PRINCIPLES OF FOOD SCIENCE BHM117 - PRINCIPLES OF FOOD SCIENCE HOURS ALLOTED: 30 MAXIMUM MARKS: 100 S.No. Topic Hours Weight age 01 Definition and scope of food science and 02 5% It’s inter-relationship with food chemistry, food microbiology and food processing. 02 CARBOHYDRATES 04 15% A. Introduction B. Effect of cooking (gelatinisation and retrogradation) C. Factors affecting texture of carbohydrates (Stiffness of CHO gel & dextrinization D. Uses of carbohydrates in food preparations 03 FAT & OILS 05 20% A. Classification (based on the origin and degree of saturation) B. Autoxidation (factors and prevention measures) C. Flavour reversion D. Refining, Hydrogenation & winterisation E. Effect of heating on fats & oils with respect to smoke point F. Commercial uses of fats (with emphasis on shortening value of different fats) 04 PROTEINS 04 15% A. Basic structure and properties B. Type of proteins based on their origin (plant/animal) C. Effect of heat on proteins (Denaturation, coagulation) D. Functional properties of proteins (Gelation, Emulsification, IHM –BANGALORE [2014] Page 1 PRINCIPLES OF FOOD SCIENCE Foamability, Viscosity) E. Commercial uses of proteins in different food preparations(like Egg gels, Gelatin gels, Cakes, Confectionary items, Meringues, Souffles, Custards, Soups, Curries etc.) 05 FOOD PROCESSING 03 10% A. Definition B. Objectives C. Types of treatment D. Effect of factors like heat, acid, alkali on food constituents 06 EVALUATION OF FOOD 03 10% A. Objectives B. Sensory assessment of food quality C. Methods D. Introduction to proximate analysis of Food constituents E. Rheological aspects of food 07 EMULSIONS 03 10% A. Theory of emulsification B. Types of emulsions C. Emulsifying agents D. Role of emulsifying agents in food emulsions 08 COLLOIDS 02 5% Definition IHM –BANGALORE [2014] Page 2 PRINCIPLES OF FOOD SCIENCE Application of colloid systems in food preparation 09 FLAVOUR 02 5% Definition Description of food flavours (tea, coffee, wine, meat, fish spices 10 BROWNING 02 5% Types (enzymatic and non-enzymatic) Role in food preparation Prevention of undesirable browning TOTAL 30 100% Definition and scope of food science Food Science Food Science: The study of food science involves understanding the nature, composition and behavior of food materials under varying conditions of storage, processing and use. Thus, it helps us to find answers to questions such as what is food, what happens to it when it is stored, processed, preserved, cooked and what determines its acceptability. Food science embraces many disciplines. Chemical and biochemical methods are used to determine food composition. Knowledge of food composition helps us to use food intelligently to fulfill our nutritional needs. Retention of food quality and preservation of foods are based on food microbiology. The changes that occur in foods during preparation such as volume and texture are physical ones. Study of food acceptability is based on the understanding of socio cultural background. The principles of economics help us to manage food budget efficiently. Thus the basic sciences of physics, chemistry and biology are all involved as also the sciences of biochemistry and microbiology. In addition, one needs understanding of social sciences such as psychology, sociology and economics. Yet food science is more than the sum of these separate disciplines, because it is a subject with its own character. There has been a tremendous increase in our population in the last twenty years. The gains of “Green Revolution” and “White Revolution” have been nullified in the process. The per capita availability of food has decreased in this period. There is an urgent need to conserve foods produced by reducing post-harvest losses to derive maximum benefit from IHM –BANGALORE [2014] Page 3 PRINCIPLES OF FOOD SCIENCE foods produced. In practice, it means we must utilize all edible parts of plant and animal foods and avoid wastage of food, both at personal and institutional level. Effect of Preparation and Processing on Food Components A number of changes occur in the food components as a result of preparation. It is necessary to understand and manipulate the changes to obtain an acceptable food product. The major constituents of food are carbohydrates, proteins, fats and their derivatives and water. In addition, a number of inorganic mineral components and a diverse group of organic substances are present in very small amounts in foods. These include pigments, flavour components, vitamins, acids, enzymes, etc. Let us consider their properties and the changes that occur in these components during handling, cooking and processing. Carbohydrates Starch, sugars, pectins, gums, celluloses and hemi-celluloses are the important carbohydrates found in food. Starches are the major component of cereals, millets, dals, roots, tubers and sago. Starches are bland in taste, not readily soluble in cold water but absorb water