BASIC FOOD SCIENCE AND COOKERY.
Food is a mixture of many different chemical components. The study of food science involves an understanding of the changes that occur on these components during food preparation. Study of food science also includes understanding the nutritive value of different foods and methods of preserving them during cooking.
The principle cereal crops are rice, wheat, maize, jowar, ragi and bajra.
Cereals are the main source of energy. Rice provides 345 calories and 6.8 grams of protein per 100 grams and wheat provides 341 calories and 12.1 grams of protein per 100 gms. Ragi is a rich source of calcium and iron. Wheat and ragi are rich in fibre. Whole grain cereals are an important source of B vitamins in our diet.
When starch granules are mixed with water and cooked the grains absorb water and swell. This process is known as gelatinisation.
If starch is subjected to dry heat, it is converted to dextrin, giving a brown colour. This is called dextrinisation.
Glutenin or glutelin and gliadin are proteins present in wheat. During the mixing of a dough the long strands of glutenin evidently becomes aligned in the direction of mixing and forms a film that envelopes the starch granules in the dough. In the presence of water and with mechanical agitation, the protein fraction forms a tough elastic complex called gluten, which is capable of retaining gases and by doing so, a leavened product is obtained. Due to its elastic property, the dough can be rolled to prepare chapathis or puris.
Pulses are edible fruits or seeds of pod bearing plants. The major pulses which are used are red gram dhal, bengal gram dhal, black gram dhal and green gram dhal.
Pulses contain 55 to 60% starch. Every 100 grams of pulses provide about 350 calories and 22 grams of protein. Pulses are excellent source of B complex vitamins particularly thiamine, folic acid and pantothenic acid. Soyabean provides 43 grams of protein per 100 grams. Whole grams are good sources of protein, B-vitamins and fibre.
Many pulses particularly whole grams, which have hard outer covering need soaking prior to cooking. Addition of sodium bicarbonate hastens the cooking process, but is not advisable because it destroys the B vitamins.
The term vegetable is used to refer to those plants or parts of plants that are served raw or cooked as a part of the main course of a meal.
Nutritionally they are classified into 3 groups,
Green Leafy Vegetables: They are good sources of b- carotene, calcium, riboflavin, folic acid, ascorbic acid, iron and vitamin K.
Roots and Tubers: They are good sources of calories and fairly good sources of Vitamin C. eg. Potato,. Carrots etc.
Other Vegetables: They contribute to the fibre content of the diet. Ladies finger and cluster beans are a good source of folic acid.(eg.) Brinjal, Ladies finger, etc.
They are used in curries, salads, and in sambar.
They are used as garnishing agents.
They are used as stuffing in samosas and parathas.
They are used as thickening agents in gravies and soups.
They are used in chutneys and pickles.
Fruits are the ripened ovary or ovaries of a plant together with adjacent tissues. Fruits are fleshy or pulpy in character, often juicy and usually sweet with fragrant, aromatic flavours.
Fruits are very poor source of protein and fat . They are good source of fibre, b- carotenes and vitamin C.
Raw, whole or cut fruits are frequently served as an appetiser, or as a salad or for dessert. Some fruits are served in the form of juices or milk shakes. Sometimes apples are served as stewed apples.
Milk is one food for which there seems to be no adequate substitute. The milk products include curd, butter, skimmed milk, condensed milk, khoa, paneer and cheese.
Milk is a complex mixture of lipids, carbohydrates, proteins and many other organic compounds and inorganic salts dissolved or dispersed in water. The chief carbohydrate present in milk is lactose, a disaccharide although trace amounts of glucose, galactose and other sugars are also present. The protein present in milk is caesin.
Milk provides 67 calories and 3.2 grams of protein per 100ml. Milk has good quality protein. Dairy foods are a major source of calcium and riboflavin.
The ratio of calcium : phosphorus in milk is regarded as most favourable for bone development. In addition, dairy products contain other nutrients such as vitamin D and lactose which favour calcium absorption.
Milk is not a good source of niacin, but it is an excellent source of tryptophan. Milk is a very poor source of vitamin C and iron.
Prevention of scorching or burning - Too thin vessels and too high a temperature can scorch the milk at the bottom of the vessel. Use double boilers or stir constantly.
Prevention of scum formation - This can be achieved by covering the pan, stirring or using milk cooker.
Pasteurization: The microorganisms present in milk are killed using a method called pasteurization, where milk is heated to 65 o C for 30 minutes or 72 o C for 15 seconds and cooled rapidly.
Milk contributes to the nutritive value of the diet.
It adds taste and flavour to the product.
