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INTRODUCTION TO FOOD SCIENCE AND NUTRITION Definitions: Food is any Substance which is taken into the body to; a) Build up the tissues and keep them in repair. b) Provide energy in the form of heat for warmth and strength for work c) Protect the body from disease. Food Science is the study of the production, processing, preparation, evaluation and utilization of food. Nutrition is the process by which living organism assimilates food and uses it for growth and replacement of tissues. Nutrition: - is the sum total of the process by which living things receive and utilize the necessary materials for survival, growth and maintenance of worn out tissues. Nutrients – is a chemical that an organism needs to live and grow or a substance used in an organism’s metabolism which must be taken from the environment. Malnutrition: - is the condition that results from an imbalance between dietary intake and requirements. It includes under nutrition, which results from less food intake and hard physical work and over nutrition results from excess food intake and less physical activities. Diet: - is defined as food containing all the nutrients in a sufficient amount and in proper ratio. Importance of nutrition;  Keeps us healthy &free of disease, psychological and behavior issues.  Deals with the relationship between our diet and how our body functions. If we want our body to maintain good health then we must supply the essential nutrients.  Nothing heals the body than the body itself, it is for this reason that we need to properly nourish our cells.  When we eat a diet rich in essential nutrients we can then sustain good health and reduce the risks of disease and premature death.  Give one vitality and energy for life 

Help one stay at a weight that's right for them

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Boost immune system

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Improve sports performance

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Delay the effects of aging

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Keep one active and fit into old age

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Help beat tiredness and fatigue

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Protect teeth and keep gums healthy

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Enhance your ability to concentrate and possible alter mood

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Ward off serious illnesses like heart disease, certain cancers, mature-age onset diabetes, and gallbladder disease

Importance of Food Science  

It helps people to develop a healthy lifestyle. It’s a career after school.

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Some foods are medicinal and assist in prevention /curing of some sickness eg. Special diet, salt free diet, sugar free etc

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To assist F&B manager when planning for meals so as to provide correct balanced diet.

COMPONENTS OF A BALANCED DIET A balanced diet means getting the right types and amount of foods and drinks to supply nutrition and energy for maintenance of body cells, tissue, and organs, and for supporting normal growth and development. A diet may be adequate for normal body functioning, yet may not be a balanced diet. An ideal human diet contains fat, carbohydrates, vitamins, minerals, water and fiber all in their correct proportions. These proportions vary for each individual because everyone has different metabolic rates and levels of activity. An unbalanced diet which may be the excess intake of some dietary components and lack of others may result in malnutrition. There are three main categories of nutrients.

Category Macronutrients

Micronutrients Special Nutrient

1.) 2.) 3.) 4.) 5.) 6).

Type of Nutrient Carbohydrates Fats and Lipids Protein Vitamins Minerals Water

Comments required in large amounts

required in small amounts involved in most chemical

reactions within the body; is a major component of blood and serves many other functions A deficiency of any one type of nutrient can lead to disease, starvation or dehydration in the case of water and subsequent death. Fibre is a component of food that is not nutritious but is important to include in our diet. Fibre or roughage is non-digestible carbohydrate and has an important role in aiding the movement of food through the gut. Dietary Reference Value/ Recommended Dietary Allowances (RDA) The Department of Health has compiled charts showing people’s requirements for energy and nutrients. They are meant to help people know how much of each nutrient they need for good nutrition. The figures in the chart are given the general name DRVs or RDAs. DRVs are given for particular group of the population based on age, sex, pregnancy & lactation. These are only recommended not required amounts thus specific conditions may alter the nutritional needs of a given person e.g. Medical problems, illness or undernourished. The categories for which RDAs are divided into are infants, children, males, females, pregnant women, and lactating women (milk producing). They are further divided by age e.g. Infants & children generally need smaller amounts of the nutrients than mature adults but they require more nutrients per unit of body weight because of their rapid growth. Adolescent males require more of some vitamins than teenage females. After growth stops, males need less iron than females. Women generally need more calcium all their lives than men do. Pregnant & lactating mothers need to eat more of virtually all nutrients to remain healthy. Older people, since they are not as active they do not eat food high in energy but must be high on nutritional value. They are therefore encouraged to eat fruits and vegetables & avoid fat, sugar & excess protein. Athletes need to eat well balanced diets, as this enables them to develop greater endurance, lose excess body weight & strengthen muscles. They need to eat food high in carbohydrates as it provides the energy they require to perform well. They also need to drink extra fluid to keep their bodies functioning effectively. Food composition tables

