COOKING-PRINCIPLES, METHODS & ITS EFFECTS COOKING INTRODUCTION Most of the food products which we eat are cooked before consumption. Cooking makes the food tasty, attractive, colourful, easily digestable & also ass variety to texture. Cooking also kills many micro-organisms & make the food safe to be consumed. Several raw food have antinutritional factors which are destroyed by cooking. However, if proper care is not taken while cooking, several important nutrients rae destroyed. So, it is very important to employ proper method of cooking to avoid nutrient loss. Some methods employed before cooking 1. Peeling: It is a method of removing the outer firm skin before cooking or eating fruit or vegetable. Some of vegetables & fruits are eaten with the peel. 2. Chopping It involves cutting of fruits & vegetables. Food is cut into several sizes to create variety in the cooked food 3. Grinding & pounding In grinding, the food is reduced to very fine form like spices. Sometimes cereals are also ground to powder. Pounding is also like crushing food to reduce thickness for easier cooking. 4. Soaking Pulses & legumes are soaked for few hours before cooking to make cooking easier. 5. Sprouting or germinating This method is used for pulses, legumes & grains. This method not only add variety to food, but also increases the content of vitamin C & vitamin B complex in the food. Cooking methods Methods employed for cooking of food can be categorized under two heads: 1. Moist heat methods 2. Dry heat methods 3. Other methods COOKING METHODS Moist heat dry heat other methods Boiling roasting sautering Simmering grilling frying Pressure cooking toasting - deep frying Steaming baking - shallow frying Poaching Stewing Blanching Moist heat methods It is defined as those methods of cooking, in which water is used as medium for transferring heat for ccokingg. 1. Boiling It is a method in which water is boiled above 1000C. Several foods are cooked by this method e.g. rice, dal, potatoes etc 2. Simmering Simmering is the method of cooking, in which food is cooked below the boiling point i.e, about 850C of temperature. This method takes a long time to cook food. 3. Pressure cooking It is the method of cooking food by steam under pressure. In this, food is cooked above boiling temperature of 1000C. During pressure cooking heat generated is not allowed to escape 4. Steaming This is the method of cooking, in which food does not come in direct contact with food. The steam is generated by boiling water in pan & another pan which is placed in water, in which food is to be cooked is kept. 5. Poaching Poaching is a method of cooking comparatively smaller amount of liquid is used & food is cooked for longer tome at low temperature. Food is covered half with liquid & as soon it reaches boiling point, the heat is reduced for longer cooking. 6. Stewing In this method of cooking comparatively smaller amount of liquid is used & food is cooked for longer time at low temperature. Food is covered half with liquid & as soon it reaches boiling point, the heat is reduced for longer cooking 7. Blanching Blanching is a process, in which food is dipped in boiling water. The aim of this method is to inactivate the enzyme & to remove the peel easily, then the food is dipped in cold water. This method is used generally for tomatoes. Dry heat methods Dry heat methods are defines as those methods of cooking which donot apply water or moisture for cooking. 1. Roasting In this method, little oil is used for coating the food with fat.. the food is brought into direct contact with heat source & continuously stirred, until fully roasted E.g. Tandoori chicken, fish tikka 2. Grilling In grilling, food is placed on metal grill directly over the source of heat. This method is used for tender cuts of meat, poultry or fish. It makes the food crispy & brown 3. Toasting Toasting is similar to grilling. Eg. Bread toast 4. Baking It employs the principle of hot air circulating around the food, placed in closed chamber like oven. The heat action works in combination with steam generated from food. Baked food are crisp & brown from outside. But soft & spongy from inside E.g. Biscuits, cookies & cakes Some other methods of cooking 1. Sautéing This method employs use of minimum amount of oil & vegetables are stirred in the oil just to give little coating of oil & to cook it faster. 2. Frying It is defined as cooking food by immersing in oil. It is further of two type: a. Deep frying When food is completely immersed in hot oil, till it is golden brown & crispy. It is called deep frying. E;g: Samosa, purees, etc are cooked by this method b. Shallow frying In shallow frying food is partly dipped in oil. E.g. Prantha, besan chill, tikki Effects of heat on nutrients Heat put effect on digestibility of various nutrients. Carbohydrates Starch is most affected carbohydrate by heat. Starch grainabsorbs water, swell up & cellular walls get ruptured. The process is called gelatinization & starch is called gelatinized. While if water is not used for cooking, then dry heat converts starch into dextrin. This is responsible for brown colour of food & sweet taste of baked cereals. Proteins Proteins undergo coagulation on heating. Proteins coagulate at the temperature of 600C or above Fats Fat is not much affected by heat. But overheating & reheating brings about hydrolysis of fat. This leads to production of free fatty acid. Minerals Heating have little or negligible affect on minerals. But they are lost with water Vitamins All vitamins are affected differently by ccoking e.g. Vitamin C which is heat unstable & is destroyed by cooking, vitamin B complex especially thiamine, riboflavin vitamin K are destroyed in the pressure of NaHCO3 (soda bicarbonate) & also lost in water. Heat have little or negligible effect on vitamin A & D..