Nutrition and Dietetics Book.pdf

NUTRITION AND DIETETICS HIGHER SECONDARY - FIRST YEAR Untouchability is a sin Untouchability is a crime Untouchability is inhuman TAMILNADU TEXT BOOK CORPORATION College Road, Chennai - 600 006. ©Government of Tamil Nadu First Edition – 2004 CHAIRPERSON Dr. P. Parvathi Easwaran Former Dean of Home Science Retd Prof. & Head, Dept of Food Service Management and Dietetics Avinashilingam Deemed University, Coimbatore 641043. REVIEWERS Mrs Girija Balasundaram Dr. V.Anuradha S.G.Lecturer Reader Dept of Food Service Dept of Home Science Management and Dietetics Queen Mary’ s College Avinashilingam Deemed Chennai – 600 004 University. Coimbatore 641043 AUTHORS Dr. Sheila John Mrs. Sadhana Rajmohan Parimalam Lecturer S.S. Lecturer, Dept of Home Science Dept of Home Science Quaid-E-Millat Govt College for Women’ s Christian College Women, Chennai-600 002 Chennai - 600 006. Mrs. S. Karthiga Mrs. Anna Rangini Chellappa Lecturer, Dept of Home Science Lecturer, Dept of Home Science Quaid-E-Millat Govt Queen Mary’ s College College for Women Chennai – 600 004 Chennai-600 002 Mrs. B. S. Vasanthi P.G. Assistant (Home Science) Presidency Girls Higher Secondary School, Egmore, Chennai – 600 008 Price: Rs. This book has been prepared by the Directorate of School Education on behalf of Government of Tamilnadu. This book has been printed on 60 G.S.M paper Printed by offset at: PREFACE This book is the outcome of the apt decision of the Directorate of School Education, Government of Tamilnadu to introduce Nutrition and Dietetics as an optional subject at Higher Secondary level. People are becoming nutrition conscious. Print and electronic media pour out nutrition messages to the public. Super markets are flooded with foods of varied types, natural, processed, and ready to eat. The common man turns towards nutrition scientists and dietitians for scientifically proved information on Nutrition and Dietetics. Hence it is essential that Nutrition and Dietetics is offered at various levels of education. This textbook on Nutrition and Dietetics includes content on Food Science and Nutrition at plus one level, while at plus two level on Family Meal Management and Dietetics. At plus one level the student learns the rudimentary aspects while at plus two level the application aspects are included. The contents are so arranged that the student gains knowledge with application and skill. The authors collected scientifically proved and updated information from various authentic sources. The reviewers and chairman offered valuable suggestions on the write up. It is hoped that the students will understand Nutrition and Dietetics in the right perspective using this book. Grateful acknowledgement is expressed to the Director and Joint Director, School Education, Government of Tamilnadu for this enriching opportunity. 1. FOOD GROUPS – A GUIDE IN MENU PLANNING Food is the basic necessity of man. It is a mixture of different nutrients such as carbohydrate, protein, fat, vitamins and minerals. These nutrients are essential for growth, development and maintenance of good health throughout life. They also play a vital role in meeting the special needs of pregnant and lactating women and patients recovering from illness. 1.1 FUNCTIONS OF FOOD Food may be classified according to their functions in the body. Functions of Food ___________________________________ Physiological Social Psychological functions functions functions ________________________________________ Energy yielding Body building foods Protective foods Foods (Protein) (Vitamins and (Carbohydrate, minerals) protein, fat) Fig1.1 Functions of food 1 Physiological functions of food: i. Energy yielding foods: Foods rich in carbohydrates and fats are called energy yielding foods. They provide energy to sustain the involuntary processes essential for continuance of life, to carry out various professional, household and recreational activities and to convert food ingested into usable nutrients in the body. The energy needed is supplied by the oxidation of foods consumed. Cereals, roots and tubers, dried fruits, oils, butter and ghee are all good sources of energy. ii. Body building foods: Foods rich in protein are called body building foods. Milk, meat, eggs and fish are rich in proteins of high quality. Pulses and nuts are good sources of protein but the protein is not of high quality. These foods help to maintain life and promote growth. They also supply energy. iii. Protective and Regulatory foods: Foods rich in protein, minerals and vitamins are known as protective and regulatory foods. They are essential for health and regulate activities such as maintenance of body temperature, muscle contraction, control of water balance, clotting of blood, removal of waste products from the body and maintaining heartbeat. Milk, egg, liver, fruits and vegetables are protective foods. Social functions of food: Food has always been the central part of our community, social, cultural and religious life. It has been an expression of love, friendship and happiness at religious, social and family get-togethers. Psychological functions of food: In addition to satisfying physical and social needs, foods also satisfy certain emotional needs of human beings. These include a sense of security, love and acceptance. For example, preparation of delicious foods for family members is a token of love and affection. 2 Fig.1.2 -Functions of food 3 1.2 ICMR FIVE FOOD GROUPS TABLE – 1.A Five Food Group System Food Group Main Nutrients I. Cereals, Grains and Products : Energy, protein, Rice, Wheat, Ragi, Bajra, Maize, Invisible fat Vitamin – Jowar, Barley, Rice flakes, Wheat B1, Vitamin – B2, Folic flour. Acid, Iron, Fibre. II. Pulses and Legumes : Energy, Protein, Bengal gram, Black gram, Green Invisible fat, Vitamin – gram, Red gram, Lentil (whole as B1, Vitamin – B2, Folic well as dhals) Cowpea, Peas, Acid, Calcium, Iron, Rajmah, Soyabeans, Beans. Fibre. III. Milk and Meat Products : Protein, Fat, Vitamin – Milk : B12, Calcium. Milk, Curd, Skimmed milk, Cheese Meat : Chicken, Liver, Fish, Egg, Meat. Protein, Fat, Vitamin – B2 IV. Fruits and Vegetables : Fruits : Mango, Guava, Tomato Ripe, Carotenoids, Vitamin – Papaya, Orange. Sweet Lime, C, Fibre. Watermelon. Vegetables (Green Leafy) : Amaranth, Spinach, Drumstick Invisible Fats, leaves, Coriander leaves, Mustard Carotenoids, Vitamin – leaves, fenugreek leaves. B2. Folic Acid, Calcium, Other Vegetables : Iron, Fibre. Carrots, Brinjal, Ladies fingers, Capsicum, Beans, Onion, Drumstick, Cauliflower. Carotenoids, Folic Acid, Calcium, Fibre 4 Food Group Main Nutrients V. Fats and Sugars : Fats : Butter, Ghee, Hydrogenated oils, Energy, Fat, Essential Cooking oils like Groundnut, Fatty Acids Mustard, Coconut. Sugars : Sugar, Jaggery Energy Source : Gopalan. C, Rama Sastri B.V. and Balasubramanian S.C., 1989, Nutritive Value of Indian Foods, National Institute of Nutrition, ICMR, Hyderabad. Significance of the five-food group system The five food group system can be used for the following purposes : i. Planning wholesome balanced menus to achieve nutritional adequacy. ii. Assessing nutritional status – a brief diet history of an individual can disclose inadequacies of food and nutrients from any of the five groups. Based on the assessment, nutrition education can be imparted to the individual. 1.3. FOOD PYRAMID : The food guide pyramid was introduced in 1992 by USDA (United States Department of Agriculture) as a general plan of what to eat each day. The food guide pyramid is a valuable tool for planning a health promoting diet. By incorporating the principle of balance, variety and moderation, an individual can still eat their favourite foods while following the food guide pyramid. 5 Sugar and oil Milk and Meat Pulses Fruits and Vegetables Cereals Fig.1.3 -Food guide pyramid Source: Srilakshmi.B 2003.Dietetics, New Age International (P) Publishers Ltd.Chennai. Balance: It means choosing food from different food groups. 6 Variety: This means including different foods within each food group. For eg. consuming a variety of fruits. Moderation: This means keeping serving sizes reasonable. This involves self control. The food guide pyramid provides recommendation for the number of daily servings that should be consumed from each of the food groups. The diagram Fig. 1.3, clearly represents that cereals should form the major bulk of the diet followed by fruits and vegetables, pulses, milk and meat products and sugars and oil. The portion size of foods for adolescents (13-18 years) is given below. TABLE 1.B Portion size of foods for adolescents Number of Portions for Food Groups Portion Size Adolescents Girls Boys Cereals and millets 30 g 10 14 Pulses 30 g 2 2 Milk 100 ml 5 5 Roots and tubers 100 g 1 2 Green leafy 100 g 1 1 Vegetables Other vegetables 100 g 1 1 Fruits 100 g 1 1 Sugar 5g 6 7 Fats and oils 5g 5 5 (For non-vegetarians substitute one pulse portion with one portion (50 gm) of egg / meat / chicken / fish.) Source : Dietary guidelines for Indians – A manual (1998), National Institute of Nutrition, ICMR, Hyderabad – 500 007. 7 Questions Part- A Fill in the blanks: 1. Foods rich in carbohydrate and fats are called ______ foods. 2. Foods rich in ________ are called body building foods. 3. Foods rich in protein vitamins and minerals are called ___________ foods. 4. The food guide pyramid is based on the principles of ________ , __________ and ___________. Part- B Write short answers: 1. How are foods classified?. Mention the physiological functions of food. 2. Give the ICMR classification of food groups. 3. List the major nutrients present in fruits and vegetables. 4. Give the portion size of foods for adolescents. Part- C Write detailed answers: 1. Explain the functions of food. Enumerate the purpose of the five-food group system. 2. Give a diagrammatic representation of the food pyramid and highlight its role as a guide in menu planning. 8 2. COOKING METHODS – MERITS AND DEMERITS Food preparation is an important step in meeting the nutritional needs of the family. Food has to be pleasing in appearance and taste in order to be consumed. Foods like fruits, vegetables and nuts can be eaten raw but most foods are cooked to bring about desirable changes. The process of subjecting food to the action of heat is termed as cooking. Objectives of Cooking 1. Cooking sterilizes food: Above 40° C the growth of bacteria decreases rapidly. Hence food is made safe for consumption. 2. Cooking softens the connective tissues of meat and the coarse fibre of cereals, pulses and vegetables so that the digestive period is shortened and the gastro intestinal tract is less subjected to irritation. 3. Palatability and food quality is improved by cooking – Appearance, flavour, texture and taste of food are enhanced while cooking. 4. Introduces variety – Different dishes can be prepared with the same ingredients. (Eg.) Rice can be made into biriyani and kheer. 