Cooking makes food delicious, but also affects the nutrient value of the ingredients. While some methods of cooking, such as stir-frying, steaming, microwaving, roasting and sautéing, improve nutrient value, others, such as deep-frying, barbecuing, or pressure-cooking, may destroy them. The spinach in palak paneer or soup, for instance, has been cooked far too long to preserve any of the folic acid that the leafy vegetable would otherwise have provided the body with. Leafy greens need just 3 minutes of any kind of cooking to retain nutrients. On the other hand, the antioxidant lycopene in tomatoes and carrots becomes available to the body only after the vegetables have been cooked in some form. Rajma or kidney beans must be cooked to a soft consistency to make them digestible whereas moong dal sprouts are delicate and nutrients in them are destroyed if cooked on high heat.
Cooking is the process of preparing/combining and blending various foods and food groups, herbs and spices by adding heat to improve palatability and visual appeal. But for some food items too much heat can destroy their nutritional value. In fact even cooking with too much water can destroy the delicate vitamins and antioxidants that are present in certain foods. Also, cooking on high heat, such as barbecuing and grilling, can alter or denature the proteins in meats and eggs. Over-browned meats too are more susceptible to carcinogenic activity, which is why it is best to restrict the consumption of over-browned meat to just once in a while. For day-to-day cooking, it is better to cook meats just short of browning. Even the burnt crust on toasted starchy foods such as bread or naan makes them a lot less healthier.
For cooking to be nutritious, it has to be quick—the food should sizzle in the pan for the shortest possible time, with a minimal amount of its surface area directly in contact with heat. Waterless cooking, steaming and stir-frying are least destructive to nutrients.
How to preserve nutrients
• Use minimal water. Too much water leaches out vitamins and minerals from vegetables. If you must use water, then use a small amount of boiling water to cook in or pour over. This reduces overall cooking time and preserves nutrients.
• Quick cooking on a tava or griddle maintains the highest levels of antioxidants.
• Avoid pressure-cooking and over-boiling because the high water content and high heat lead to nutrient losses.
• It is best to stir-fry cauliflower and broccoli (and other cruciferous veggies). Boiling and microwaving these leads to nutrient losses.
• Green beans, beets and garlic are hardy. They can maintain their antioxidant levels with almost all forms of cooking.
• It is better to cook tomatoes, green beans, carrots and celery. Antioxidant levels in these increase on cooking.
• Cook foods in a preheated pan or boiling water to allow heat to deactivate destructive enzymes in foods.
• Remember that cutting food into smaller pieces destroys nutrition because it exposes more of the surface to heat.
• Using baking soda to preserve the colour of green vegetables can destroy the thiamin and Vitamin C content in them.
• Cooking potatoes with skins preserves the Vitamin C in them.
• Roasting meat for a long time destroys its thiamin content.
• Pre-heat food in a microwave oven before putting it into the pan or on a grill. This way you can reduce the time needed to heat up the food and reduce the harmful browning of food.
Madhuri Ruia is a nutritionist and Pilates expert. She runs InteGym in Mumbai, which advocates workouts with healthy diets.
Write to Madhuri at firstname.lastname@example.org