Chapter : 1 Nature of Food Study

1. Chapter: 1Nature of FoodStudy Dr. MayHamdan Department of nutrition and foodtechnology

2. Nature of FoodStudy • The basic function of food is to keep us alive and healthy. • In recent years, the study of food has been accepted as a distinct discipline (field) and is known as Food Science. • So the study of food science involves understanding the nature, composition and behavior of food materials under varying conditions of storage, processing and use.

3. Food science embraces (includes) many disciplines: For example: • 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.

4. 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 sociocultural 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.

5. Aim of Study of Food Science • The foods we eat are derived from plants and animals. • Food components vary, depending on many factors: • the growth, • maturation, • harvesting • slaughtering, • storage • and handling of plant and animal parts used as food.

6. There are furtherchangesin the food components during food preparation and processing as a result of many changes or factors, and they are: • their interaction with one another, • their interaction with the cooking medium • and their interaction with the environment. • The temperature at which the food is cooked and the duration of cooking also bring about changes in the components of the food.

7. So the aim of the study of food science is: to understand these changes (changesin the food components during food preparation and processing) and control them in order to obtain food preparation or products, which have desirable characteristics.

8. Food Science and Food Technology • The dividing line between food science and food technology is often unclear because food technology uses and exploitsاِسْتَثْمَرَthe knowledge of food science. • The link between food science and technology is well illustrated in solving the foremost (principle) problem of feeding the world’s rapidly increasing population.

9. The problems inherent (مُتَأَصِّل) in deciding what foods meet the nutritional needs of people, the nutritional content of various foods, how to preserve and serve food with minimum nutritional loss, these form part of food science. • But to use this information, it must be applied—foods must be grown, stored, processed, preserved and transported on a large scale and this is the area of food technology.

10. Food science includes many sciences but a chemical approach to the subject is a natural and important one. Because: • Firstly, food materials are composed entirely of chemical compounds. • Secondly, nearly all manufactured foods have “additives”, which are chemical compounds. These may be added to improve color, flavor, texture or other desirable qualities. • Further, the changes that occur in food when it is processed, cooked, eaten and used by the body are chemical changes.

11. Physico-chemical aspects of food help us to understand the nature and properties of food. For example, • emulsions and emulsification are an important example of colloidal food systems. Milk and butter are good examples of natural emulsions. Note: emulsifiers is to facilitate the mixing together of ingredients that normally would not mix, namely fat and water. • Physical conditions such as pressure and temperature have often important effects upon food systems and the rate of change, which occurs.

12. Definitions • Food is that which nourishes the body. Only those substances which when eaten or drunk and absorbed by the body produce energy, promote growth, repair tissues and regulate these processes are foods. • Nutrients The chemical components of food, which perform these functions (produce energy, promote growth, repair tissues and regulate these processes). Some foods such as milk and cereals supply many nutrients while others such as sugar provideonlyonenutrient (sucrose = glucose and fructose)

13. science of nutrition The study of various nutrients, their functions, food sources and their utilization by the human body and their effect on human wellbeing. Foods provide six types of nutrients: • proteins, • carbohydrates, • fats, • vitamins, • minerals • And water. In addition, the body also requires a continuous supply of oxygen. There are over 40 essential nutrients, which are supplied by the food we eat.

14. Malnutritionmeans an undesirable kind of nutrition leading to ill health. The lack, excess or imbalance of nutrients in the diet may result in malnutrition. It includes both undernutrition and overnutrition. • Undernutrition is a state of insufficient supply of essential nutrients to the body. • Overnutrition is the result of excessive intake of nutrients, which disturbs normal body functions.

15. Deficiency of nutrients can occur in two main cases: • if the supply of the nutrient is inadequate to meet the body’s need • or the nutrient supplied is not absorbed and is thus not available to the body.

16. The word health refers to the condition of the body. • Good health indicates not only freedom from disease, but physical, mental and emotional fitness as well.

17. Nutrients provided by food perform three basic functions in our bodies. • Nutrients supply energy, • provide materials for growth and repair of tissues, • control and regulate the body processes.

18. Specific Nutrients in Foods and Their Functions • The foods we use daily include, rice, wheat, dal, vegetables, fruits, milk, eggs, fish, meat, sugar, butter, oils etc. Note: Dal is a preparation of pulses (dried lentils, peas or beans) which have been naked of their outer covering and split (divided). • These different foods are made up of a number of chemical components called nutrients.

19. Nutrients are classified according to their chemical composition to the following classes: • Carbohydrates, supply energy. Each gramme of carbohydrate supplies 4 kilocalories of energy to the body. Carbohydratescontaintheelementscarbon, hydrogen and oxygen.

20. Starchispresentmainly in cereals, pulses, roots and tubers. • Sugar is found in fruits, sugar cane and sugar beet Note: Sugar beet, a cultivated plant, is a plant whose tuber contains a high concentration of sucrose. It is grown commercially for sugar production

21. Oils and Fats are extracted from plants and animal sources and are used in food preparation and service. These are composed of glycerol and fatty acids. Fats and oils contain carbon, hydrogen and oxygen. But the amount of oxygen present in these is much smaller than in carbohydrates. Each gramme of oil or fat supplies 9 kilocalories of energy.