5. Increases food consumption – Cooking brings about improvement in texture and flavour thereby increasing consumption of food. 6. Increases availability of nutrients – Example in raw egg, avidin binds biotin making it unavailable to the body. By cooking, avidin gets denatured and biotin is made available. 9 2.1 COOKING METHODS Heat is transferred to the food during cooking by conduction, convection, radiation or microwave energy. Cooking takes place by moist and dry heat. Moist heat involves water and steam. Air or fat are used in dry heat. TABLE – 2A Cooking methods Moist Heat Dry Heat Combination Boiling Roasting Braising Stewing Grilling Steaming Toasting Pressure Cooking Baking Poaching Sauteeing Blanching Frying 2.2 MOIST HEAT METHODS 2.2.1 Boiling: Boiling is a method of cooking foods by just immersing them in water at 100° C and maintaining the water at that temperature till the food is tender. Rice, egg, dhal, meat, roots and tubers are cooked by boiling. Merits 1. Simple method - It does not require special skill and equipment. 2. Uniform cooking can be achieved. Demerits 1. Continuous excessive boiling leads to damage in the structure and texture of food. 2. Loss of heat labile nutrients such as B and C vitamins if the water is discarded. 3. Time consuming – Boiling takes more time to cook food and fuel may be wasted. 4. Loss of colour – water soluble pigments may be lost. 10 2.2.2 Stewing It refers to the simmering of food in a pan with a tight fitting lid using small quantities of liquid to cover only half the food. This is a slow method of cooking. The liquid is brought to boiling point and the heat is reduced to maintain simmering temperatures (82°C - 90° C). The food above the liquid is cooked by the steam generated within the pan. Apple, meat along with roots, vegetables and legumes are usually stewed. Merits 1. Loss of nutrients is avoided as water used for cooking is not discarded. 2. Flavour is retained. Demerits 1. The process is time consuming and there is wastage of fuel. 2.2.3 Steaming: It is a method of cooking food in steam generated from vigorously boiling water in a pan. The food to be steamed is placed in a container and is not in direct contact with the water or liquid. Idli, custard and idiappam are made by steaming. Vegetables can also be steamed. Merits 1. Less chance of burning and scorching. 2. Texture of food is better as it becomes light and fluffy. Eg. Idli. 3. Cooking time is less and fuel wastage is less. 4. Steamed foods like idli and idiappam contain less fat and are easily digested and are good for children, aged and for therapeutic diets. 5. Nutrient loss is minimised. Demerits 1. Steaming equipment is required. 2. This method is limited to the preparation of selected foods. 11 2.2.4 Pressure cooking: When steam under pressure is used the method is known as pressure cooking and the equipment used is the pressure cooker. In this method the temperature of boiling water can be raised above 100° C. Rice, dhal, meat, roots and tubers are usually pressure cooked. Merits 1. Cooking time is less compared to other methods. 2. Nutrient and flavour loss is minimised. 3. Conserves fuel and time as different items can be cooked at the same time. 4. Less chance for burning and scorching. 5. Constant attention is not necessary. Demerits 1. The initial investment may not be affordable to everybody. 2. Knowledge of the usage, care and maintenance of cooker is required to prevent accidents. 3. Careful watch on the cooking time is required to prevent over cooking. 2.2.5 Poaching: This involves cooking in the minimum amount of liquid at temperatures of 80° C - 85° C that is below the boiling point. Egg and fish can be poached. Merits 1. No special equipment is needed. 2. Quick method of cooking and therefore saves fuel. 3. Poached foods are easily digested since no fat is added. Demerits 1. Poached foods may not appeal to everybody as they are bland in taste. 2. Food can be scorched if water evaporates due to careless monitoring. 3. Water soluble nutrients may be leached into the water. 12 2.2.6 Blanching: In meal preparation, it is often necessary only to peel off the skin of fruits and vegetables without making them tender. This can be achieved by blanching. In this method, food is dipped in boiling water for 5 seconds to 2 minutes depending on the texture of the food. This helps to remove the skin or peel without softening food. Blanching can also be done by pouring enough boiling water on the food to immerse it for some time or subjecting foods to boiling temperatures for short periods and then immediately immersing in cold water. The process causes the skin to become loose and can be peeled off easily. Merits 1. Peels can easily be removed to improve digestibility. 2. Destroys enzymes that bring about spoilage. 3. Texture can be maintained while improving the colour and flavour of food. Demerits 1. Loss of nutrients if cooking water is discarded. 2.3 DRY HEAT METHODS 2.3.1 Roasting: In this method food is cooked in a heated metal or frying pan without covering it. Eg. Groundnut. Merits 1. Quick method of cooking. 2. It improves the appearance, flavour and texture of the food. 3. Spices are easily powdered if they are first roasted. Demerits 1. Food can be scorched due to carelessness. 2. Roasting denatures proteins reducing their availability. 2.3.2 Grilling: Grilling or broiling refers to the cooking of food by exposing it to direct heat. In this method food is placed above 13 or in between a red hot surface. Papads, corn, phulkas, chicken can be prepared by this method. Merits 1. Enhances flavour, appearance and taste of the product. 2. It requires less time to cook. 3. Minimum fat is used. Demerits 1. Constant attention is required to prevent charring. 2.3.3 Toasting: This is a method where food is kept between two heated elements to facilitate browning on both sides. Bread slices are cooked by toasting. Merits 1. Easy and quick method. 2. Flavour improved. Demerits 1. Special equipment required. 2. Careful monitoring is needed to prevent charring. 2.3.4 Baking: In this method, the food gets cooked in an oven or oven- like appliance by dry heat. The temperature range maintained in an oven is 120°C – 260°C. The food is usually kept uncovered in a container greased with a fat coated paper. Bread, cake, biscuits, pastries and meat are prepared by this method. Merits 1. Baking lends a unique baked flavour to foods. 2. Foods become light and fluffy – cakes, custards, bread. 3. Certain foods can be prepared only by this method – bread, cakes. 4. Uniform and bulk cooking can be achieved. Eg. bun, bread. 5. Flavour and texture are improved. 6. Variety of dishes can be made. 14 Demerits 1. Special equipment like oven is required. 2. Baking skills are necessary to obtain a product with ideal texture, flavour and colour characteristics. 3. Careful monitoring needed to prevent scorching. 2.3.5 Sauteing: Sauteing is a method in which food is lightly tossed in little oil just enough to cover the base of the pan. The pan is covered with a lid and the flame or intensity of heat is reduced. The food is allowed to cook till tender in its own steam. The food is tossed occasionally, or turned with a spatula to enable all the pieces to come in contact with the oil and get cooked evenly. The product obtained by this method is slightly moist and tender but without any liquid or gravy. Foods cooked by sauteing are generally vegetables which are used as side dishes in a menu. Sauteing can be combined with other methods to produce variety in meals. Merits 1. Takes less time. 2. Simple technique. 3. Minimum oil is used. Demerits 1. Constant attention is needed as there is chance of scorching or burning. 2.3.6 Frying: In this method, the food to be cooked is brought into contact with larger amount of hot fat. When food is totally immersed in hot oil, it is called deep fat frying. Samosa, chips, pakoda are examples of deep fat fried foods. In shallow fat frying, only a little fat is used and the food is turned in order that both sides are browned. Eg. Omlette, cutlets, parathas. 15 Merits 1. Very quick method of cooking. 2. The calorific values of food is increased since fat is used as the cooking media. 3. Frying lends a delicious flavour and attractive appearance to foods. 4. Taste and texture are improved. Demerits 1. Careful monitoring is required as food easily gets charred when the smoking temperature is not properly maintained. 2. The food may become soggy due to too much oil absorption. 3. Fried foods are not easily digested. 4. Repeated use of heated oils will have ill effects on health. 2.4 COMBINATION OF COOKING METHODS Braising : Braising is a combined method of roasting and stewing in a pan with a tight fitting lid. Flavourings and seasonings are added and food is allowed to cook gently. Food preparations prepared by combination methods are : Uppuma - Roasting and boiling. Cutlet - Boiling and deep frying. Vermicilli payasam - Roasting and simmering. 2.5 MICROWAVE COOKING Microwaves are electromagnetic waves of radiant energy with wave lengths in the range of 250 x 106 to 7.5 x 109 Angstroms. The most commonly used type of microwave generator is an electronic device called a magnetron which generates radiant energy of high frequency. A simple microwave oven consists of a metal cabinet into which the magnetron is inserted. The cabinet is equipped with a metal fan that distributes the microwave throughout the 16 cabinet. Food placed in the oven is heated by microwaves from all directions. Fig. 2. 1- Microwave oven 1.Door release button 2. See –through window 3. Door safety lock system 4.External air vents 5.Control panel 6.Identification plate 7.Glass tray 8.Roller ring Source: Srilakshmi B.(2003) Food Science , New Age International (P) Publishers Limited.Chennai. Moist foods and liquid foods can be rapidly heated in such ovens. Food should be kept in containers made of plastic, glass or china ware which do not contain metallic substances. These containers are used because they transmit the microwaves but do not absorb or reflect them. Merits 1. Quick method – 10 times faster than conventional method. So loss of nutrients can be minimised. 2. Only the food gets heated and the oven does not get heated. 3. Food gets cooked uniformly. 17 4. Leftovers can be reheated without changing the flavour and texture of the product. 5. Microwave cooking enhances the flavour of food because it cooks quickly with little or no water. Demerits 1. Baked products do not get a brown surface. 2. Microwave cooking cannot be used for simmering, stewing or deep frying. 3. Flavour of all ingredients do not blend well as the cooking time is too short. 2.6 SOLAR COOKING Solar cooking is a very simple technique that makes use of sunlight or solar energy which is a non-conventional source of energy. Solar cooker consists of a well insulated box which is painted black on the inside and covered with one or more transparent covers. The purpose of these transparent covers is to trap heat inside the solar cooker. These covers allow the radiation from the sun to come inside the box but do not allow the heat from the hot black absorbing plate to come out of the box. Because of this, temperature upto 140°C can be obtained which is adequate for cooking. Merits 1. Simple technique – requires no special skill. 