Preface Food has never commanded more stories in the press or on television than it has in current decade. Public concerns about personal health and the environment have promoted the newsworthy nature of food. In particular, the merits of a healthy diet have been translated into emphasis on reducing the intake of fats & sugars while increasing the intake of fruits, vegetables and cereal products. The food industry has responded by developing many products to make it easier for consumers to follow dietary guidelines. Biotechno-logists have been providing most of possible new directions to enhance the food supply. People in the media have added to the excitement, unfortunately not always with accurate message to consumers. The challenge is to keep moving toward a safe, adequate and pleasing supply of food that meets the true needs of consumers. This book provides a sound scientific knowledge in food science. It has been written to meet the needs of students in Indian Universities perusing courses in foods, nutrition and allied courses; at the undergraduate and postgraduate levels. The book covers all the necessary topics.

SENSORY EVALUATION OF FOOD When the quality of a food is judged or evaluated by the senses (taste, smell, sight, touch and hearing), it is said to be a sensory evaluation. Since food is prepared for the primary purpose of being eaten and enjoyed through the senses, sensory evaluation is most appropriate. No machine has yet been devised that can totally substitute for the human senses in evaluating the quality of human food. However, the human instrument used in sensory evaluation is very complex and many problems need to be managed as data are collected and analysed. Computers are generally used to analyse data from sensory evaluations and may also be used to collect information firsthand. Flavour perceptions are difficult to characterise verbally, for example, think about how a strawberry tastes, then try to describe it some one else. In food research small groups of trained individuals called juding panels or sensory panels are commonly used to determine differences among food samples. These panels often consist of from 5 to 15 individuals who have had training and experience in testing the particular food products being evaluated.

INTRODUCTION COLLOIDS :  The word colloids has actually been derived from Greek language where it means glue like. The science of colloids was founded about 1861 when Thomas Graham published a summary of his work on the diffusion of substances in solution. He classified substances into two groups, viz: crystalloids and colloids, depending on their ability to diffuse through parchment membrane. According to Graham, crystalloids readily passed through parchment membranes while colloids did not. According to modern concept, colloidal solution contain substances whose molecular aggregates possess a diameter greater than 1 mu  and less than 100 mu. If the particle size is greater than 100 mu, a suspension is obtained (Table 1).

CARBOHYDRATES AND SUGARS Carbohydrates which include sugars and starches are among the most important of the food stuffs as well as the simplest of organic foods. They may be divided into three groups. Group – I Monosaccharides  : These are simple sugars that cannot be split into any simpler forms. The principal ones are glucose or dextrose, fructose and galactose. Glucose sometimes known as dextrose or grape sugar is found widely distributed in nature, especially in fruits and vegetables, and is one of the main constuents of honey. It is in the form of glucose that sugar appears in the blood and is being burned continuously to produce energy. A certain amount of surplus glucose is absorbed from the digestive tract and stored in the liver as glycogen, which can be converted back into glucose when the need for more fuel arises. In the presence of yeasts, glucose undergoes fermentation and changes into alcohol.

STARCH : Starch is a complex carbohydrate that has been cursed by dieters in years past, but that now is praised by nutritionists as a particularly healthful source of energy. In food preparation at home starch is a very important as a thickening agent. However starch is but one of several polysaccharides that are used as thickners in the food industry. STRUCTURE : Although starch is the name used by nutritionists this complex carbohydrate actually consists of two fractions amylose and amylopectin. The two fractions occur together in starch from most sources so the overall behaviour of starch is determined in large measure by the relative amounts of amylose and amylopectin. Each of the fraction has unique properties that contribute to the functionality of starch from various plant sources.

Milk is the one food for which there seems to be no adequate substitute. It constitutes almost the entire diet for the young of all mammals. Each species produces milk that is especially adapted to the growth of its own young, but milk from one species may be used as food for others. Since animals were domesticated centuries ago, the milk from various species such as cow, buffalo, goat and camel, has been used in the diets of people throughout the world. Only cows milk is of commercial importance in the United States, although small amounts of goat’s milk are sold. Whole cow’s milk is approximately 88 percent water, 5 percent carbohydrate, 3.5 percent protein and 3.3 percent fat. Its nutrient content varies from species to species, from breed to breed, seasonally and even from the beginning of the milking to the end of the process. In the United States it is cow’s milk that is used commonly as a beverage and in food preparation. Therefore the milk discussed throughout this chapter is cow’s milk.

INTRODUCTION EGGS : Eggs and egg products constitute an important part of family meals. The economic importance of the egg to agriculture and industry, its multiple uses in the preparation of many food products, and its excellent nutritive value have stimulated scientific scrutiny into the nature of the egg. STRUCTURE : The chief parts of the egg are the yolk, the albumin (the white), and the shell and the shell membranes. The yolk is more complex structurally than may be thought at first glance. At the very center is a light coloured structure called the white yolk. The vitelline membrane serves as the enclosure or sac for the yolk. The strength of this membrane is important when yolks and whites needs to be separated in cookery. Two important rather twisted membraneous structures extend from opposite sides of the yolk into the white.