Milk is used in dessert.
Curd or buttermilk is used as leavening agent and to improve the texture.
Curd or buttermilk is given to patients with diarrhoea.
Although eggs of all birds may be eaten, the egg of chicken is used more often than any other birds.
The chief protein of egg white are ovalbumin, conalbumin, ovamucin and avidin. The major proteins in egg yolk are lipoprotein which includes lipoviteliins and lipovitellinin. The fat in the egg yolk contains triglycerides and phospholipids (ie) lecithin.
Nutritive value of egg / 100 g
Energy (Kcal) 173
Protein (g) 13.3
Fat (g) 13.3
Calcium (mg) 60.0
Phosphorus (mg) 220.0
Iron (mg) 2.1
Retinol (mcg) 420
Thiamine (mg) 0.1
Riboflavin (mg) 0.4
Niacin (mg) 0.1
Folic acid (mcg) 78.3
Vitamin BI2 (mcg) 0.2
One egg weighs between 40-50g. Egg contains good quality protein. Egg yolk is a good source of iron, vitamin A, riboflavin, folic acid and vitamin B12.
Eggs are used as
boiled , scrambled or poached for table use.
thickening agent (eg) custards.
Emulsifying agent (eg) Mayonnaise.
Leavening agent (eg) cakes.
Binding and coating agent, (eg) cutlets.
Interfering substances (eg) ice creams.
Garnishing agents (eg) soups.
Flavoring agents (eg) custards.
Enriching agent (eg) egg nogs.
Improve colour (eg) custards.
The term flesh foods include meat, poultry and fish, Meat
The term meat refers to the muscles of warm-blooded, four legged animals, the chief ones being cattle, sheep and pigs.
Meat provides 86 calories and 19.4 grams of protein per l00gm. Meat is an excellent source of some of the B complex vitamins. Liver is an excellent source of iron and vitamin A.
Tender cuts of beef, lamb and pork may be cooked by roasting, broiling, pan-broiling, frying, braising, stewing and pressure-cooking.
The term poultry is applied to all birds used as food and includes chicken, duck, geese, turkey and pigeons. Of these chicken and turkey are most commonly used for their meat.
Poultry meat has high protein content and contains all the essential amino acids required for building body tissues. Poultry flesh is a good source of B vitamins and minerals.
Moist heat methods are applied to older and tougher birds and dry heat methods are applied to young tender birds.
Edible fish are categorised as either fin fish or shell fish. Fish is an excellent source of protein. They contain around 20 % protein. Fresh water fish contains n-3 fatty acids, the consumption of which reduces the incidence of heart diseases. Fish is rich in calcium. Fish liver oils are excellent source of vitamins A and D. Fish are good source of niacin and vitamin D.
Fish is usually cooked by dry heat methods of cooking like broiling, baking and frying. Moist heat method is also effectively used to protect the delicate flavour of the fish.
Aromatic food substances, which enhance flavour, are classified into spices, herbs and seasonings. Spices are usually dried roots, barks or seeds used whole, crushed or powdered (eg) cloves. Herbs are usually the fresh leaves (eg) coriander leaves. Seasonings are the bulbs used fresh like onion and garlic.
Spices are used as flavouring agents (eg) garam masala added to pulav.
Spices are used as colouring agents (eg) turmeric added to lime rice.
Spices give pungency (eg) ginger.
They act as preservatives (eg) fenugreek powder added to pickles.
They act as souring agents (eg) dry mango powder.
Spices act as thickening agents (eg) poppy seeds added to kurma.
They have antibacterial and anticarcinogenic properties (eg) turmeric, garlic.
Spices reduce blood sugar and blood cholesterol levels. (eg) fenugreek seeds.
Beverages may be classified according to their functions in the body.
Refreshing (eg) fruit juices.
Nourishing (eg) milk shakes.
Stimulating (eg) coffee and tea.
Soothing (eg) warm milk and hot tea.
Appetising (eg) soups.
Beverages should be served as soon as possible after preparation in order to retain fresh natural flavour.
Hot beverages should be served hot and cold beverages ice cold.
Beverages should be served in attractive glass tumblers.
Beverages must not be diluted too much with either water or ice.
The principle raw materials of beer manufacture are malted barley, rice and corn, which supply carbohydrates for fermentation by yeast into ethyl alcohol and carbon dioxide.
As grapes mature, the wine yeast saccharomyces ellipsoideus naturally accumulates on the skin. When the crushed grape is placed at a temperature of about 27 o C the juice proceeds to ferment yielding ethyl alcohol, carbon dioxide and traces of flavour compounds.