2. Cost effective as natural sunlight is the form of energy. 3. Original flavour of food is retained. 4. There is no danger of scorching or burning. 5. Loss of nutrients is minimum as only little amounts of water is used in cooking. Demerits 1. Special equipment is needed. 2. Slow cooking process. 3. Cannot be used in the absence of sunlight – rainy season, late evening and night. 18 Fig. 2.2-Solar cooker 1.Solar plane mirror 2.Cooking container3.Glass sheet 4. Cover 5. Insulation material glass 6.Outer box 7. Handle 8.Mirror support 9.Hinged adjuster and guide Source: Srilakshmi B.(2003) Food Science , New Age International (P) Publishers Limited.Chennai. 19 QUESTIONS Part- A Fill in the blanks: 1. ________ is a method of cooking foods by just immersing then in water at 100º C 2. Simmering of food in a pan with a tight fitting lid using small quantities of liquid to cover only half the food is known as ___________ 3. When steam under pressure is used the method is known as _________ 4. ___________ is a method use to prepare cakes. 5. When food is totally immersed in hot oil, it is called _________. 6. ________ is a combined method of roasting and stewing in a pan with a tight fitting lid Part- B Write short answers 1. What are the objectives of cooking food? 2. Bring out the differences between stewing, steaming and sauteing. 3. What is the best method of preparing rice and dhal? Justify your choice of cooking method. 4. Write a note on solar cooking and its merits and demerits Part- C Write detailed answers 1. Compare the various moist heat methods of cooking. Highlight the merits and demerits of each type. 2. Give a brief account about the principles, merits and demerits of microwave cooking. 3. Explain the cooking method employed in the preparation of (a) Bread, (b) Idli, (c) Chapathis 4. Discuss the dry heat methods of cooking? 20 3. CEREAL AND CEREAL PRODUCTS Cereals form the staple food of the human race. In India wheat, rice, maize (corn), oats, jowar, ragi and bajra are the common cereals and millets used. 3.1 STRUCTURE OF RICE AND WHEAT The overall structure of all cereal grains is basically similar. Rice grains resemble wheat but is smaller than that of wheat. It is flattened laterally and has no ventral furrow. Wheat cereal grains are composed of an outer bran coat, a germ and a starchy endosperm. rice wheat a. Bran b. Endosperm c. Germ Fig. 3.1 Structural Parts of rice and wheat Source: Sumati Mudambi, R and Shalini, M. Rao 1989 Food Science. New Age International (P) Publishers Ltd, Chennai. 21 The longitudinal structure of wheat grain depicting the various layers is represented diagrammatically in fig.3.2 Fig. 3.2 Longitudinal structure of wheat grain Source: Srilakshmi B. 2003 Food Science. New Age International (P) Publishers Ltd Chennai. Bran: Bran is the outer layer of the kernel and constitutes 5 percent of the kernel. During milling the bran is discarded. Bran is rich in fibre and minerals. It is also a good source of thiamine and riboflavin. Aleurone Layer: This is located just under the bran, which is rich in protein, phosphorus and thiamin and contains moderate amounts 22 of fat. The aleurone layer makes up about 8 percent of the whole kernel. This layer is lost in the milling process along with bran. Endosperm: This is the large central part of the kernel and constitutes 84 – 85 percent of the kernel. The endosperm cell consists mainly of starch and protein and little mineral matter and fibre and only half a trace of fat. The vitamin content of the endosperm is low. Germ : This is a small structure at the lower end of the kernel and is separated from the endosperm by the scutellum. It makes up 2 – 3 percent of the whole kernel. It is rich in protein, fat, vitamins and minerals. The germ serves as a store of nutrients for the seed when it germinates. During milling some of the germ is lost along with the bran and aleurone layer. 3.2 NUTRITIVE VALUE OF CEREALS Cereals are an important and economic source of energy. Hundred grams of cereals supply 340 kilo calories of energy. Cereals are also a significant source of proteins (8 – 11 percent) in the diets of people whose staple food is cereals. However, cereal protein is incomplete as it lacks an essential amino acid, lysine. This lack is made up when cereals are eaten along with other protein foods such as dhals, pulses and milk. Wheat flour contains glutelin and gliadin as proteins which are commonly known as gluten. The strength of the wheat flour is based on the quality of gluten used. Whole grains chiefly furnish starch, proteins, minerals, B -Vitamins and fibre. Refined cereals lose part of the protein, minerals, and B - Complex vitamins in milling. They contain a little more starch than whole cereals. 23 Whole grains contain more vitamins, minerals and fibre than refined grain and are valuable dietary sources of iron, phosphorus, thiamine and fibre. 3.3 PARBOILING AND MILLING – EFFECT ON NUTRIENT CONTENT Parboiling is a process of soaking paddy in water at 65° - 70° C for 3 – 4 hours. The water is drained and the soaked paddy is steamed in the same vessel for 5 to 10 minutes. The paddy is dried in the sun or mechanically dried. Advantages of Parboiling: 1. Dehusking of parboiled rice is easy. 2. Grains become tougher resulting in reduced losses during milling. 3. Part of the scutellum and germ which are rich in B – Vitamins get fixed to the grain and hence loss of B – Vitamins are less. The retention of thiamine, riboflavin, niacin and folic acid in parboiled rice is greater than that of polished or hand pounded rice. 4. It improves digestibility. 5. It swells more when cooked to desired softness. Milling: Milling is the process, which removes the coarse outer layer of bran and germ. Paddy is milled by hand pounding or mechanical rice millers. The process of milling involves the following steps. Rice is passed through two stone or rubber discs rotating at different speeds and by shearing action on the grain, the hull is pulled away. The whole kernel from which the hulls have been removed is known as brown rice. This is then milled in a machine called pearler to remove coarse outer layers of bran and germ by a process of rubbing, resulting in unpolished milled rice. Some amount of breakage of rice occurs in this milling. 24 Unpolished rice is liable to develop rancidity and so it is polished in a brush machine which removes the aleurone layer and yields “polished rice”. Sometimes the polished rice is further treated in a device known as trumbol to give a coating of sugar and talc to produce a brighter shine on the grains. Rice is separated from the broken kernels. Large kernels are called second heads, medium ones are called screenings, smallest ones are called the brewers rice. The percentage loss of different nutrients during milling are protein 15% fat 82% thiamine 85% riboflavin 70% pyridoxine (Vitamin B6) 50%. The degree of milling determines the amount of nutrients removed. Losses during milling can be compensated by the following processes. By under-milling or unpolishing rice the loss of nutrients can be reduced. A second method is that of increasing vitamin retention by processing the rough rice prior to milling. This is done by parboiling which is commercially known as converted rice. Another means of remedying the losses occurring in the milling of rice is the artificial enrichment of the grain. A premix has been developed in which the rice is wetted with a solution of thiamin and niacin, then dried. A second coating of iron pyro phosphate is distributed on the rice. The rice premix is highly resistant to washing, cooking and storage losses. 25 (a) unmilled raw rice (b) Milled raw rice (c) unmilled parboiled rice (d) milled parboiled rice Fig. 3.3 – Effect of milling of raw and parboiled rice (a) Unmilled raw rice - Germ and pericarp are intact in raw rice, Vitamin B1 and other vitamins are concentrated mainly in the germ and pericarp. When these are removed by milling, the grain has lost most of its vitamins. (b) Milled raw rice – Germ and pericarp are removed (c) Unmilled parboiled rice- The vitamin has diffused through the endosperm 26 (d) Milled parboiled rice : Although germ and pericarp have been removed, the grains still contains most of the vitamins 3.4 NUTRIENT CONTENT OF RAGI, MAIZE, AND JOWAR Ragi : Ragi or finger millet is widely consumed without any refining by many people in rural areas. It contains B Vitamins but is poor in thiamine. Ragi is rich in minerals especially calcium. It is also rich in fibre and is a fair source of iron. Maize or corn : Maize, like any other cereal is rich in calories. It is deficient in amino acid lysine. It is a good source of carotene and contains thiamine and folic acid in appreciable amounts. Jowar : Jowar or Sorghum is grown in Maharashtra, Karnataka, Madhya Pradesh, Gujarat, Uttara Pradesh and parts of Tamil Nadu. It is rich in carbohydrate, and B – Complex vitamins. It is poor in vitamin – A and rich in dietary fibre. Compared to rice, jowar is richer in protein but the quality is not as good as rice protein. 3.5 MALTING OF CEREALS Malting is a controlled germination process, which activates the enzymes of the resting grain resulting in the conversion of cereal proteins and other macromolecules. Generally barley is the grain used in the production of malt. Other grains used in the preparation of malt include wheat, jowar and ragi. The process of malting of cereal grain consists of the following steps : 1. Selection of grain and cleaning. 2. Steeping in cold water for 36 hours with 2 to 3 changes in water. 27 3. Germination : The grains are spread on wire mesh trays and kept for 3 days. Water is sprinkled over each of these trays. Amylases and proteases are formed. 4. Kilning : The germinated grains are dried at slow rate on kilns. The amylases act on starch hydrolysing it to dextrin and proteases act on protein hydrolysing them to peptones. Amylase Rich Food (ARF) is germinated cereal flours which are extremely rich in the enzyme alpha – amylase. ARF are excellent weaning foods because they reduce the bulk of weaning foods and are energy dense. 5. Malt is used in pharmaceutical preparations, breakfast cereals, malted milk confectionaries, infant foods, bakery products, candies and in brewing. 3.6 PROCESSED CEREAL PRODUCTS Products of wheat Whole wheat flour: It is obtained by grinding whole wheat. It contains the finely ground bran, germ and endosperm of the whole kernel. Maida: It is refined wheat flour. The bran and germ are separated in making white flour or maida. Maida bakes more uniformly into a loaf of a greater volume and it is more bland in taste and more easily digested. It is used in the manufacture of macaroni products. Semolina: It is coarsely ground endosperm and its chemical composition is similar to that of white flour. Macaroni Products: These products include macaroni, spaghetti, vermicelli and noodles. 