22. Proteins are the third major nutrient present in foods. • They are present in plant and animal foods, • All the proteins contain the elements carbon, hydrogen, oxygen and nitrogen. Thus, the presence of nitrogen distinguishes proteins from carbohydrates and fats. • Proteins are made up of smaller compounds known as amino acids.

23. Mineral elements form an important group of nutrients. • Minerals include those elements, which normally form salts and are converted to ash on exposure to high temperature (about 550°C). Mineral elementsinclude • calcium, • phosphorus, • magnesium, • sodium, • chlorine, • potassium, • sulphur.

24. Vitamins: are organic compounds present in small amounts in foods, which must be provided to the body, to ensure normal growth and maintenance of the body. • Vitamins include two types: • fat soluble ones such as A, D, E and K • and water-soluble, vitamin C (ascorbic acid) and B-complex group.

25. The B-complex group consist of the following: • Vitamin B1 (thiamine) • Vitamin B2 (riboflavin) • Vitamin B3 (niacin) • Vitamin B5 (pantothenic acid) • Vitamin B6 (pyridoxine) • Vitamin B7 (biotin) • Vitamin B9 (folic acid) • Vitamin B12 (cobalamins)

26. Water is an essential part of the body structure. It is a carrier of nutrients and regulator of a number of body functions. Our needs of water can be met by tow sources: • A major part of our need for water is met by the water we drink. • A part of our need for water is met by the water in beverages such as: • tea, • coffee, • fruit drinks and juices • and the water present in food preparations included in the meals.

27. All individuals need the same nutrients for the same body function. The only variation is in the amounts of each nutrient required according to the following factors: • age, • size, • activity etc. Forexample, thoughallpersons need energy for work, a man who carries loads may need more energy than a man who works at a desk job.

29. FoodMicrobiology • Microorganisms: are minute living organisms, which vary in size from algae, which are just large enough to be seen by the naked eye (about 100 micron) to viruses, which are so small (about 0.1 micron) that these can be seen with an electron microscope only. • The micro-organisms that are usually found in food are: • moulds, • yeasts • and bacteria.

30. These occur mainly in: • soil, • air, • water and sewage. • These enter animal and plant foods at various stages of production and storage. These multiply in food, if conditions are favorable.

31. As a result of their growth – microorganisms- they may bring about changes in the food. • Some of the changes are desirable. a variety of food products are added to our menu as a result of microbial activity. For example, • curds are formed from milk by the action of lactic bacteria, • bread is fermented with the help of yeast.

32. But it is also true that moist foods kept in a warm place spoil due to action of microorganisms. • The presence of some microorganisms or the toxin they produce in food is known to be harmful to the consumer. • Therefore, it is important to know the kind of microorganisms present and their modeof action in foods for effective use of food.

33. FoodPoisoning • Food poisoning occurs when foods containing poisons of chemical or biological origin are eaten. • The symptoms are: • abdominal pain and • diarrhea, • usually accompanied by vomiting, which follow 2-36 hours after eating such food.

34. the most common cause of food poisoning is: • the presence in food of harmfulbacteria • or the presence of toxins produced by them. • Most food poisoning incidents occur due to unhygienic practices and therefore these are preventable.

35. Pathogens (disease producing bacteria) find their way into food through: • use of infected animal foods, • infected food handlers, • unclean equipment, • household pest and water. • The storage of prepared food at room temperature may accelerate multiplication of pathogens present.

36. Food poisoning can be prevented by: • strict adherence to cleanliness in purchase, storage, preparation, handling and service of foods • use of appropriate temperature during processing and storage of leftovers.

37. FoodPreservation • If food is to be kept in good condition for any length of time, it is essential that the growth of microorganisms be prevented. • This can be done by either: • killing the microorganisms and then storing the food in conditions, where further infection is impossible • or by creating an environment which is not suitable for their multiplication.

38. Methods of FoodPreservation • Dehydration Principle: Removal of water which prevents growth and multiplication of microorganisms. Examples Dried foods such as cereals, pulses, nuts, oilseeds, vermicelliشعيرية, and milkpowder.

39. 2. Chemical Preservatives Principle: kill or inhibit the growth of microorganisms Examples: • Salt, sugar, vinegar (pickles and sauces صلصة), potassium meta bisulphite (squash).

40. Sterilizationbyheat Principle: Usingtheheattokillthemicroorganisms. Food is stored in a sealed container and cannotbe re-infected. Examples: Cannedmilk, meat, fish, vegetables and fruits.

41. Freezingor use of lowtemperatures Principle At verylowtemperaturemicrobialgrowthiseitherretardedorprevented Examples Frozenfoods, vegetables, fruits, meat, chicken, shrimpروبيان

42. 5. Irradiation Principle Highpotencyradiationskillthemicroorganisms and pests Examples Irradiatedpotatoes, wheat etc.