Unit 1: DEFINITION AND SCOPE OF FOOD SCIENCE

Introduction

• Food is defined as anything solid or liquid which when swallowed, digested and assimilated and nourishes the body.

• Food science is a systematic study of the nature of food materials and the scientific principles underlying their modification, preservation and spoilage.

• It is a discipline in which the biological and physical sciences and engineering are used to study the nature of foods, the causes of their deterioration, and the principles underlying food processing. It deals with acquisition of new knowledge to elucidate the course of reactions or changes occurring in foods whether natural or induced by handling procedures.

• Food is a mixture of many different chemical components. The study of food science involves an understanding of the changes that occur in these components during food preparation whether natural or induced by handling procedures many physical and chemical reaction occur during food preparation these reactions may be a result of the interaction between components with the medium of cooking, and the environmental conditions like heat cold light and air to which they are subjected during cooking.

• Study of food science also includes understanding the nutritive value of different foods and methods of preserving them during cooking this information provides a foundation of theory and method on which they build the study of food preparation.

Inter-relationship with food chemistry

• It is the science that deals with the composition, structure and properties of food and with chemical changes that take place in food.

• It forms a major part of food science and is closely related to food microbiology.

• The chemical composition of food tells which micro-organism can grow on it and the changes that take place in the food because of their growth.

• Changes can be desirable and undesirable which can lead to contamination of the food and further leading to food poisoning, food infection or just spoiling of the food rendering it unfit for consumption.

Inter-relationship with food microbiology

• Microbiology is the study of micro organisms. Micro organisms are very small, usually single celled organisms which are not individually visible to the naked eye. If they are present in large number in food can lead to food poisoning. They are being used by man for production of certain foods e.g. bread and yoghurt.

• Interactions between Micro-organisms, plants and animals are natural and constant. Since the human food supply consists basically of animals or products derived from them, it is understandable that our food supply can contain micro-organisms in interaction with the food.

• A knowledge of the factors that favors or inhibit the growth of Micro -organisms is essential to an understanding of the principle of food spoilage and preservation.

• Food chemistry and food microbiology are intimately related to food processing because the processes to which food needs to be subjected to improve its texture, flavor and aroma depend on its composition and ingredients. The time and temperature for food processing depends not only on the chemical composition of food but on its microbial load and the type of packaging to be used.

Inter-relationship with food processing

• The growing public demand for meals away from home has made the problem of serving safe, wholesome food more critical and challenging. This makes it imperative for food handlers to understand and implement the basic principles of the food science to enable them to prepare and serve high quality products over extended hours.

• Rapid urbanization has lead to increase in demand of convenience foods (foods that require little labor and time to prepare e.g.. frozen peas). To these food additives are added to restore properties and to bring certain changes for storage. The special requirements for them are:

• They need to be handled properly.

• Not to be stored in open.

• Maintenance of hygienic condition.

• Similarly numerous food choices exist like canned foods, snacks, soups etc.

Constituents of food

Food constituents are substances that provide nourishment essential for the maintenance of life and for growth. Food constituents are classified into the major groups which includes: carbohydrates, proteins, fats, vitamins, minerals, fiber & water.

1. Carbohydrates:

They are the chief source of energy in our diet. They are chemical compounds containing carbon, hydrogen and oxygen. They provide instant energy to our body. The chief sources of carbohydrates are: rice, wheat, maize, barley, potato, sugarcane, beetroot, banana, etc. The two kinds of carbohydrates are

1. Starch

2. Sugar

• Starches are found in grains, legumes and tubers while sugar is found in fruits and plants. Carbohydrates are used by the cells in the form of glucose. 
• After absorption from small intestine, glucose is processed in the liver, which stores some as glycogen, a starch like substance and passes the rest into bloodstream. 
• Glucose forms triglycerides, which are fat compounds which can be broken down into ketones. 
• Glucose is carried by the bloodstream to the muscle and organ to be oxidized and excess quantities are stored as fats to be retrieved at times of low carbohydrate intake. 
• The carbohydrates containing the most nutrients are the complex carbohydrates such as unrefined grains, tubers, vegetables and fruits which also provide proteins, vitamins, minerals and fats. 
• A less beneficial source is food made from refined sugar such as candy and soft drinks which are high in calories but low in nutrients.

Classification of Carbohydrates

MONOSACCHARIDES:
They are the simplest form of CHO found in nature.  They differ from one another because of their arrangement of different atoms around the carbon chain and because of this they have different properties and vary in their degree of sweetness.