28 The starchy endosperm of wheat is coarsely ground into semolina which is made with water into a thick dough. The dough is placed in a cylinder, the lower end of which is fitted with a disc perforated with openings. As the dough is forced through the openings various shapes are formed. Macaroni is a tube form, spaghetti may be either tube or rod, vermicelli is a tiny rod and noodles are flat strips. Malted Wheat: The process of malting helps in the production of malted cereal flour Malted cereal flour is inexpensive and can be made at home as well as commercially. Malt is used in brewing and in the preparation of malt extract for pharmaceutical purposes and in the preparation of malted milk powder. Broken Wheat: Broken Wheat is whole wheat coarsely ground into large particles. As the losses during milling is little, it is a very nutritious food. Rice products: Rice bran: Breakage of the white rice kernel during milling results in small fragments of the endosperm becoming part of the bran fraction. Parboiled rice bran is normally finely granulated and light tan in colour. It has a bland flavour and can be used in the preparation of bread, snacks, cookies and biscuits. In addition, rice bran is a very rich source of dietary fibre. It is therefore an effective stool bulking agent. Rice bran oil : Rice bran oil is obtained by extracting edible grade oil from rice bran. The National Institute of Nutrition, (NIN) Hyderabad has certified that this oil is toxicologically safe for human consumption. This oil is rich in Vitamin E. In addition, it has cholesterol lowering effect than other oils. 29 Puffed Rice: Puffed rice is obtained when sun ripe paddy is filled in earthen jars and is moistened with hot water. After 2-3 minutes the water is decanted and the jars are then kept in an inverted position for 8-10 hours. The paddy is exposed to sun for a short time and then parched in hot sand at 190 -210º C for 40-45 seconds. During parching, the grains swell and burst into soft white products. The parched grains are sieved to remove sand and winnowed to separate the husk. Rice flakes: Rice flakes are made after soaking the paddy in hot water, parching it by roasting and then flattening it by force while it is hot to form flakes. It retains a large part of iron and B-vitamin of the aleurone layer. The roasting helps to toast the grain, resulting in partial cooking of the grain. It needs very little time to prepare and is used as a snack. It should be free from bran, broken particles, fragments of the seed coat, insects, stones, trash and bad odour. Products of Maize Corn oil: Corn oil is extracted from corn germ. Corn or maize oil is a highly desired vegetable oil owing to its relatively high level of linolenic fatty acid and its excellent flavour. Popcorn: Popcorn is prepared by heating the kernels of corn. During heating, the water vapour within them expands, increasing the pressure until it is sufficient to make the kernels explode or “pop”. It is used as a snack for children. Popping can be done with or without fat. Corn starch: It is made by a process of wet milling in which the hull and germ are removed. The corn is then ground and mixed with water. The semi liquid material is separated by passing it over 30 sieves or centrifuging it. The starch settles out while most of the protein remains suspended. The starch is then washed, dried and powdered. Corn starch is widely used because it is inexpensive, lacks characteristic flavour and cooks to a smooth and almost clear paste in water or other clear liquid and superior to wheat flour or potato starch. 3.7 FERMENTED CEREAL PRODUCTS The term fermentation refers to the breakdown of carbohydrate like matter under either aerobic or anaerobic conditions. The organisms involved may be bacteria or moulds. During fermentation microorganisms produce gas and help in leavening the batter or dough. They also produce flavouring substances. Advantages of Fermentation: 1. Flavour and texture of the product is improved. 2. Vitamin B and C content is increased. 3. The product is easily digestible. 4. Acid by-products formed during fermentation inhibits the growth of harmful microorganisms. 5. Variety in the diet:- Traditional Indian recipes like idli, dosa, appam, dhokla and rice vadam are cereal based fermented products. Idli : Idli is a fermented and steamed food prepared using parboiled rice and black gram dhal in proportion of 3 : 1. The ingredients are ground separately, mixed together and allowed to ferment overnight. Fermentation is facilitated by bacteria such as Lactobacillus lactis, Streptococcus lactis and Leuconostoc mesenteroides. The mucilagenious material in black gram dhal helps in the retention of carbon- dioxide during fermentation. Dosai : This is prepared from a fermented batter of rice and black gram (4:1). Ingredients are ground fine and salt is added and fermented overnight. 31 Dhokla : It is prepared using rice and bengalgram dhal. The ingredients are soaked, ground coarsely and fermented overnight. The batter is steamed in a pie-dish and cut into desired shapes and garnished. Appam: It is a rice batter fermented with yeast and coconut milk or coconut water and cooked in a special appam kadai by covering with a dome shaped lid. Rice vadam : This is prepared by using left over cooked rice, which is soaked in excess water and allowed to ferment overnight. The water is drained and rice is mashed. Finely cut onions, chillies and lime are added and it is made into small vadam and sun- dried. Bread : Flour, water, milk, salt, sugar, butter and yeast are the ingredients used in the preparation of bread. All the ingredients are mixed and allowed to rise. Fermentation is effected by the action of yeast enzyme zymase on the glucose in the dough producing alcohol and carbon dioxide. The fermented dough is kneaded by hand (knock-back) to remove gas, redistribute yeast cells, subdivide gas cells and increase the uniformity in size. The fermented dough is then sized, shaped and placed in pans for proofing at 38° C - 48° C for 45 – 60 minutes and baked for 30 minutes at 204° C – 232° C 3.8 ADVANTAGES OF INCLUDING A COMBINATION OF CEREALS IN THE MENU Cereals are the main source of energy in Indian diets contributing 70 – 80 percent of daily energy intake of majority of Indians. The major cereals consumed in India are rice, wheat, jowar, bajra and ragi. 32 Rice is the staple diet of South Indians. However, rice among the cereals is a poor source of calcium and iron. Whole wheat is a fair source of protein and fibre. Although rice contains less protein when compared to other cereals, its protein quality is better than that of other cereals. Ragi is rich in minerals especially calcium. Millets including ragi are rich in minerals and fibre. Inclusion of millets will help in making up deficiencies of some minerals in the diet besides providing bulk to the diet, particularly rice based ones. The nutritive value of cereals varies with the part of the grain used. All whole cereals furnish starch, protein, iron, phosphorus, thiamin and fibre but refined cereals lose part of these nutrients during the milling process. A judicious combination of different cereals in the days diet will help to meet the nutrient requirements. For example wheat dosai, rice flakes payasam, ragi adai and broken wheat uppuma can be included in the menu instead of rice-based meals alone. Batters used for idli and dosai and doughs used for chappathis can be prepared using a combination of cereal flours. This will contribute different nutrients to the days diet. 3.9 ROLE OF CEREALS IN COOKERY Cereals form the staple diet and contribute to most of the calorie requirement and half of the protein requirement. Cereals improve the quality of pulse protein. They are excellent source of starch and B vitamins. Cereals also contribute to satiety and are used to prepare the main dish. No meal can be made without cereals. Cereals are used as thickening agent, e.g. corn flour in custards, corn flour in white sauce, macaroni in soups. Cereals are used as coating agent, e.g., maida paste in cutlets or bread crumbs in cutlets. 33 Cereals are used in sweet preparations, e.g., rice, payasam, wheat halwa. Malted cereals are used in the preparation of beverages and weaning foods. Cereals products like corn flakes and rice flakes are used as ready to use foods. Fermented foods made from cereals are used as breakfast foods or snacks, e.g., idli, dhokla. QUESTIONS Part-A Fill in the blanks: 1) ________________ is the outer layer of the kernel. 2) Cereals are deficient in amino acid _______________. 3) Parboiling reduces the loss of vitamins _____________. 4) The process of removing bran and germ is called ____________. 5) _____________ is a controlled germination process which activates the enzymes of the resting grain. Part-B Write short answers 1) Define parboiling. Highlight its advantages. 2) What are the advantages of fermentation? 3) Discuss the advantages of including a combination of cereals in the menu. 4) Explain the roles of cereals in cookery? 34 Part-C Write detailed answers 1) Discuss the nutrient content and structure of cereals. 2) Compare the nutritional significance of rice and ragi. 3) What is fermentation? What are the cereal products prepared by fermentation? 4) How is malting done? Explain the process. 5) Discuss the role of cereals in cookery. Highlight the advantage of including combination of cereals in the days menu. 6) Give a detailed account on the different types of processed cereal products? 7) How is milling done? How can nutrient losses be prevented in milling? 35 4. PULSES Pulses are the edible fruits or seeds of pod-bearing leguminous plants. The term pulse in India is used for edible legumes and dhal is used for decuticled split legumes. Bengal gram, red gram, black gram, green gram, lentil, horse gram, peas and kesari dhal are some of the major pulse crops in India. Soyabean is also grown. 4.1 NUTRIENT CONTENT OF PULSES Pulses give 340 calories per 100 gm which is almost similar to cereal calorie. They are a rich source of protein containing about 18 – 25 percent protein. Soyabean is an exception containing about 35 to 40 percent protein. All pulses contain sufficient amount lysine which is deficient in cereals and therefore they can supplement cereal protein. A mixture of cereals and pulses is superior to that of either one. Hence a combination of cereals and pulses is ideal for human consumption. Pulses contain 55 – 60 percent of carbohydrate including starch soluble sugar and fibre. They contain 1.5 percent lipids. Pulses also contain calcium, magnesium, zinc, iron, potassium and phosphorus. They are a poor source of carotene and vitamin C but fairly rich in niacin. Germination increases the vitamin C content of pulses. The thiamine content of pulses is equal to or exceeds that of cereals. Being rich in B - Vitamins, they contribute significantly to B – Vitamin intake. 