Heat transfer
In order for food to be cooked, heat must be transferred from the heat source
Understanding the ways in which heat is transferred and the speed at which it is transferred helps the cook control the cooking process.
Heat is transferred in three ways: conduction, convection, and radiation.
CONDUCTION
- When heat moves directly from one item to something touching it. For example: from the top of the range to a soup pot placed on it, from the pot to the broth inside, and from the broth to the solid food items in it.
- When heat moves from one part of something to an adjacent part of the same item. For example: from the exterior of a roast to the interior, or from a sauté pan to its handle.
- Different materials conduct heat at different speeds. Heat moves rapidly through copper aluminum, more slowly in stainless steel, more slowly yet in glass and porcelain. Air is a very poor conductor of heat.
CONVECTION
- Convection occurs when heat is spread by the movement of air, steam, or liquid (including hot fat). There are two kinds of convection:
- Natural: Hot liquids and gases rise while cooler ones sink. Thus, in any oven, kettle of liquid, or deep-fat fryer a constant, natural circulation distributes heat.
- Mechanical.: In convection ovens and convection steamers, fans speed the circulation of heat. Thus, heat is transferred more quickly to the food, and the food cooks faster.
RADIATION
Radiation occurs when energy is transferred by waves from the source to the food. The waves them-selves are not actually heat energy but are changed into heat energy when they strike the food being cooked. (Light waves, radio waves, and X rays are examples of radiation not used for cooking.)
Two kinds of radiation are used in the kitchen:
- Infrared-In a broiler, an electric element or a ceramic element heated by a gas flame becomes so hot that it gives off infrared radiation, which cooks the food.
- Microwave-In microwave cooking, the radiation generated by the oven penetrates partway into the food, where it agitates the molecules of water. The friction this agitation causes creates heat, which cooks the food.
COOKING METHODS
- The culinary operation of subjecting food to the action of heat, which either makes it fit to eat or improves its flavour is known as cooking.
- Cooking brings about the following changes in a food –
- Chemical changes such as swelling or dissolving, coagulation, softening etc which makes food either edible or easier to digest; releasing of certain chemicals such as pectin, carotene,.
- It brings about changes to the external appearance of food making it more appetizing through browning of meats, the glazing of vegetables and caramelisation of sugar etc.
MOIST METHOD (MEDIUM OF LIQUID )
BOILING
- Boiling includes water to be boiled at 100 degree.
- Can be done in different forms of liquid like……..
- The amount of water used should be at least 4 to 5 times the volume of the vegetables
- The water should be boiling and usually the pot is covered with lid.
- There are different ways of boiling different type of vegetables and meat.
Blanching:
- To cook an item partially and briefly in boiling water or in hot fat. Usually a pre-proportion technique, as to loosen peels from vegetables, fruits, and nuts, to partially cook French fries or other food before service, to prepare for freezing, or to remove undesirable flavours.
- The term blanching is used for lightly cooking raw ingredients usually fruits and vegetables for varying amounts of time in boiling water with or without salt or vinegar. The ingredients are then refreshed in cold water a process known as shocking or refreshing.
STEAMING
- The food to be cooked is surrounded by steam from water, directly or indirectly
- Slow process of cooking.
- Can only use this method for food item that require less time to get cooked.
- The steam circulating around the food provides an even, moist environment that allows the food to retain most of its flavour and natural juices.
- En papillote/sous vide
POACHING
Eggs are poached at a temperature of 93-95ºC
SIMMERING
The temperature for simmering is between 90-95ºC.
STEWING
- method of cooking in a closed pan or a casserole using only a small quantity of liquid.
- The food should be more than half covered with the liquid and the food above this level is cooked by steam.
- As the liquid is not allowed to boil during cooking the process is a slow one and the food and the liquid are served together..
Braising is a combination of stewing and pot roasting where usually large joints of meat are cooked on a bed of vegetables with very little liquid in a covered pan or casserole
MEDIUM OF FATS AND OILS
The following methods are considered dry methods even though they use oil or fats. Although oil pours freely at room temperature, it functions differently than liquids, stocks, or water, and therefore not considered a liquid for cooking purposes.