Glucose- it is the most important CHO used by the body.
It is absorbed into the blood stream after CHO is digested in the body. It is also known as dextrose. Available in powder and liquid form. It is found in varying amounts in fruits and vegetables. Found in large amount in fruits like grapes, smaller amount in vegetables like peas.

Fructose-It is sweetest of all sugars, is also known as fruit sugar and levulose because it is found in fruits and honey.
In human body it is converted to glucose and oxidized as a source of energy.

Galactose-It is not present in food as such, but produced when lactose a disaccharide is broken down during digestion.

DISSACHARIDES 

They are double sugars composed of two monosaccharides linked together with the removal of a water molecule. 

Sucrose-It is table sugar
It is produced in plants by the condensation of glucose and fructose.
It is found in many fruits and vegetables like sugarcane and sugarbeet contain relatively large quantities.
It is from cane and beet that sugar is extracted commercially.

Maltose-It is made up of two units of glucose.
During the germination of whole grains starch is broken down into maltose
In the body maltose is formed during digestion of starch.

Lactose-It is milk sugar
Made up of one unit of glucose and one unit of galactose.
It is least sweet of all sugars and easily fermented to lactic acid by lactic acid bacteria while preparing curd and cheese.


 OLIGOSACCHARIDE
Any carbohydrate of from three to six units of simple sugars (monosaccharides). A large number of oligosaccharides have been prepared by partially breaking down more complex carbohydrates (polysaccharides). Most of the few naturally occurring oligosaccharides are found in plants.
Raffinose and stachyose may promote the growth of beneficial intestinal bacteria, but are currently not considered prebiotics.

Raffinose - also called melitose, is composed of 3 sugars: galactose, glucose and fructose. Examples of foods naturally high in raffinose are beans, asparagus, cotton seeds, sugar beet molasses, cabbage, broccoli, Brussel’s sprouts, sweet potatoes and whole grains . Raffinose as a sweetener is extracted from sugar beet molasses.

Stachyose - Stachyose is composed of 4 sugar molecules: 2 galactoses, glucose and fructose. It is found mainly in beans and peas .


POLYSACCHARIDES 

They are complex carbohydrates made up of 100-2000 glucose units linked to each other in chain or branched form. The number of glucose units, their arrangement and linkage to one another influence the properties of the polysaccharides.

Dextrins- They are smallest and simplest of all polysaccharides.
They are formed by dry heating or acid hydrolysis of starch.
They are slightly soluble have a mild sweet taste and limited thickening ability.

Starch-It is found in most parts of the plant as a reserve store of carbohydrate.
It is usually present in the seed and root in large amounts.
Starch consists of long chains of glucose units present in two forms amylose and amylopectin.

STARCH

Amylose –
 It is a large molecule made up of 200 or more glucose units .
They are present as linear chain which can bond to each other by hydrogen bonds and form a gel.
Starches from different sources differ in their amylase content. Amylose does not have sweet taste, is slightly soluble, has good thickening ability and is present 20-30% of total starch in most grains.

Amylopectin –
It is also made up of glucose units only and are present in form of large branched polysaccharide.
The molecules of amylopectin are very large and as it is branched structure it is sparingly soluble, not sweet and is predominant form in the starch granule with low gelling
Cereal starches, such as corn, rice, wheat, oats, sago and tapioca are used as thickening and gelling agents.

STARCH

EFFECT OF COOKING ON STARCH

GELATINIZATION (wet heat)

• When starch granules are mixed with cold water they do not dissolve but form a suspension.
• When the water is heated, the granules begin to swell. The heat energy breaks the hydrogen bonds in the starch granules and facilitates the entry of water into the granules. At the same time some amylose from the granules leaches into the cooking water.
• The starch chains in the granules absorb moisture and begin to uncoil from their tightly packed configuration.
• The size of the granules increase as more and more water enters. The water in the granules gets bonded to amylose and amylopectin.
• The mixture becomes viscous and translucent after continuous heating. Swollen granules find it difficult to move past each other, adding to the viscosity of the mixture.
• This process of swelling of the starch granules and formation of viscous starch paste is called
• GELATINIZATION
• The temp at which the granules swell is called the GELATINIZATION TEMPERATURE and is characteristic of each starch.