4.2 TOXIC SUBSTANCES IN PULSES Some toxic substances are naturally present in some pulses. These include trypsin inhibitors and haemagglutinins. Trypsin 36 inhibitor, as the name indicates, interferes with digestion of proteins by inhibiting the action of the enzyme trypsin. Haemagglutinins combine with haeme and thus destroy haemoglobin. Fortunately, both of these toxic substances are destroyed by heat, which is used in the normal cooking process. Broad beans contain some toxic substances. When these beans are consumed raw a disease called favism occurs. This disease is characterized by haemolytic anemia. Since human beings usually do not consume broad beans raw, they are not likely to suffer from favism. Kesari dhal also contains a toxic substance. This dhal is grown in Madya Pradesh(M.P) It was observed that during the drought conditions, only this dhal is grown and used as a staple food. When this dhal is consumed over a long time paralysis of lower limbs occurs in males. This is known as lathyrism. It is reported that when the intake of kesari dhal is restricted to 30 per cent of the total calorie intake, no adverse effects are observed. Therefore it is important to ensure that the intake of this dhal must be restricted to a maximum of 30 percent of the total calorie intake. 4.3 GERMINATION – NUTRIENT ENHANCEMENT Germination is a process that involves the soaking of pulses overnight. The water is then drained and the seeds are tied in a loosely woven cotton bag and hung. Water is sprinkled twice or thrice a day and sprouts usually appear within 6 – 8 hours. Advantages of germination : 1. Vitamin C is synthesised during germination. The increase in vitamin C is around 7 – 20 mg per 100 gm of pulses. 2. Riboflavin, niacin, choline and biotin are increased. 3. Starch is converted into sugars. 4. It reduces the anti-nutritional and toxic factor in pulses. 37 5. Increased variety in the diet as sprouted pulses can be added to salads. 6. Dormant enzymes get activated and digestibility and availability of nutrients is improved. 7. Minerals like calcium, zinc and iron are released from bound form. 8. Sprouted pulses can be eaten raw, since germination improves taste and texture. 4.4 FACTORS AFFECTING PULSE COOKERY 1. Soaking in water hastens the cooking of dried pulses. 2. Soaking in boiling water reduces cooking time as the enzyme phytase present in the legume is inactivated. 3. Hard water prolongs the cooking time of dried pulses. This may be due to the reaction of calcium and magnesium ions in hard water with the pectic constituents of dried beans. 4. Addition of cooking soda (Sodium bicarbonate) will hasten cooking. However this causes loss of thiamine. Excess soda also makes cooked legumes dark and mushy. 5. Addition of acidic component such as tomato juice tamarind juice prolong the time required to make pulses tender. 6. Cooking time is considerably reduced when pulses are cooked by the use of steam under pressure. 4.5 SOYA PRODUCTS AVAILABLE IN THE MARKET AND THEIR USE Soyabean with its high protein content is considered as a substitute for meat protein which is expensive. Soyabean can be processed to obtain the following food products. 1. SOYA FLOUR: Soyabean is slightly roasted and ground to yield flour. Oil is sometimes removed from the bean to give defatted soya 38 flour which has a higher keeping quality. Soya flour is used in combination with wheat flour in the preparation of chapathis. It can also be incorporated in the batter used in the preparation of bajji, vadai and pakoda. 2. SOYA MILK : The milk is prepared by grinding soaked beans with water. It is then passed through a mill in a stream of water. The emulsion that is obtained is filtered and transferred to a boiler and mixed with vitaminised margarine to which sugar, salt, calcium and malt are added. The mixture is cooked for 20 minutes emulsified and then dried. The white emulsion thus expressed from soyabean has the appearance of milk. 3. SOYABEAN CURD : Tofu or soyabean curd is prepared from soya milk. The curd is precipitated from milk emulsion by adding calcium sulphate. It is allowed to settle, and then it is separated washed and dried. It is a soft delicate structure which can be cut into pieces. It can be used like paneer in various preparations. 4. TEXTURED VEGETABLE PROTEIN (TVP) : Textured Vegetable Protein is prepared using defatted soya flour from which most of the oil and carbohydrates are removed. The flour contains 70 percent protein and is made into dough to which colour and flavour are added. It is at times fortified with vitamins. The dough is extruded through equipment at high temperature and pressure and the product is expanded by sudden release of pressure. The extruded granules are marketed as TVP. It is rehydrated with water before use in the preparation of various vegetarian and non-vegetarian dishes. 5. SOYA PROTEIN ISOLATES Soya protein isolates are protein granules, isolated by processing, It is fortified with vitamins and minerals and used as a complementary food. 39 Apart from these fermented soya products, soya sauce and soya paste are used in the preparation of chinese dishes. 4.6 ROLE OF PULSES IN COOKERY Pulses are rich in protein and B vitamins and improve the quality of cereal protein. Pulses give satiety due to high protein and fibre content. Pulses improve flavour and consistency of dhal sambar and rasam. They contribute to fermentation in preparation of idli and dosa. They are used in snacks like sundal, bajji, panipuri and bhelpuri. They are used in salads, e.g., sprouted gram. They are used in desserts like paruppu payasam and sweets like mysore pak and laddu. They are used as thickening agent e.g., Bengal gram flour in gravies. Roasted pulses are used in making chutneys and chutney powders. They are used as part of seasonings in curries. Questions Part-A Fill in the blanks: 1) Pulses give _________ calories per 100gms. 2). Soyabean contains about _________ percent protein. 3). Pulse protein are deficient in _______ amino acids. 4). All pulses contain sufficient amount of _______which is deficient in cereals. 5). Germination increases the vitamin _________ content of pulses. 40 1) ___________ is a process that involves the soaking of pulses overnight. 2) Addition of cooking soda causes loss of _________in pulses. 3) ___________ is prepared using defatted soya flour from which most of the oil and carbohydrates is removed. Part-B Write short answers 1). Discuss the nutrient content of pulses. 2). Justify the nutritional significance of cereal – pulse combinations. 3). Discuss the role of pulses in cookery. 4). Write a short note on toxic substances in pulses Part- C Write detailed answers 1). What is germination? Explain the effect of germination on the nutrient content pulses? 2). Discuss the factors affecting the cooking quality of pulses. 3). List the products prepared from soyabean and highlight its use in Indian cookery. 41 5. VEGETABLES AND FRUITS India with its diverse, but favourable agroclimatic conditions produces a wide range of tropical and temperate fruits and vegetables. The annual production of these crops is about 53 million tonnes. Vegetables are plants or parts of plants served with the main course of a meal. Apart from the nutritive value, vegetables probably do more than any other group of foods to add appetising colour, texture and flavour to our daily food. With the wide choice of colour of vegetables, it is possible to select a vegetable with a desired colour to highten the appearance of a meal. The texture of a vegetable varies depending upon whether it is served raw are cooked. The texture and appearance of meals can then be varied by the way the vegetable is served. Vegetables contain a wide range of characteristic flavours. By a proper choice of vegetables, the desired flavour of a meal can be obtained. A fruit is the edible and juicy product of a tree or plant and consists of the matured ovary including its seeds and adjacent parts. Usually fruits are sweet, with a wide range of flavours, colours and textures. 5.1 CLASSIFICATION OF VEGETABLES Vegetables can be classified into three groups according to their nutritive value. Ø green leafy vegetables Ø roots and tubers Ø other vegetables 42 VEGETABLES ________________________________________ Green leafy vegetables Roots and tubers Other vegetables (Eg. Agathi, amaranth, (Eg. Potato, (Eg. Brinjal, drumstick leaves, beetroot, onion, bitter gourd cabbage, spinach, Carrot, yam, ladies finger, fenugreek leaves,) tapioca) cauliflower.) Fig.5.1 Classification of vegetables 5.2 NUTRIENT CONTENT OF VEGETABLES AND FRUITS VEGETABLES i. Green Leafy Vegetables : They are an inexpensive rich source of many nutrients such as – carotene, ascorbic acid, folic acid, calcium, iron and fibre. They are a poor source of protein. ii. Roots and Tubers : Roots and tubers are rich in carbohydrates and are a source of energy in the diet. Carrot and yellow varieties of yam are rich in carotene and potato contains Vitamin C. Tapioca and yam are rich in calcium. Roots and tubers are a poor source of iron, protein and a fair source of B – Vitamins. iii. Other Vegetables : These are a good source of dietary fibre and add variety to the diet. They are a fairly good source of vitamins and minerals. (Eg.) brinjal, ladies finger, cauliflower, cucumber, gourd varieties. 