SAUTÉING
This is a rapid method of cooking over high heat using a small amount of oil. The key to successful sautéing is to heat the pan before adding the oil. This ensures a caramelizing effect which sears the sides of the food. Sautéing literally means jumping, or to toss the food in the pan with very little oil
tir frying is associated with Asian cooking styles. A wok is the traditional tool for stir frying, because of its construction and shape. The wok concentrates heat in the bottom of the pan
Shallow frying/ pan fry
The object of pan frying is to produce a flavourful exterior with a crisp, brown crust, which acts a barrier to retain juices and flavour. In this method of cooking a substantial amount of oil is used.
DEEP FRYING
In this method of cooking foods are cooked by completely submerging it in hot oil or fat. Deep fried foods are almost always given a coating with flour, batter, or breading, which acts as a barrier between the fat and the food and also contributes flavour ands texture contrast.
Poeling is a technique most often associated with white meats and game birds, and is sometimes known as “butter roasting”. Meats are allowed to cook in their own juices in a covered vessel on a bed of aromatic vegetables known as Matignon.
Poeling is always done with butter and poeled items have a less pronounced colour than roasted items.
DRY METHOD OF COOKING
Dry heat simply means that no liquid is added to the food or the pan while cooking. Any addition of fat that might be added during cooking would be only to add flavour and not to act as a cooking medium.
GRILLING
Grilled foods are cooked by radiant heat from a source located below the food. A charred or smoky flavour resulting from the flaring of juices and fats that render out as the items cook
The term barbecuing is sometimes used to refer to grilled foods.
ROASTING
- This cooks food by surrounding them with hot dry air. Roasted foods are often basted during cooking.
- Spit Roasting
- Pot Roasting
- Oven roasting
- Tandoori
- Baking is cooking food by surrounding it with hot, dry air which is usually done in an oven.
- Temperature varies from 100ºC to 300ºC
- What is baking???
- Baking is the principle of cookery where food is subjected to the action of dry heat in an oven
- Some items need steam to improve volume and add crispness
(Pan of water can be placed in the oven to generate moisture and prevent the cake from drying out)
Oven baking
• Set the oven's thermostat to the desired temperature
depending on the food being cooked.
• Place the food on a greased sheet pan or rack, or use moulds without covers.
• Bake to the desired degree of doneness.
Some preparations require the oven heat to be increased or decreased after a certain period of time.
The oven, at a low temperature, may also be used to dry, rather than cook, certain foods, such as meringues
Quality may be affected….if
• ovens are not pre - heated
• oven doors are slammed during cooking
• temperature setting is incorrect
• the thermostatic controls are faulty
• there is a draught in the oven
• the oven doors are opened too early
• there is a power failure
• the cooking time is incorrect
BROILING
• Broiled foods are generally considered to be those cooked by a heat source located above the food.
• The salamander also known as the broiler is used to prepare broiled food which are often brushed with a marinade or butter to help them keep moist and to facilitate browning
PAN BROILING
Broiling must not be confused with “Pan Broiling” in which the food is cooked on top of a griddle or hot plate or in heavy cast-iron pan over intense heat. For example when broiling spices in a pan before grinding them.
SMOKING
• Cold Smoking: Here only smoke is present but no heat. You should be able to hold your hand above the wood chips and feel only a slight warmth. This method infuses a smoky flavour to the food and does not cook it completely.
• Hot Smoking: Some of the wood chips have a red glow to them which conducts heat and helps the food to get cooked apart from even smoking them.
MICROWAVE COOKING
• Micro waves are electro magnetic waves like light, or radio waves or x-rays. Their wave length is similar to the ones used in radar’s, and they can penetrate materials that do not conduct electricity.
THE MAILLARD REACTION
• It is millard reactions that produce the delicious aroma of fried, roasted and baked foods.
• is a chemical conjunction between the amino acids and the sugars present in the meats.
• This millard reaction can take place at a much lower temperature than is needed to caramelize sugar.
Comments
Post a Comment