Different tools are used to assess the nutritional situation of groups of people, including families, communities and nations. Food composition tables provide a means to estimate the nutrient content of foods consumed by the population being studied. A food composition table usually consists of a list of selected foods with figures for the content of selected nutrients in each food. FCD are important in many fields including clinical practice, research, nutrition policy, public health and education, and the food manufacturing industry and is used in a variety of ways including: national programmes for the assessment of diet and nutritional status at a population level (e.g. epidemiological researchers assessing diets at a population level); development of therapeutic diets (e.g. to treat obesity, diabetes, nutritional deficiencies, food allergy and intolerance) and institutional diets (e.g. schools, hospitals, prisons, day-care centres) and nutrition labeling of processed foods. NUTRIENTS AND OTHER USEFUL COMPONENTS IN FOOD 1. PROTEINS When food is eaten it’s broken down into components used up by the body. About 17% of human body is made up of proteins and every cell contains protein. Proteins are made up of carbon, hydrogen, oxygen and nitrogen and sometimes sulphur. These elements are arranged in units called amino acids which form the building blocks of proteins. The amino acids are joined together in chains by peptide links. Different proteins are made when different numbers and types of amino acids combine. There are at least 22 different amino acids occurring naturally & each has its own chemical name. They are classified into two groups: 

Essential/ Indispensable amino acids Non-essential/Dispensable amino acids

Essential amino acids have to be supplied in the diet, while non-essential amino acids are made in the body. Essential amino acids (Indispensable)  

Isoleucine Leucin

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Lysine

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Methionine

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Phenylanine

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Threonine

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Tryptophan

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Valine

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Histidine (essential for children)

Non-essential amino acids (dispesable)  

Alanine Arginine

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Aspartic acid

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Cysteine

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Glutamic acid

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Glycine

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Proline

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Serine

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Tyrosine

Children require all the ten but adults need only 8 of the essential amino acids. Protein foods that contain all the essential amino acids are said to be of high biological value (HBV) or complete/ first class proteins. These are mainly of animal origin e.g. milk, eggs, meat, fish, cheese etc. Proteins of low biological value (LBV) or incomplete/second class do not contain all essential amino acids. These are mainly of plant origin e.g. Pulses, cereals etc. The only plant protein which is complete is soya beans. Functions of Proteins 1. Growth of body cells-e.g. growth of foetus or spurt of growth during adolescence. 2. Maintenance & repair of body cells as a result of natural wear and tear or injury. 3. Provision of heat and energy when other sources of energy are lacking, protein is use first to meet energy needs. 4. Form antibodies to fight infections. 5. Prevention of kwashiorkor Sources 

Animal – all meat, poultry, fish, eggs, cheese, ghee, milk.

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Plants – pulses (beans, peas, lentils), cereals (e.g. rice, wheat, oats), the outer part of potatoes & yams, ground nuts, cashew nuts, green vegetables, pigeon peas, soya beans, etc.

Deficiency of protein causes a disease called kwashiorkor, while excess protein is used as energy & can contribute to excess energy. 2. CARBOHYDRATES

Approximately 1-2% of human body is made up of carbohydrate. This is stored in the liver & muscles for use as a source of energy. They are made up of carbon, hydrogen & oxygen. They are divided into three major groups on the basis of their chemical structure: monosaccharide, disaccharides and polysaccharides. a) Monosaccharides (simple sugars) Chemical formula-C6H12O6 1. Glucose – also known as dextrose is found in fruits, plant juices, honey, milk, and milk products. It enters the body directly it’s consumed. 2. Fructose -also ‘fruit sugar’ is found in ripen fruits, vegetables, honey, plant juices and cane sugar. 3. Galactose- a product of the digestion of lactose (milk sugar). b) Disaccharides (two or double sugars) Chemical formula- C12H22O11 They are made up of two monosaccharide, which are split into two by enzymes in the pancreatic and intestinal juices. Three types; 1. Sucrose – formed from one unit /molecule of glucose and one unit of fructose Glucose + fructose = sucrose Found in sugar cane & sugar, fruits and some vegetables. 2. Lactose – formed from one unit of glucose and one of galactose Glucose + galactose = lactose Found in milk of all animals. 3. Maltose – formed from two units of glucose and results from the breakdown of starch. Also known as ‘malt sugar’ and found in cereals such as barley where it is formed during germination.

