Composition of food and proximate analysisPresentation Transcript
Composition of food The term “food” refers to the broad range of ediblematerials that comprise the essential body nutrientsrequired for life and growth, such asproteins,carbohydrates,fats, vitamins, or minerals. Food contains chemical molecules.Chemical compositionmay be determined in laboratory
Cont… Chemical substances found in the largest amountsin food: Carbohydrates Fats Protein Water found inside cells in plants and animals Vitamins Minerals
Carbohydrates Carbohydrates are organic compounds of carbon , hydrogenand oxygen. There are two major types of carbohydrates infood : Sugar and Starch. The bodys principal source of energy. All sugars and starchesthat we consume are carbohydrates. Examples include table sugar, wholegrains, pasta, fruit, popcorn, vegetables and more . One gramof carbohydrates yields about 4 Kilocalories of energy. Excessof carbohydrates in the body is converted into fat which isstored in the body.
Chemical classification of sugar Carbohydrate are classified on the basis of number ofbasic sugar units linked together Monosaccharide – One unit Disaccharides – Two units Oligosaccharides – 10 or fewer units Polysaccharides – Up to 1000 units
Oligosaccharides Raffinose and Stachyose Not broken down by digestive tract Found in dried beans
Polysaccharides Starch Amylose Amylopectin Dextrins Produced when starch molecules are partially brokendown by enzymes, acid, or heat. Less thickening power than starch Glycogen Plant Fiber Components
Plant Fiber Components Called dietary fiber / roughage / bulk Cellulose forms the fiber content in food and is called Roughage.Roughage does not provide any nutrients to our body but it is anessential ingredient of our food as it helps our body to get rid ofundigested food. It mainly consists of Cellulose Hemicellulose Beta-glucans Found in oats and barley Associated with reduced risk of heart disease Pectic substances Pectin forms gels in jams, jellies, and preserves Vegetable gums
ProteinProtein is the basic material of life. It makes up 3/4s ofour body tissue. Without dietary protein, all bodyfunctions would not take place. Proteins can be brokeninto complete and incomplete proteins. Completeproteins supply a sufficient amount of the nineessential amino acids . Animal proteins are called Firstclass proteins because they contains all the essentialamino acids . Plants proteins are called Second classproteins because they do not have all the essentialamino acids. Beans, peas, milk, white portion ofeggs, etc are some examples of proteins.
Composition of protein Protein Contain Carbon Hydrogen Oxygen Nitrogen Potentially also sulfur, phosphorus, iron Large molecules Hundreds or thousands of amino acids joined withpeptide linkage
Protein Structure Primary Long chains Secondary Springlike coiling - Alpha helix Tertiary Folding of coils forming globular shape Quaternary Combining of globular proteins
Protein Quality Amino acids used asbuilding blocks forproteins Nine amino acidsare essential foradult humannutrition Complete proteinsinclude essentialamino acidsIsoleucineLeucineLysineMethioninePhenylalanineThreonineTryptophanValineHistidine
FATSFat is composed of carbon, hydrogen and oxygen. Fats areessential for the proper functioning of the body. We needto consume some fats to remain healthy. Fats supplynecessary fatty acids, acids and glycerol that the body canonly get from foods. Fats also serve as the storagesubstance for the bodys excess calories. When the bodyhas depleted its carbohydrate stores, it draws on fat. Onegram of fats give 9 kilocalories of fats.
Lipids or fats Insoluble in water Feel “greasy” Three major groups Triglycerides Phospholipids Sterols
Triglycerides Account for 90-95 percent of fatty substances in food. Composed of 3 fatty acids linked atoms of carbon with organic acid group One molecule glycerol 3 carbon atoms and three hydroxyl groups
Fatty Acids Most fatty acids in foods are combined intriglycerides. Fatty acids differ Number of hydrogen atoms attached Length of carbon chain Carbon chains Usually even numbered
Types of Fatty Acids Saturated fats No double bonds between carbon atoms, so no morehydrogen can be added Unsaturated Double bonds between some of the carbon atoms thatcan be broken to add hydrogen Monounsaturated One double bond
Omega 3 fatty acids Polyunsaturated fatty acids with double bond between3rd and 4th carbon from the left on the structure. Found in fatty fish Protective for heart disease
Linoleic Acid An essential fatty acid Cannot be made by the body – must be consumed infood
Cis – Trans ConfigurationCis Hydrogen atom on both sides of bondTrans Hydrogen atoms on opposite sides ofbond
Phospholipids Found in food in relatively small amounts Function as emulsifiers One side of molecule attracts fat One side attracts water i.e. Lecithin
Sterols Cholesterol Widely known sterol Found ONLY in animal foods Is associated with coronary heart disease Our bodies also make cholesterol Plant sterols Phytosterols Interfere with absorption of cholesterol
Water Water is essential to human life. Half of our weight is water.The body loses and needs to replace water every day. Thetypical suggestion is 6-8 glasses of liquid every day.Recently reports have come out that you need to drinkenough water to quench your thirst.
Cont… All foods contain at least some water Free water Held inside cells Maintains properties of free water May be removed by pressure Bound water Is part of molecule structure Reduced mobility Does not retain properties of free water
MineralsMinerals act as nutrients and are essential to manyprocesses in the body, including the functioning of theheart and digestive system and bone formation. Somekey minerals we need include Boron, Calcium,Chloride, Chromium, Copper, Iron, Fluoride, Iodine,Magnesium, Manganese , Molybdenum , Phosphorus,Potassium, Selenium, Sodium and Zinc .
VitaminsWithout vitamins, we could not exist . They affect allfunctions in the body and help regulate them. Mostvitamins must be obtained from food. We need 13vitamins: A, C, D, E, K, B (8 different B Vitamins).Vitamins are mainly of two types:- Water-soluble : Band C F at-soluble : A, D, E AND K. Each vitamincarries out specific functions. If your diet is lacking ina certain vitamin, you may develop a deficiency disease