43 FRUITS A fruit is a mature ovary of a flower. The fleshy portion of the pericarp makes up the chief edible portion of the fruit. Fruits can be classified as follows : Berries - Gooseberry, grapes, strawberry. Citrus - Lemon, lime, orange, sweet lime. Drupes - Peach, plums, apricot. Melons - Water melon, musk melon Pomes - Apple, pear. BERRIES : Berries are fruits with layers of pericarp(fruit coat) which are often homogenous, except for the skin on the outside. The pericarp layers are pulpous and juicy, and contain seeds embedded in the pulp mass. The fruits have fragile cell structure that is damaged by rough handling or freezing. CITRUS FRUITS: These fruits belong to the genus Citrus which contains about 16 species of evergreen aromatic shrubs and trees mostly with thorny branches distributed throughout the tropical and subtropical regions of the world. The common citrus fruits are orange, lemon and lime. The bright colour, pleasing flavour and sweetness make them a favourite fruit. They are served as juice and can be eaten raw. DRUPES: Drupes are edible fruits with a thin skin, and juicy flesh enclosing a single seed (Stone). Apricots, cherries, peaches and plums belong to this group. MELONS: Melons belong to the same family as cucumbers (Cucurbitaceae). Melons are commonly eaten raw. Their flesh consists of about 94% water and only 5% sugars. The seeds stripped of their hard coats may be eaten and also yield an edible oil. 44 POMES Pomes are fruits of apple and pear trees. The receptacle, surrounds the ovaries in the flower, enlarges to become edible and juicy, and encloses the cells containing the seeds. Fruits particularly citrus varieties and guava are a good source of vitamin C. Yellow fruits like mango and papaya contain – carotene. Banana is a good source of carbohydrate and hence energy. Fruits are a poor source of protein and fat with the exception of avacado. Fruits also contain fibre and minerals such as sodium, potassium and magnesium. They are not a good source of calcium. Dry fruits, seethaphal and watermelon contribute appreciable amounts of iron. 5.3 PIGMENTS AND FLAVOUR COMPOUNDS Chlorophyll : Chlorophyll is the green pigment of leafy vegetables and other green coloured vegetables Carotenoids: Carotenoids are the yellow, orange, red fat soluble pigments distributed in nature. They are divided into three groups viz. carotenes present in carrot, green leafy vegetables and other fruits, lycopenes present in tomatoes and xanthophylls present in yellow fruits. Pigments that contain the phenolic group include anthocyanin, anthoxanthin, leucoanthoxanthin, catechin, quinones and betalins. The first four groups are collectively known as “Flavanoids” Anthocyanin : They are a group of reddish water-soluble pigments occurring in many fruits and vegetables. Cherries, red apples, pomegranates have their colour appeal due to anthocyanins. Anthoxanthins : They are colourless white to yellow pigments that give colour to cauliflower, onions, spinach or other leafy vegetables. In green leafy vegetables the colour is masked by chlorophyll. 45 Leucoanthoxanthins : They are colourless and contribute to the puckeriness or astringency of some foods, such as apple and olives. They also play an important role in the enzymatic browning of fruits. Catechins : They are pigments that are involved in enzymatic browning. Betalins : They are the red water soluble pigments found in beetroot and berries. Quinone : The yellow pigment juglone is a quinone present in walnut. Mangiferin : This is the yellow pigment belonging to the xanthone group. It is found in mangoes. Tannins : They are complex mixtures of polymeric polyphenols. The appearance of tannins ranges from colourless to yellow or brown. Tannins contribute to the astringency of foods and also to enzymatic browning. Flavour Compounds : The flavour of fruits and vegetables are extremely important to their acceptance in the diet. The overall flavour impression is the result of the tastes perceived by the taste buds in the mouth and the aromatic compounds detected by the epithelium in the olfactory organ in the nose. In fruits and vegetables, this means that sugars, acids, salts and bitter quinine-like compounds are tasted while the food is chewed in the mouth. Sweetness may result from the presence of glucose, galactose, fructose, ribose, arabinose and xylose. 46 All fruits and vegetables contain a small amount of salt, which is detected in the overall taste impressions contributing to flavour. The natural flavours of vegetables are due to mixtures of aldehydes, alcohol, ketones, organic acids and sulphur compounds. Some fruits and vegetables have an astringent taste attributed to phenolic compounds or tannins. Two types of vegetables viz., vegetables belonging to the Allium and Cruciferae families have strong flavours resulting from the presence of various sulphur containing compounds. Allium is the genus that includes onions and garlic. Members of the family cruciferae, which include broccoli, cabbage, turnips and cauliflower also contain prominent sulphur compounds. They are described as strong flavoured vegetables. Vegetables of the onion family are usually strong flavoured in the raw state and tend to lose some of the strong flavours when cooked in water. Onions contain sulphur compounds that are acted upon by enzymes in the tissues when the vegetable is peeled or cut to eventually produce the volatile sulphur compounds that irritate the eyes and give biting and burning sensations on the tongue. Vegetables of the cabbage family (cauliflower, cabbage, knolkhol) are relatively mild when raw but develop strong flavours when overcooked or improperly cooked. An amino acid s-methyl l-cysteine sulphoxide is also present in raw cabbage and appears to be a precursor of cooked cabbage flavour. 5.4 PECTIN – ROLE IN GEL FORMATION Pectin is the term designated to those water-soluble pectinic acids of varying methyl ester content. They are in between cell walls in soft tissues of most plants acting as cementing substances. In general it is the pulp and not the juice of fruits that contain pectin. Apples contain abundant pectin in their cores and 47 skin. In the preparation of jams, the cores and skins are cooked with the pulp for pectin extraction. In citrus fruits, the pectin is chiefly in the white part of the rind. Other sources are sunflower seeds, guava and peels of mango and orange. Heat is essential to extract the pectin. The usual way to extract the pectin from fruit is to heat the fruit in a small amount of water. Apples are cut into small pieces or ground with skin or core left intact and cooked to extract the maximum amount of pectin. Guavas are sliced thin and cooked with water to extract pectin. Some points to be remembered for extracting pectin The maximum quantity of pectin is extracted in an acid solute. If fruits are rich in pectin but low in acidity, acidifying the solution before cooking increases the viscosity of the extraction. Cooked extractions contain more pectin than raw juices. Short periods of cooking (usually 10-20 minutes) yield extractions of better jellying power than does long boiling. The role of pectin in gel formation The formation of a firm jelly takes place only when pectin, acid and sugar and water are in definite proportions. When sugar is added to the pectin solution, it acts as a dehydrating agent and destabilizes the pectin-water equilibrium and the pectin conglomerates forming a network of insoluble fibres. Large amounts of sugar solution can be held in this mesh- like structure. The strength of the jelly depends on the structure of fibres, their continuity and rigidity. The continuity of the network depends upon the amount of pectin present in the system and the firmness depends on sugar concentration and acidity. A soft jelly can be obtained by decreasing the amount of sugar. However, the rate of setting is modified by acidity. The 48 fibrils of pectin become tough in the presence of an acid and thus able to hold the sugar solution in the interfibrillar spaces. If the amount of acid is large, the fibrils lose their elasticity and as a result jelly becomes syrupy. 5.5 NEED FOR INCLUSION OF FRUITS AND VEGETABLES IN THE DAYS MENU 1. Fruits and vegetables provide vitamins and minerals required for growth and maintenance of health and are thus termed as protective foods. 2. Roots and tubers provide energy. 3. Vegetables are low in fat and can be used liberally in low calorie diets for weight reduction. 4. Besides providing nutrients they add variety to the diet. They make the diet attractive by their texture, flavour and colour. 5. Fruits and vegetables contain phytochemicals. The term phytochemicals refers to the wide variety of plant compounds naturally produced by plants. They include plant pigments and flavouring substances. Fruits and vegetables with bright colours viz., yellow, orange, red, green, blue, purple contain phytochemicals. Beta-Carotene, Vitamin C and Vitamin E are nutrients that function as antioxidants. An antioxidant is a substance that significantly reduces or prevents oxidation of fatty acids and protein thus preventing cell and tissue damage caused by free radicals in the body. Free radicals are unstable molecules resulting from normal metabolic processes. During these processes oxygen molecules lose an electron, which creates an unstable (molecule) thereby causing oxidative stress. These free radicals attack healthy cells in the body in the hope of finding another electron to stabilize themselves. This process can cause damage to healthy cells. 49 6. Intake of fibrous fruits and vegetables are important as they : give satiety and thereby decrease food intake. help in regulating bowel movement. low in calorie content. reduce blood cholesterol levels. promote chewing and decrease rate of ingestion. 7. Vegetable and fruits are used in the preparation of salads. All vegetable have their own characteristic texture and colour. Vegetables can be grated, diced, cubed, or cut into a variety of shapes to prepare salads. The orange colour of carrots, the pale green of cabbage, the red colour of tomatoes, the green peppers and the white colour of cucumber, all indicate the variety of colours available to make attractive salads. Vegetable used to prepare salads contribute vitamins and minerals to the diet. Vegetable salads are an important means of providing part of the need for fibre. Fruit salad is a colourful, refreshing and light dessert. Pineapple, orange segments, apple cubes, papaya cubes, grapes, bananas, sapotas, mangoes, pomegranates are some of the fruits which can be used in a salad. 5.6 CONSERVATION OF NUTRIENTS IN PREPARATION AND COOKING OF VEGETABLES Loss of nutrients in vegetables begin from preparation onward and is greater during the cooking process. 1. When fruits and vegetables are peeled the vitamins present under the skin may be lost. 2. Nutrients are also lost when the edible leaves of carrot beetroot and outer layer of cabbage are discarded. 3. Vitamin B complex and Vitamin C are water soluble and are lost when the water in which vegetables are cooked is discarded. Sodium, potassium and chlorine are also lost when cooking water is discarded. 50 4. Vitamin C is lost by oxidation due to exposure of air. 5. During dehydration ascorbic acid and carotene are lost. 6. Addition of soda results in heavy loss of B – Vitamins during cooking. Guidelines to minimize nutrient losses during preparation: 1. Wash vegetables before cutting. Soaking or washing time should be reduced to minimize nutrient loss. 2. Cut vegetables into big pieces so that exposure of vitamins to water is less while cooking and washing. 3. Use a vegetable peeler to remove skin as it helps remove only a very thin layer of skin. 4. Use minimum water for cooking. Bring the water to boil and add the vegetables to cook. 5. Cook vegetables by steaming and pressure-cooking to conserve nutrients. 6. Cover the vessel with a lid while cooking as it hastens cooking. 7. Do not use soda while cooking vegetables as it destroys valuable vitamins. 8. Vegetables salads should be prepared just before serving to conserve nutrients. 9. Use acids such as lime juice or vinegar to salads as it prevents loss of Vitamin C since Vitamin C is stable in acid. 5.7 BROWNING When fruits and vegetables such as apple, banana, potato and brinjal are cut, there is a development of brown colour on the surface due to action of enzymes. This is known as enzymatic browning. When the tissue is injured or cut and the cut surface is exposed to air, phenol oxidise enzymes are released at the surface. These act with the polyphenols present in the fruits and oxidises them to orthoquinones, which gives the brown colour to cut tissues. 