Glucose + glucose = maltose Disaccharides are crystalline, sweet and easily soluble, and thus easily digested. These sugars are further classified as follows; 1. Intrinsic sugars – those that form part of the cell structure of plants, e.g. in fruits. 2. Extrinsic sugars – not from cell structure of plants. They include non-milk extrinsic sugars e.g. refined sugar, extracted sugars in honey and fruit juice, sugars added to food and milk sugars. c) Polysaccharides (more than two sugars ) -Formed from a varying number of monosaccharide units known as poly which means ‘many.’ Usually soluble in water and tasteless. They are five types; 1. Starch – is stored by plants in their roots, seeds, bulbs, stems and tubers; and in cereal grains, potatoes and pulses. Starch stored in plants changes into glucose as the fruit ripens, which gives a sweet taste. When digested, starch is changed first to dextrin, then to maltose and finally to glucose. Cooking makes starch more easily digestible. 2. Dextrin – formed when food containing starch is cooked, e.g. bread are baked or toasted, some of the starch becomes dextrin which forms part of the crust and thus is more soluble and gets a sweet taste. 3. Glycogen - formed after digestion in human and animals, to ensure that the body has reserve of energy that can be quickly used. Some glucose is converted into glycogen and temporary stored in the liver and muscles. When required it is converted back into glucose. 4. Cellulose – found in the structural portion of all plants. It cannot be digested, thus act as dietary fibre or roughage. 5. Pectin – a complex polysaccharide formed by some plants, e.g. plums, apples in their fruits and roots. It forms gels in water and is responsible for setting of jams. Function 1. Supply energy. 2. Help body use other nutrients. 3. Regulate other body processes. 4. ‘Protein sparing’ functions if the diet lacks carbohydrate, more protein than usual will be used as an energy source. Sources

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Sugars e.g. table sugar, cane sugars, sweets, honey, fruit, fruit juices, syrup and sweet desserts. Starches e.g. bread, natural flours, corn, potatoes, cereals, rice, cassava, yams, arrowroots, green bananas, maize, wheat etc. Cellulose plentiful in certain vegetables such as lettuce, celery, fruit, with skin, green legumes, leafy vegetable, whole grain cereal, millet.

Deficiency- incase a diet is low in carbs, protein is then used to provide energy at the expenses of being available for growth and repair of tissues. Excess is stored as fat and contributes to development of obesity.

3. FATS Fats and oils have the same basic chemical structure, but their physical appearances differ at room temperature. -Fats are solid at room temperature. - Oils are liquid at room temperature. Like carbohydrates fats are composed of carbon, oxygen and hydrogen elements in different proportions. These elements make up molecules of glycerol and fatty acids, which combine to form fat molecules. The scientific name for the fat molecule is a triglycerol/ triglyceride. Fatty acids may be either saturated or unsaturated. Examples of fatty acids are: - Butyric acid- milk, butter -Lauric acid- dairy foods, coconut oil - Stearic acid- beef fat - Oleic acid- in most fats and oils especially olive oil. Functions 1. Provides a convenient and concentrated source of energy, supplying more energy than carbohydrates and protein. 2. Surrounds and protects certain vital organs e.g. kidney, glands, heart from physical injury. 3. Forms an insulating layer (adipose tissue) beneath the skin to help preserve body heat and protect the skeleton and organs.