GELATION

• Gelatinized starch mixture may exhibit flow properties & remain a sol or may cool and set to from a gel.
• The amylose , which has leached  out  of the swollen starch granule , forms Hydrogen  bonds with other amylose molecules as the starch paste cools & loses energy
• Amylose molecules moves slowly forming bonds & a 3 dimensional continuous network of amylose is formed in which swollen granules are trapped
• This forms a continuous phase of the newly formed starch gel in which water is dispersed. The starch mixture is transformed formed into a gel & no longer exhibits flow properties.

RETROGRADATION

• Amylose starches form gel readily but these gels are less stable as amylose chains have a tendency to recoil and partially recrystallize. Some hydrogen bonds which hold the gel together break and amylose molecules move around forming new bonds.
• As the gel stales amylose molecules rearrange themselves in an orderly manner in crystalline regions. This is accompanied by loss of solubility and release of water from the gels, causing food defect.
• Thus retrogradation occurs when a starch gel stales or when it is frozen. A starch gel which has retrograded loses its smooth texture and feels gritty when eaten.
• The rate and extent of retrogradation are influenced by temp, size, shape and concentration of starch. Starch retrogrades rapidly at 0º C.
• The texture defects caused by retrogradation in foods which can be heated are temporarily corrected by warming the food containing starch.
• The problem of retrogradation is of concern in cold starch based gels. This can be corrected by using starches which are stable to freezing and thawing.

DEXTRINIZATION (dry roasting of starch)

• When starch is heated without any water, the temp rises rapidly beyond 100C.
• Water which is naturally present in flour and high temp brings about chemical changes or degradation of flour, splitting the starch molecule at one or more of the α1,4 glucoside linkages.
• This reaction is called dextrinization and the short chain starch molecules of varying length formed are called dextrins.
• This process is seen when flour is browned while making brown roux for gravies and sauces. Browned flour has lesser thickening ability because of formation of short chain dextrins.

Uses of Carbohydrates in Food Preparation

• Starch from various sources in its natural form is used as a thickening and gelling agent in a wide range of products. It is the primary thickening agent used in soups and sauces.
• These sauces are used in vegetable and meat based preparations, salads and pastas. It is also used in custard sauce, puddings, pie fillings and soufflés.
• Sugar has a wide range of uses apart from sweetening and energy giving. Sugar cookery involves controlled formation of crystals which has a direct bearing on the texture of crystalline candies such as fondants and fudges.

Some uses of Carbohydrates:

Carbohydrates	Use
Refined flour	Thickening sauces and soups specially used in the form of a roux.
Rice	Thickening soups and rice puddings
Arrowroot	For clear soups
Tapioca	Used for pudding
Potato	Used for soups which could curdle at high temperatures
Waxy rice flour	White sauces and starch thickened pudding which need to be stored frozen and thawed before cooking.
Corn flour	Thickening soups, sauces, gravies and anti-caking agent.
Pectin	Setting agent in jams, jellies and marmalades
Seaweed extracts	Prevent ice crystal formation in ice cream
Glucose	Used as a humectant in confectionery
Caramel	Used as coloring and flavoring agent in Christmas cake, soup mixes, instant pudding etc.
Invert Sugar	Prevents formation of sugar crystals in preserves and fondants

2. Proteins:

Proteins are made up of amino acids. Proteins are formed by different combinations of twenty amino acids. Each amino acid contains carbon, nitrogen, hydrogen and oxygen. Some proteins contain elements like sulphur, phosphorus and iron as well.

Proteins can be classified into two groups depending on their source: Animal proteins are obtained from animal products like milk, cheese, egg, fish or meat.
Vegetable proteins are obtained from plants like pulses, soyabeans, nuts like cashew nuts, groundnuts, grains like barley, etc.

Animal proteins are considered to be better than vegetable proteins as they are more easily digested and absorbed by the body. Daily requirement of proteins for adults is about 1 gram per kg body weight. Children may require 2 to 3.5 grams per kg body weight because of their continuous growth.

Proteins also help to repair damaged body tissues. 

Proteins can also be utilized to provide energy during starvation. One gram of protein when burnt yields about 4 calories. 

The primary functions of proteins include building and repairing of body tissues, regulation of body processes and formation of enzymes and hormones such as insulin that regulate communication among organ and cells, and other complex substances that govern body processes. 

Animal and plant proteins are not used in the form they are ingested but are broken down by digestive enzymes called proteases into nitrogen containing amino acids. 