51 Browning can be prevented by the following methods : 1. Inactivation of polyphenol oxidise by applying heat. 2. Elimination of oxygen by vacuum packing. 3. Change of pH to prevent enzyme action. 4. Dipping of fruits and vegetables in brine and sugar solutions. 5. Use of antioxidants such as ascorbic acid to retard oxidation. QUESTIONS Part-A Fill in the blanks: 1). Roots and tubers are rich in _______ 2). __________ is the green pigment of leafy vegetables. 3). _________ is the pigment present in carrot. 4).The pigment present in tomato is _________. 5)._________ are a group of reddish water soluble pigments occurring in many fruits and vegetables. 6). Anthoxanthins are present in ___________ vegetables. 7).The pigment present in beetroot _________. Part-B Write short answers 1). How are vegetables and fruits classified? 2). List the major nutrients present in fruits 52 3). Highlight the importance of fibre rich fruits and vegetables in the diet. 4). Why does an apple become brown when it is cut? 5). What is browning? How can it be prevented? 6) Write a note on the flavour compound present in vegetable. Part- C Write detailed answers 1. Compare the nutrient content of green leafy vegetables roots and tubers. 2. Justify the need for inclusion of fruits and vegetables on the day’ s menu. 3. How does cooking affect the nutrient content of vegetables? How can it be prevented? 4. Discuss the pigments and flavour compounds present in fruits and vegetables. 53 6. MILK AND MILK PRODUCTS The story of milk goes back to the beginning of civilization itself. Cattle were domesticated even in prehistoric times and milk was one of the most essential of all foods. Milk is one of the most complete single foods available in nature for health and promotion of growth. Milk is the normal secretion of mammary gland of mammals. Its purpose in nature is to provide good nourishment for the young of the particular species producing it. Man has learnt the art of using milk and milk products as a food for his well being and has increased the milk producing function of the animals best adapted as a source of milk for him. The cow is the principle source of milk for human consumption in many part of the world; Other animals as source of milk for human beings are the buffalo, goat, sheep, camel and mare. In India, more milk is obtained from the buffalo than the cow. Some amount of goat milk is also consumed. 6.1 NUTRITIVE VALUE OF MILK Milk is a complex fluid containing protein, fat, carbohydrate, vitamins and minrals. The main protein in milk is casein and it constitutes 3.0 - 3.5 percent of milk. The fat content of milk varies from 3.5 percent in cow’ s milk to about 8.0 percent in buffalo’ s milk. Fat is present in the form of fine globules varying in diameter from 1 to 10 µm (micrometers).Milk also contains phospholipids and cholesterol. Lactose is the sugar present in milk. The important minerals in milk are calcium, phosphorus, sodium and potassium. Milk is an excellent source of riboflavin and a good source of Vitamin A. However, milk is a poor source of iron and ascorbic acid. The small amount of iron present is bio available. 54 6.2 TYPES OF PROCESSED MILK Raw milk is processed into the following types of milk. 1. Skim Milk: Skim milk is whole milk from which fat has been removed by a cream separator. The quantity of fat is usually 0.05 to 0.1 percent. It contains all other milk nutrients, except Vitamin A and D, but can be fortified by the addition of these vitamins. 2. Toned Milk : Toned milk is prepared by using milk reconstituted from skim milk powder. Skimmed milk is prepared by removing fat from milk in a cream separator. The skimmed milk is then mechanically dried to give skim milk powder. It is mixed with buffalo milk containing 7 percent fat. The fat content of toned milk should be less than 3 percent. 3. Standardised Milk: In standardised milk the fat content is maintained at 4.5 percent and soluble non-fat is 8.5 percent. It is prepared from a mixture of buffalo milk and skim milk. 4. Homogenised Milk: Homogenisation is a mechanical process that reduces the size of fat globules by forcing milk through small apertures under pressure and velocity. When milk is homogenised, the average size of the globule will be 2 micrometers. The decrease in the size of fat globules increases their number and surface area. The newly formed fat droplets brings about stabilisation of the milk emulsion and thus prevents rising of the cream. Homogenised milk has a creamier texture, bland flavour and whiter appearance. 5. Evaporated Milk: It is made by evaporating more than half the water from milk under vacuum, at a temperature of 74° C - 77° C. It is then fortified with vitamin D, homogenised and filled into cans 55 and sterilized at a temperature of 118° C for 15 minutes and cooled. The treatment employed lends a brown colour and characteristic flavour owing to the reaction between sugar and protein. 6. Condensed Milk: It is obtained when whole milk is concentrated to about one-third of its original volume and has about 15 percent sugar added to it. The preparation of condensed milk involves (i) filtration and pasteurization of milk, (ii) preheating and evaporation, (iii) addition of sterilised sugar syrup, (iv) homogenisation. 7. Flavoured Milk : It is the milk prepared by the addition of flavour such as rose, pista, badam, cardamom etc. to pasteurised whole milk. 8. Milk Powder: Milk powder is prepared by dehydrating whole milk in drum driers or spray driers. In the case of drum or roller drying, the milk is filtered, pasteurized, homogenised and then fed into roller driers which are internally heated with steam. The dried milk is obtained as a thin sheet and is powdered. In spray drying, the homogenised milk is blown as a fine spray into a pre-heated vacuum chamber resulting in fine dry powder. The milk powder is collected, cooled and packed. 6.3 PHYSICAL PROPERTIES OF MILK Acidity : Milk has a pH of about 6.5 to 6.7. The salts of the minerals – calcium, phosphorus, sodium and potassium help to maintain this pH level. Viscosity : The viscosity of milk is affected by temperature, amount and nature of dispersion of protein and fat, acidity and the effects of various enzymes and bacteria. Homogenization increases the viscosity of milk. 56 Freezing Point : The freezing point of milk is –0.55° C. Boiling Point : Milk boils at 100.2° C. 6.4 PASTEURISATION OF MILK Milk is a favourable medium for bacterial growth. Pasteurisation destroys all pathogenic bacteria, including those causing typhoid, tuberculosis, diphtheria as well as yeasts and moulds. Pasteurization is a process which consists of heating milk to a certain temperature for a definite time to ensure destruction of harmful bacteria. There are three methods of pasteurisation. a) Holding method or Batch process : In this method, milk is held at 62.8° C for 30 minutes and then rapidly cooled to prevent multiplication of surviving bacteria. b) High temperature short time (HTST) method or continuous process : Milk is heated to 71.7° C for not less than 15 seconds. c) Ultra High temperature method : Milk is heated to a temperature of 93.4° C for 3 seconds. Advantages of Pasteurization During pasteurization the nutritive value of milk is not altered to a great extent because the temperature employed is not high and cooking time is short. However, there is a slight decrease in heat labile vitamin such as thiamine and ascorbic acid. Proteins are denatured only slightly and minerals are not appreciably precipitated. It does not produce an unpleasant cooked flavour. Shelf life of milk is increased due to a marked decrease in the total bacterial count. Harmful pathogens especially TB bacteria are destroyed. 57 It inactivates enzymes such as phosphatase and lipase in milk which adversely affect the quality of milk. 6.5 MILK PRODUCTS Khoa: Khoa is prepared by evaporating whole milk in an open cast iron pan with continuous stirring until it is semi-solid. It is used extensively in the preparation of Indian sweets. Cream : Cream is the fat of milk and is used in the preparation of sweets. It is made by simmering large quantities of milk until a thick layer of milk fat and coagulated protein form on the surface. It can be consumed with or without the addition of sugar. Butter : Butter is obtained from cream by churning. When cream is churned, the fat globules are destabilised and coalesce until the milk separates into two phases – viz., the butter and the aqueous phase. Butter is removed and washed. Butter is used as a cooking medium in many Indian recipes. It is one of the main ingredients in cakes, biscuits, icing and bread. Ghee : Ghee is butter oil. It is prepared by melting butter and separating the moisture from butter by heating. It is used in preparing Indian sweets, savouries, curries and variety rice like pulav and biriyani. Paneer : Paneer is a soft cheese prepared by addition of lemon juice or citric acid to hot milk and precipitating the casein. The liquid released in this process is known as whey and the resultant curd is tied in a muslin cloth and hung for a day to squeeze any liquid present in it. The soft cheese (paneer) that is obtained is used in Indian gravies and pulavs. It is a very good source of protein. 58 Cheese : It involves the curdling of milk with enzyme rennet under microbially controlled condition. Milk is held at about 27° C in vats and a lactic acid culture is added. When the milk gets acidic, rennet is added to it and the milk is allowed to coagulate. The curd formed is cut and heated to about 37° C with constant stirring to remove the whey. The whey is drained. Salt is mixed with the curd and it is pressed to remove further amount of whey. The cheese formed is coated with paraffin to prevent loss of moisture. The paraffined cheese is allowed to ripen for three to six months at temperatures between 45° to 60° C. Cheese is a concentrated source of protein. Curd : Curd is prepared by heating milk to about 50° C. A teaspoon of curd (starter) from an earlier batch of curd is added and is mixed thoroughly. The lactic acid bacteria present in the starter curdles the milk. The bacteria breaks down lactose to lactic acid thereby increasing the acidity of milk. When the pH reaches 4.6, the milk protein casein coagulates as curd. The optimum temperature for the formation of curd is 35° - 40° C and the time needed for curd formation is 8 – 12 hours depending on the atmospheric temperature. Curd is used as a dressing on salads made from fresh vegetables and combines well with plain cooked rice. Yoghurt : This is a coagulated milk product with curd like consistency. It is made from partially skimmed or whole milk and it has a slightly acidic flavour. In the production of yoghurt, a mixed culture of Lactobacillus bulgaricus, Streptococcus thermophilus and Lactobacillus acidophilus is added to pasteurised milk and incubated at 42° C to 46° C. 59 6.6 ROLE OF MILK AND MILK PRODUCTS IN COOKERY It contributes to the nutritive value of the diet, e.g., milk shakes, plain milk, flavoured milk, cheese toast. Milk adds taste and flavour to the product e.g., payasam, tea, coffee. It acts as a thickening agent along with starch e.g., white sauce or cream soups. Milk is also used in desserts, e.g., ice-cream, puddings Curd or buttermilk is used as a leavening agent and to improve the texture, e.g., dhokla. Curd is used as a marinating agent, e.g., marinating chicken and meat. Curd is used as a souring agent, e.g., rava dosa, dry curd chillies. Khoa is used as a binding agent, e.g., carrot halwa. Cheese is used as garnishing agent. Salted butter milk is used for quenching thirst. QUESTIONS Part-A Fill in the blanks: 1). The main protein present in milk is known as ______________ 2). ____________ is the sugar present in milk. 3). The fat content of toned milk is _____________ percent. 