4. Forms part of the structure of cell membrane throughout the body, especially in the brain. 5. Provides a source of the fat- soluble vitamins A, D, E, K. 6. Provides a reserve of energy for long- term storage, which can be used if energy intake is limited. 7. Provides texture and flavor in food and helps to make it palatable. 8. Foods containing fat provide a feeling of fullness (satiety) after a meal, as fat digestion is slow. Sources 4. Animal - Meat-lard, bacon, suet. -Dairy products- milk and milk products (butter, cheese, cream) -Egg York -Fish- liver oils (cod, halibut) -

Oily fish (tuna, herring, salmon, pilchard, etc)

5. Plant sources -Seeds – cotton, maize, sesame, olive, soya, sunflower, nuts and pulses -Peanut. -Fruits –avocado 

Deficiency and excess of fat- a diet that is totally fat free would result in fat soluble vitamin deficiencies. Excess intakes lead to obesity or cardiovascular disease. 4. VITAMINS Vitamins are a group of chemical substances which the body requires in small amounts, but as it cannot make most of them by itself, they must be supplied by the diet . They are required to regulate the maintenance and growth of the body, and to control metabolic reactions in cells. A diet lacking in one or more vitamins will result in specific deficiency diseases, many of which occur in the poor countries. Vitamins can be classified according to the substance in which they dissolve. There are two groups;

1. Fat- soluble vitamins; vitamins A, D, E and K. 2. Water soluble vitamins; vitamin C and the vitamin B complex. A. FAT SOLUBLE VITAMINS i)

Retinol (vitamin A)

Functions i. ii.

Required to make a substance called visual purple, which is formed in the retina of the eye to enable it to see in dim light. Required to keep the mucous membrane in the throats and the digestive, bronchial and excretory systems moist and free from infections.

iii.

Required for the maintenance of healthy skin.

iv.

Required for normal growth of children, particularly the bones and teeth.

Sources -Found as retinol in animal food, especially milk, cheese, eggs(yolk), butter, oily fish etc. -Found as beta (β) – carotene in plant foods, especially carrots, spinach, water cress apricots, parsley, cabbage, tomatoes, prunes. It gives plants their orange/ yellow colour, though in green vegetables it’s masked by chlorophyll. -It’s converted into retinol in the body. Requirements  

Since vitamin A is fat soluble, it can be stored in the body, mainly in the liver, so as daily supply is not always necessary. Too much of it can be poisonous as it affects skin and joints especially in children, thus intake of Beta- carotene is advised for expectant mothers  Deficiency – night blindness. Prolonged deficiency leads to degeneration of cornea (exophthalmia) and total blindness. ii)

Cholecalciferol ( vitamin D)

-Stored in the fatty tissues of the body and liver. Functions  

Helps body absorb calcium Helps in building of strong bones and teeth.

Sources  

Found in good supply in;-liver, fish liver oils, oily fish. Found in smaller amounts in; - egg yolk, margarine (added by law), milk and dairy products.

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Sunlight is also another important source.

Requirements 

Too much vitamin D can be dangerous as it results in excess absorption of calcium into the blood. The extra is then deposited in the lungs and kidney which causes death.  Deficiency-causes rickets in children and osteomalacia in adults. iii)

Tocopherol (vitamin E)

Functions  

The main function of vitamin E in the body is that of an antioxidant. An increased level of it the tissue may protect against cardiovascular disease and cancer.

Sources Found in small quantities in many plants e.g. lettuce, grasses, peanuts, seeds, wheat germ oil, vegetable oils (sunflower seed oil). Also found in milk and milk products, and egg yolk.  Deficiency is rare, but premature babies and people who have a problem absorbing fat may show signs of an increased breakdown of red blood cells, muscle tissue damage and swelling of adipose (fatty) tissue. iv)

VITAMIN K-(Naphthoquinone)

Several substances with similar functions are known to exist in this group , so there is more than one vitamin K. Functions 

Assists in the production of the coagulation factor in the blood, to enable it clot properly after an injury.

Sources  

Widely distributed in foods especially in leafy vegetables such as spinach. Bacteria found in intestinal track produce useful supply of the vitamin.

Deficiency is rare, but as a precaution, babies are given immediately after birth so that their blood will clot if they are injured.

WATER- SOLUBLE VITAMINS These type of vitamins need to dissolve in water before the body can absorb them, for this reason they cannot be stored in the body. There is a need for a fresh supply of these vitamins every day. They include vitamin C and B-complex. 1. VITAMIN B-COMPLEX There ...