Proteases disrupt the peptide bonds by which the ingested amino acids are linked, so that they can be absorbed through the intestine into the blood and recombine into the particular tissue needed. 

Proteins aid in the formation of antibodies that enable the body to fight infection. 

Proteins serve as a major energy supplier. There are distinctive kinds of proteins, each performing a unique function in the body. 

Proteins form a major part of human body, next to water. 

Enzymes are chemical substances that take part in several chemical reactions. 

Enzymes are chemically proteins. For example, salivary amylase is an enzyme produced by our salivary glands that breaks down starch into sugar.



The composition of proteins in the body is: muscle contains about 1/3 protein, bone about 1/5 part and skin consists of 1/10 portion. The rest part of proteins is in the other body tissues and fluids. Even blood contains loads of proteins. 

In fact the hemoglobin molecule is composed of  proteins. Our body requires proteins for the purpose of maintenance and healthy growth. 

The need for consuming proteins is especially more for infants, young children, pregnant women and recovering patients. There is a constant breakdown of proteins in the body and this explains the reason why we need to consume proteins on a regular daily basis. It becomes of prime importance to ensure the daily-recommended protein intake, so as to improve health. Sources of protein include meat, fish and eggs, as well as non-animal products, such as beans and nuts.



3. Fats:



Fats like carbohydrates are energy-giving foods but are greatly concentrated sources of energy. One gram of fat when burnt gives 9 calories of energy. Fats are made up of carbon, hydrogen and oxygen. However, compared to carbohydrates, fats contain lesser amount of oxygen, and hence produce larger amount of energy when oxidized.



Fats can be classifies as animal fats and vegetable fats depending on their source. Butter, ghee, milk, fish, meat, etc., are sources of animal fat while nuts and vegetable oils like groundnut oil, sunflower oil, mustard oil and sesame oil are sources of vegetable fat.



They produce more than twice energy compared to carbohydrates. Fat is stored in the body for later use when carbohydrates are in short supply. Animals need stored fat to tide them over dry or cold seasons as do human during time of scarce food supply.



A major part of the food we eat is used to derive energy for day-to-day activities. A small part of the remaining food is converted into fat and stored in the body. Fats thus constitute an energy bank in the body which provides energy whenever the need arises. Fat is mainly stored under the skin and protects internal body organs from jerks and shocks. Fats help in the absorption of vitamins A, D, E and K as these vitamins are soluble in fats. Fats also make food tastier. Fats take a longer time for digestion, hence we do not feel hungry for a long time after eating fried food.



Fats are broken down into fatty acids that pass into the blood to form the triglycerides. The fatty acids that contain may hydrogen atoms are called saturated fatty acids and are derived mostly from animal sources. Unsaturated fatty acids are those having some of the hydrogen atoms missing. This group includes monounsaturated fatty acids, which have a single pair of hydrogen missing and polyunsaturated fatty acid, which have more than one pair missing. Polyunsaturated fats are found mostly in seed oils. Saturated fats in bloodstream have found to raise the level of cholesterol and polyunsaturated fat tends to lower it. Saturated fats at room temperature are solid while polyunsaturated fats are liquid.



4. Vitamins:



Vitamins are organic compounds which enhance the metabolism of proteins, carbohydrates and fats. Without vitamins the breakdown of food could not occur. Certain vitamins participate in the formation of blood cells, hormones, nervous system chemicals and genetic materials. They are classified into two groups i.e. fat-soluble and water soluble vitamins.Fat-soluble Vitamins: Includes vitamin A, D, E and K.




They are usually absorbed with food that contains fat, further broken down by bile and the emulsified molecules pass through the lymphatic and veins to be distributed through the arteries. Excess amount is stored in the fats, liver and kidneys. As they can be stored so they don’t have to be consumed everyday.



Vitamin A: It is essential for the health of epithelial cells and for normal growth. Deficiency leads to skin changes and to night blindness or failure of dark adaptation due to the effects of deficiency on retina. It can be obtained in the diet foods of animal origin such as milk, eggs and liver. In developing countries it is obtained from carotene, which is present in the green and yellow fruits and vegetables.



Vitamin D: Acts as a hormone and regulates calcium and phosphorous absorption and metabolism. Some vitamin D is obtained from eggs, fish, liver, butter, margarine and milk while human gets most of it from the direct sunlight. Its deficiency causes rickets in children or osteomalacia in adults.



