and vegetables. A University of Parma research reveals the effects of steaming, boiling and frying on vitamin C. When you steam your peas for 5 minutes, it results in a 32 per cent loss of vitamin C whereas 48 per cent is lost on boiling it and 87 per cent on frying. A study states that the loss of vitamin C was lesser during pressure cooking when compared to boiling.
Parent takeaway: Planning to serve your family peas as snack or starter the next time? Remember to steam/pressure cook them.
Folate: A B-vitamin, folate is the most essential nutrient for cell growth. It is on every pregnant woman’s list of must-have vitamins. Let’s look at the effect of cooking on this important vitamin. Spinach contains about 100 mcg of folate per half cup when cooked. Boiling it results in a 58 per cent loss of folate in just 10 minutes. Steaming it for even 5 minutes results in no loss of folate whereas frying results in a 50 per cent loss.
Parent takeaway: If steaming is the best way to cook spinach, go for it!
While we're talking about healthy ways to cook, let's look at more ways to prevent nutrient loss.
Potassium: Isn’t this the nutrient that’s good for the heart? That makes it all the more important to cook it right. Potatoes are rich in potassium. If you boil them in a pot of water, about 50 per cent of the nutrient is lost. More so, if you’ve cut the potato before boiling it. Also, most of the potassium is lost when the water in which they are cooked is discarded,
Parent takeaway: Steaming potatoes with the skin intact is the best way to retain potassium.
Proteins: Meat, eggs, beans and legumes contain a good deal of proteins. The quality of protein may be reduced due to denaturation (destruction) of certain amino acids during cooking (e.g., hardening of meat).
Parent takeaway: Cooking does not significantly impact the protein content in food.
Vitamin A, D and E and K: These are fat-soluble vitamins. When you cook them in a lot of oil, they leach (remove from food) the vitamins into the oil. Up to 60 per cent of B-vitamins are lost when meat or fish is simmered for over 30 minutes. If you thought this was bad, just 5 minutes of boiling meat sees a loss of 45 per cent of vitamin B-6. Β-carotene found in carrot is better retained in microwaving compared to pressure cooking.
Vitamin A, found in abundance in foods like spinach and carrots, dissolves easily in fats and oils. When you deep fry these foods in oil, the vitamin comes out from the vegetable and goes into oil. The carotenoids found in this vitamin are well-preserved on boiling these vegetables.
Parent takeaway: Carrots have a high concentration of antioxidants after boiling. Remember to use the water in which you boil the carrot or cabbage in your stew or soup.
Tip: Cooking for shorter time periods at lower temperatures with minimal liquid will help in retaining the nutritive value of foods.
Do you have any preferred method of cooking a particular food? Share it with us in the comments below.
Knowing the right method of cooking food to retain nutrients is a vital part of ensuring the healthy growth and development of your child. Flip through this ClipBook to know the essential nutrients you should give your 5-year-old.