Cooking Methods (Benefits and Drawbacks)

∴ Definition of cooking Cooking is the application of heat to food in order to make it more delicious, improve its digestibility, and make it safer. Cooking not only improves the taste, smell, and appearance of food but can also increase its digestibility. The act of cooking, by killing fungi, yeasts, and bacteria that are either pathogenic or cause spoilage, improves the hygienic condition and the keeping quality of the food. To ensure that food is free of microbial contamination, it is essential that at the end of cooking, the central part of all foods consumed hot reach a minimum temperature of 75 degrees Celsius (steam rising from the surface of the food indicates that the central part has reached this temperature).

∴ Methods of heat transfer Food is a relatively good heat conductor, and in traditional cooking methods, food is heated from the surface and the heat is then transferred into the food. In general, heat is transferred from the heat source to the surface of the food using intermediate media such as water, steam, air, or oil.

∴ General methods of cooking food a/ Cooking with moist heat b/ Cooking with dry heat c/ Cooking with oil (frying)

a/ Cooking with moist heat In the moist-heat method, water is heated until it boils. The food is either placed directly in this water or placed in the steam coming off this boiling water so that it cooks. Cooking using moist heat is itself divided into three categories: 1/ Boiling 2/ Cooking with water (simmering) 3/ Steaming

1/ Boiling The surface of the food is covered with sufficient water and heated until the water boils. For cooking different foods, we use different amounts of water. For example, to cook vegetables such as spinach or other leafy green vegetables we use very low heat and small amounts of water, while to cook legumes such as lentils, beans, etc. we need large amounts of water. The water needed to cook green beans, peas, etc. is of a moderate amount between the two cooking methods mentioned above. In this cooking method, the following points should be observed: Before cooking, the food should be washed well. Use a sufficient amount of water. It is better to first bring the water to a boil and then add the food. For cooking, use a pot or container whose lid closes well so that the steam produced cannot escape; in this way the food cooks faster. Do not heat the food more than necessary. Prolonged heating causes the loss of color, texture, taste, and nutritional value. The water used to cook food contains nutrients that are soluble in water; use this water in other dishes and do not throw it away. The smaller the size of the food during cooking (i.e., the more it is chopped or cut), the greater the loss of nutrients in it will be. Therefore, as far as possible, do not chop vegetables too finely when cooking (and if possible, cook them whole and do not peel them).

2/ Cooking with water (simmering) In this method, the food is cooked in water for a longer time, but the heat is below boiling temperature and much less water is used; as soon as it comes to a boil, the heat is lowered and the food is allowed to cook for a longer time. This method is suitable for cooking tougher foods such as lentils, meat, and dried vegetables. The low heat in this method prevents the destruction of nutrients by excessive heat.

∴ Pressure cookers In this method, the food cooks quickly in less time under the high pressure produced by steam. The cooking time can reduce the energy consumed for cooking by up to 40 percent. Because increased pressure also raises the boiling point of water, the cooking temperature is therefore above 100 degrees Celsius.

• If foods, especially vegetables, are placed directly into boiling water rather than placed in cold water and then heated, fewer nutrients are lost. • Using slow cookers to boil or cook vegetables and rice cookers to cook rice helps preserve their nutrients. • Preparing rice as kateh preserves more of its nutrients. We are used to letting the food we cook "settle in," as the saying goes, but we do not realize the damage done during this process to the nutrients that we expect to reach our body by eating the food. For example, the vegetables we use in preparing borani or aash are rich in folic acid and vitamin B6, but they are destroyed and lost as a result of cooking at high heat for a long time.

3/ Steaming This is one of the healthiest methods of cooking food, in which moist heat (the steam produced by boiling water) is used to cook the food. Since the contact between the food and the water in this method is less than in boiling, the loss of nutrients is also less.

b/ Cooking using dry heat In the dry-heat cooking method, a higher temperature is used compared with the moist method, and to the same degree, a greater loss of nutrients occurs. Grilling and oven-roasting are the most common methods of cooking food using dry heat. In the grilling method, food is exposed to heat either directly (such as grilling over charcoal or a direct flame) or indirectly (such as grilling in a frying pan).

• Grilling food directly over fire or charcoal in a way that causes it to char is associated with the production of the most carcinogenic compounds. • Methods in which heat is applied to the food from above or alongside and the food is not in direct contact with the fire are associated with fewer harms. • Grilling in ridged frying pans and marinating food in lemon juice and aromatic herbs before grilling reduces the production of harmful compounds. In the oven-roasting method, an oven is used to cook the food. Cooking food this way is one of the healthiest methods, and many dishes and even various types of kuku and cutlets can be prepared this way.

c/ Cooking with oil (frying) Frying food is one of the traditional methods of cooking food that is best avoided as much as possible. The heat that reaches the oil during the frying of food causes the production of carcinogenic compounds called "peroxide" and "acrolein." The higher the frying temperature, the greater the amount of peroxide will be. The foods most vulnerable to the frying process are starchy foods. That is, foods such as French fries, sambuseh, falafel, and various types of potato kuku. ∴ To reduce the harms caused by frying food, pay attention to the following points: • Before frying food, heat the oil until it becomes a little hot. At this heat, a protective layer quickly forms on the surface of the food. On this basis, the oil does not pass into the food, and the food is cooked and fried only by indirect heat and the thermal conduction from this protective layer. • Avoid overcrowding food in the oil. In this case, the oil temperature drops and the oil penetrates into the food before the protective layer forms, and the food becomes greasy. • Do not salt the food before frying. Salt lowers the smoke point of the oil and causes the oil to break down and oxidize sooner. • Fry frozen vegetables while they are still frozen so that their absorption of oil is minimized. • Because of the possibility of forming harmful compounds in the oil, do not introduce a spoon coated with onion and tomato paste, or food, into the main oil container, and keep the oil in a closed container. • Use frying oil to fry food only once. When the oil's color darkens slightly or it foams during frying, the frying oil should be replaced. • For frying, use special frying oils, and use other liquid vegetable oils for cooking, sautéing, and oven-roasting. Use the minimum amount of frying oil.

Sources: 1/ www.environmentalhealth.ir 2/ fdo.mui.ac.ir, Food and Drug Deputy 3/ The collection of occupational health regulations in the petrochemical industry