INTRODUCTION Vegetables and fruits have many similarities with respect to their composition, methods of cultivation and harvesting, storage properties and processing. In fact many vegetables are considered fruits in the true botanical sense. But the difference between the two is that vegetables are derived from various parts of plants e.g. roots, leaves, stems, buds and so on whereas, fruits are the mature ovaries of plants with their seeds. The edible position of most fruits is the freshly part of the pericap or vessel surrounding the seeds. The other difference between the two is that those plant items that are generally eaten with the main course of a meal are often considered to be vegetables, whereas those that are eaten alone or as a dessert are considered as fruits. This is the distinction made by food processors, certain marketing laws, and the consuming publics.

Fats are obtained from both animal and vegetable sources. The principal animal fats are cream, butter, egg yolk, the fat of beef, mutton, pork, bone marrow, chicken fat, and codliver oil. Vegetable fats are those derived from fruits and seeds of plant, as olive oil, cottonsed oil, corn oil, peanut oil, soyabean oil and nut oils. COMPOSITION AND NUTRITIVE VALUE OF FATS Fats and oils, the most concentrated of fuel foods, were the first of the organic compounds or foods to have their composition determined. They are made up of same three elements which go to produce the carbohydrates, but the oxygen is less in proportion to the carbon. This explains the fact that fat yields more energy per gram than carbohydrates do.

INTRODUCTION Pulses are edible fruits or seeds of food bearing plants belonging to the family of the leguminosae. The major pulses which find important place in our diet are redgram dhal, bengal gram dhal, black gram dhal, green gram dhal and masoor dhal. Some are used as whole grams cow pea, rajmah and dry peas also belong to leguminous family. Legumes not only have dietary values but also play an important role in maintaining or even improving soil fertility through their ability to fix atomospheric nitrogen.

INTRODUCTION Many people confuse fortification with the term enrichment. There is a big difference in between these two terms. Fortification means the addition of those ingredients not normally found in a food and it is added to achieve a particular dietary purpose. Lysine may be added to corn products to increase the biological value of the protein. Salt may be iodised to prevent the occurrence of goiter. Breakfast cereals may be fortified with an array of vitamins and minerals to ensure a completely balanced nutritional meal. In enrichment, the amounts added are designed to meet specific legal standards of minimum and maximum levels of nutrients. It is recognised that in the processing of cereal products that the removal of bran and germ causes a large portion of the vitamins and minerals naturally found in the product to be lost. During World War II an effort was made to correct this deficiency by government endorsement of the enrichment of bread, flour, and cornmeal. Wheat flour, cornmeal, corn grits, bread, ready to eat and uncooked cereals, and macroni products have been enriched with thiamine, ribo-flavin, niacin, iron and in some cases, calcium and vitamin D. W.H.O. has defined food fortification as “a process where by nutrients are added to foods to maintain or improve the quality of the diet of a group, community or population”.

INTRODUCTION Meat is the flesh of animals that is used for food and consists of muscle, fat and bone. If the muscle which is commonly known as the lean meat, is examined under the microscope, it is seen to be made up of bundles of fibers held together by a thin membrane called connective tissue. Further study reveals that these fibers are in readily hollow tubes that vary in length in different animals and in different muscles in the same animals that are filled with a fluid, sometimes called muscle juice, which is known to contain protein, minerals and extractives. The forms of protein in the muscles are myosin (a globulin) and myogen (an albumen) and in addition, on red meats, hemoglobin.

INTRODUCTION Adulteration of food consists of substituting it wholly or in part by any cheaper or inferior substance or of removing any of its constituents, wholly or in part, which affects adversely the nature, substance or quality of the food. According to the Indian Prevention of Food Adulteration Act (PFA) 1954, any ingredient which, when present in food, is injurious to health is an adulterant. Thus, according to the PFA definition, many of the food contaminants discussed in the previous section are adulterants and come under the purview of food adulteration. Adulteration of foods was practised even in ancient times. It was not a serious problem then because business was on a small scale and the transactions involved a large measure of personal accountability. Later, with the increased centralization of food processing and distribution, and corresponding decline in personal accountability, intentional adulteration of food increased. Even in the early nineteenth century, many adulterants were used in articles like pepper, essential oils, vinegar, beverages (coffee, tea, beer, wines), butter, bread, etc. In recent years adulteration of foods has become a serious problem the world over. In western countries there is a rising concern over the safety of the food supply and many remedial actions, both voluntary and enforced, have been taken.