Vitamin E: Is essential for many vertebrate animals but its role in the human body has not been established. No clear evidence exist that it alleviates any specific disease. It is found in seed oils and wheat germ.



Vitamin K: It is necessary for the coagulation of blood. It assists in forming enzymes prothrombin which in turn is needed to produce fibrin for blood clots. Vitamin K is produced sufficiently in the intestine by bacteria and also provided by leafy green vegetables such as Spanich and egg yolk.Water-soluble Vitamins: Includes vitamin C and B complex.



Vitamin C: They cannot be stored and have to be consumed on daily basis to replenish body needs. Vitamin C is important in synthesis and maintenance of connective tissues, it prevents scurvy. Main source is citrus fruits.



Vitamin B complex: The important B-complex vitamins are thiamine (B1), riboflavin (B2), nicotinic acid or niacin, pyridoxine (B6), pantothenic acid, lecithin, choline, inositol, para-aminobenzoic acid (PABA), folic acid and cyanocobalamin (B12). These vitamins are used in a range of metabolic reactions in the body and prevent diseases such as beriberi and pellagra. They are found in yeast and liver.



5. Minerals:



Inorganic mineral constituents are required in the structural composition of hard and soft body tissues, they also participate in such processes as the action of enzyme system, the contraction of muscles, nerve reactions, and the clotting of blood. These mineral nutrients, all of which must be supplied in the diet are of classes, The major elements such as calcium, phosphorous, magnesium, iron, iodine, and potassium; and traces elements such as copper, cobalt, manganese, flourine and zinc.



Calcium is needed for muscle, heart and digestive system health, builds bone, supports synthesis and function of blood cells. Dietary sources of calcium include dairy products, canned fish with bones (salmon, sardines), green leafy vegetables, nuts and seeds.



Phosphorus is a component of bones and energy processing and many other functions. In biological contexts. It combines with calcium in bones and teeth. Plays an important role in energy metabolism of the cell.



Magnesium is required for processing human metabolism and for maintaining the electrical potential in nerve and muscle cells. Deficiency can result in malnourished people, especially alcoholics, leads to tremors and convulsions.



Sodium is a systemic electrolyte and present in extra cellular fluid, which it plays a role in regulating. Too much use can cause edema. Now its evident that excess use of table salt Sodium-Chloride contributes to high blood pressure.



Iron is required for many proteins and enzymes, notably for the formation of hemoglobin. Sources include red meat, leafy green vegetables, fish (tuna, salmon), eggs, dried fruits, beans, whole grains, and enriched grains.



Iodine is needed to synthesize hormone of the thyroid gland. Deficiency cause goiter. Traces elements are other inorganic substances that appear in the body in minute amounts and are essential for good health. They include copper, which is required component of many redox enzymes. Its deficiency is associated with the failure to use iron in formation of hemoglobin. Zinc form enzymes, its deficiency causes impair growth in teeth and bones. Fluorides is important for protecting against demineralization of bone. Other trace elements include chromium, molybdenum, and selenium.



6. Fiber:



The cell walls of all plant cells are made up of cellulose. Cellulose cannot be digested by our digestive system. Although cellulose does not have any nutritive value for us, it is needed in our diet for proper functioning of the digestive system. Cellulose forms the fibre content of our diet and is referred to as roughage. Roughage provides the alimentary canal muscles with bulk against which they contract easily. This allows for more efficient movement of food in the alimentary canal, especially in the large intestine. Roughage helps in the regular movement of bowels. People who do not include roughage in their diet suffer from constipation. Salad, fruits, vegetables, whole cereals and whole legumes and pulses constitute the main sources of roughage in our diet.



7. Water:



Water forms about 70% of our body weight and is an important constituent of all body cells. Water is required for all the biological processes in our body. By weight water constitutes two third of the weight of a human body. It doesn’t only maintain the temperature of body but removes waste products. In this way water is essential constituent of balanced diet. Although water does not provide energy, it is a very important nutrient. It performs the following functions in the body:Water transports food, wastes, gases and other chemicals (like hormones) throughout the body.
Water helps in digestion by dissolving the nutrients which can then be absorbed or digested by the body.
Water carries waste out of the body as sweat and urine.
Water helps to regulate the body temperature.



The amount of water needed by a person depends on one’s age, type or work and climate. Athletes and persons doing more of physical work must consume plenty of water as they lose a large amount of water as sweat. For the same reason more water is required by our body in summer than in winter.