4). The process of breaking fat globules is known as __________. 5). The pH of milk is ________________. 6). The boiling point of milk is ___________ and its freezing point is ________________. 7).When fat is removed from whole milk, the resultant product 60 is known as ______________. 8) ______________ is prepared by evaporating whole milk in an open cast iron pan. 9). _____________ is obtained by melting butter. 10).In the preparation of cheese, milk is curdled using ____________. Part-B Write short answers: 1).What are the nutrients present in milk? 2).Differentiate toned milk and homogenised milk. 3).Write a brief note on the physical properties of milk. 4).Write a short note on homogenisation. Highlight its advantages. Part- C Write detailed answers: 1). Why is pasteurization and homogenization carried out in milk? Highlight its advantages. 2). Give a detailed account on the various milk products prepared from milk. 3). Discuss the role of milk and milk product in cookery. 61 7. FLESH FOODS AND EGG 7.1 NUTRITIVE VALUE AND SELECTION CRITERIA OF MEAT, POULTRY, EGG AND FISH Meat : Meat refers to the flesh of warm blooded, four legged animals chiefly cattle, sheep and pigs. Meat of sheep which is under 12 months age is sold as lamb. After the age of 12months, it is called mutton. Pork is the meat of swine (pig) slaughtered between the age 5 and 12 months. Veal is the meat of cattle that is slaughtered 3 to 14 weeks after birth. If slaughtered between 14 to 52 weeks the meat is called calf. Meat obtained from cattle slaughtered one year after birth is called beef. Meat is a very good source of protein. The average protein content of meat varies from 16 – 25 percent. The amino acid pattern of meat protein is of outstanding nutritive value. The fat content of meat varies from 5 – 40 percent. Depending on the type, breed and age of the animal, fat is distributed throughout meat in small particles of large masses. Fat deposited uniformly in small sheets in the connective tissue within the muscle is called “marbling”. This contributes tenderness and flavour to the meat. Meat fats are rich in saturated fatty acids. The cholesterol content of meat is 75 mg / 100 gm. Carbohydrate is found in small quantities and present in the form of glycogen and glucose. Meat is a good source of iron, zinc and phosphorpus. It also contains sodium and potassium. It is an excellent source of B-complex vitamin particularly B12 which is absent in plant foods. Liver is an excellent source of iron and vitamin-A. 62 Changes in Meat : After slaughtering, the lean tissues undergo a series of complex physical and chemical changes. As a result muscles loose their soft pliable nature and become rigid, stiff and inflexible. This is termed as “rigor mortis”. Stiff muscle starts to soften and becomes tender when it is held in a cold room temperature between 0°C to 20°C for 1 – 4 weeks. This is known as “ripening” or “ageing”. During ageing the humidity of the room is to be controlled. Tenderness of meat can also be obtained by the use of mechanical methods such as pounding, cutting and grinding which break muscle fibre. Addition of salt, vinegar, lime juice and enzymes viz., papain, bromelin and ficin also help in tenderising meat. Changes that occur during cooking: On heating, the red pigment turns brown due to the denaturation of protein pigment. Heat treatment also brings about inactivation of enzymes and denaturation of proteins, which makes meat tougher. Hence, adopting correct cooking methods, time and temperature will result in a well- cooked product. Heating results in release of volatile compounds from both fat and lean meat which contributes to the flavour and taste of cooked meat. Heating melts meat fat which increases palatability of meat when eaten warm. There is loss of water on heating which does not change the nutritive value but may affect juiciness and bring about shrinkage in volume and weight. Minerals like calcium may be lost in meat dripping due to the dissolution of calcium from bones. There is loss of B-vitamins also. 63 Poultry: The term poultry refers to domestic fowls reared for their flesh and egg. It includes chicken, duck, geese, turkey, pigeon etc. Poultry meat has a high protein content varying from 18 to 25 percent. It contains all the essential amino acids required for body building. Fat content of poultry is influenced by age and species of the bird. Young birds have little fat content. Chicken fat is unsaturated and is therefore better than the fat of red meat. Poultry flesh is a good source of B-vitamin and minerals. Egg : The term egg mainly refers to the egg of hen and duck. An average egg weighs 50 gms. approximately and is composed of the shell, egg white and yolk. The weight is distributed in the different parts as follows. TABLE – 7 A Percentage composition of egg Part Weight% Shell 8 – 11 White 55 – 61 Yolk 27 - 32 Egg is a rich source of protein and lipids. Egg protein is of high quality as compared to any dietary protein and therefore is used as a standard for evaluating the protein quality of other foods. The nutrient composition of egg white and yolk differ considerably and is represented in the following table. TABLE – 7 B Percentage nutrient composition of egg white and yolk Nutrient Egg white Egg yolk Water 88.0 % 48.0 % Protein 11.0 % 17.5 % Fat 0.2 % 22.5 % Mineral 0.8 % 2.0 % 64 Vitamin and minerals in Egg: Egg yolk is rich in vitamin-A. Thiamin and riboflavin are present in appreciable amounts. Calcium is present in the yolk in small amounts. Phosphorus is abundant in the yolk. Eggs are an important source of bioavailable iron and a fair source of sodium, magnesium chlorine, potassium and sulphur. Fish: Fishes are classified as shell fish and fin fish. The nutrient composition of fish of a given species varies depending on the season of year and maturity. However most fish contain 15 – 24 percent protein, 0.1 – 22 percent fat and 0.8 – 2 percent minerals. Fish proteins are easily digestable and are of high biological value. The fat content is influenced by the species, feeding habits and maturity of fish. Glycogen is present in fish but is in lesser quantities than meat. Fish oils are an excellent source of vitamin A and D. They are a good source of thiamin, riboflavin and niacin. Small fishes that can be eaten with bones contribute a significant amount of calcium. Ocean fish are a rich source of iodine. Oysters are an excellent source of copper. Fishes contain omega – 3 polyunsaturated fatty acids. These acids are found to prevent the degeneration diseases of the heart. SELECTION CRITERIA: Meat: Veal or the meat of calf is pale pink and firm. The meat is soft and flabby and the cut surface is moist. The bone is pinkish white with a small quantity of blood. Fat is not seen. In the case of lamb, flesh of young animals below 12 months of age, the meat is pinkish red, fine grained and velvetty. The bones are porous and reddish. Good quality mutton is deep red in colour with a smooth covering of fat. The bone is hard and white. 65 Poor quality meats have darker flesh and the grain is coarse and fibrous. Fat layers are heavy and have a strong flavour. Poultry : Young birds (below 9 months of age) have a tender flesh and are more suitable for cooking. Signs of a young bird : The feathers especially the quills on the wings should be easy to pull. No long hair on the body. Skin should be white or clean and smooth. Feet should be supple with smooth even over-lapping scales. Signs which show that a bird is fresh : Feathers – light and fluffy. Eyes – prominent and clean No unpleasant smell Feet moist and not stiff and dry. Skin – clear with no dark or greenish tinge. Egg: The shell should be clean and should not be broken. Fresh eggs have a small air cell. This can be detected by holding the egg against light. Yolk should be in the centre without any dark spots when observed against light. Good quality egg will sink when immersed in water. Poor quality eggs will float due to the enlarged air cell and loss of moisture. Fish: The following points should be borne in mind while selecting fish : i) Eyes should be bright and not sunken. ii) Gills should be red. 66 iii) The tail should be stiff and scales firmly attached to the skin. iv) The flesh should be firm and not flabby. v) There should be no unpleasant odour. vi) To test a cut piece, press down with a finger and if an impression is left then the fish is stale. vii) Any tendency for the raw flesh to come away from the bone is a dangerous sign. 7.2 USE OF EGG IN COOKERY As a Thickening Agent : Egg proteins coagulate on heating. The coagulation of protein is accompanied by binding of moisture and increase in viscosity. Therefore eggs can be used as thickening agents. As a Binding Agent : Egg protein coagulate between 65 and 70° C and help to hold shape of the products such as cutlets in which it is used. As a Leavening Agent : Eggs when beaten, form elastic films which can trap air. This air expands during baking and gives a fluffy spongy product. As a Emulsifying Agent : Besides protein, egg contains phospholids such as lecithin which are known for their emulsifying quality. Hence egg can be used an excellent emulsifying agent in products such as mayonnaise as it is able to stabilise the oil in water dispersion. As a Flavouring and Colouring Agent : Egg is used in food mixtures to contribute flavour and colour to products such as cakes and pudding As a Clarifying Agent: Egg helps in the preparation of clear soups. When a small amount of egg white is added to the liquid and heated, the 67 egg albumin coagulates and carries along with it suspended particles. On allowing it to settle, a clear soup is obtained. As a Garnishing Agent : Hard boiled eggs are diced and are used to garnish dishes like biryani. As an Enriching Agent : Eggs are used to enhance the nutritive value of various preparations.

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