when soaked in hot water. When starch granules are added to cold water, a temporary suspension is formed, the starch tends to settle out as soon as the mixture is allowed to stand. When dry starch is mixed with warm or hot water, the part which comes in contact with water becomes sticky and the starch granules cling together in lumps. Heating does not help to separate the granules, because once formed the lumps stay intact. If one of these lumps is broken open, raw starch is found inside. Lump formation can be prevented by mixing starch with a little cold water before introducing it into the hot water; roasting a little before addition of hot water or addition of a little fat, helps to separate the starch granules and allows them to gelatinise separately. The starches take up water, swell and burst on cooking. When a starch and water mixture is heated, it becomes translucent and forms a paste. This change is accompanied by a change IHM –BANGALORE [2014] Page 4 PRINCIPLES OF FOOD SCIENCE in viscosity. This property is used when starch is used as a thickener in soups, starch puddings and other preparations. A gel is formed at a higher concentration of starch, e.g., puddings. The water is held in a physical bond by the starch. The change in texture, colour and physical state, which occurs when starch is heated in water,is known as gelatinisation of starch. In roots and tubers, the presence of starch, which absorbs the water during cooking, results in retention of size. Sugars About 5-11 per cent are present in ripe fruits, malted beverages and in milk. Sucrose, the sugar we use in food preparations is one of the pure, manufactured (extracted) foods we use daily. It is manufactured from sugarcane or sugar beet. Sugar is sweet and is usually used in foods for its sweetening power. Sugar dissolves in water and when heated this solution easily forms a syrup. When the solution is supersaturated and cooled, crystallisation occurs. This is the process used to prepare sweets such as laddus, candies etc. When a high concentration of sugar is used, it acts as a preservative by binding moisture, e.g., preserves such as murrabbas, jams and jellies. In the presence of acids, the sugar (sucrose) is partially hydrolysed to form glucose and fructose, which is known as invert sugar, which is more soluble than sucrose. If sugar is heated beyond its melting point it caramelises or browns. The caramel formed has a bitter, astringent flavour. Sugars are readily fermented by microorganisms, thus causing spoilage of food products containing it. Pectins and gums are responsible for holding the plant cells together. These are found in fruits and vegetables in a very small amount. Pectins and gums form colloidal solution when extracted in hot water and contribute to the viscosity of the product to which they are added. Therefore, these are used as thickeners and stabilisers in food preparation and processing. Pectins form gels in the presence of an appropriate amount of sugar and acid, e.g., fruit jellies. Amla, guava, citrus fruits, papaya and apples contain pectin as soluble fibre. These fruits can be used to make fruit jellies. It is reported that pectin can lower total cholesterol and low-density lipoproteins in the blood. Celluloses and hemicelluloses, the fibrous parts of vegetables and fruits are not soluble in cold or hot water. These soften as the water trapped in their tissues is released and used in cooking or processing. Thus there is a decrease in volume, especially of leafy vegetables. Celluloses are not digested by man even after cooking but as it has the capacity to bind moisture, it is helpful in smooth movement of the food through the digestive tract. IHM –BANGALORE [2014] Page 5 PRINCIPLES OF FOOD SCIENCE Proteins Egg, fish, poultry and meat are good examples of protein foods. In dals and pulses, the presence of a large amount of starch (50–60 per cent) masks the reactions of proteins during preparation. The effect of preparation on food proteins can be clearly observed in egg, fish, poultry and meat, as these contain mainly proteins, water and variable amounts of fat. All proteins are first denatured and then coagulated by heat. The coagulation occurs between and 90°C. The temperature of coagulation increases with the addition of other ingredients. For example, egg proteins coagulate at 65°–70° C but egg custard coagulates at 85°–90° C. Cooking results in softening of proteins in foods such as eggs, fish, poultry, meat, as water is bound in the process of coagulation. If the coagulated protein is heated further, it loses moisture and becomes dry and rubbery. Therefore it is important to monitor the temperature and time while preparing these food Proteins are precipitated by change of pH, e.g., addition of lemon juice to milk to prepare paneer. Proteins bind water, if the coagulation is gradual, e.g., addition of lactic inocculum results in the formation of solid curd from liquid milk.