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Components of Food

Components of Food. Chemistry Project 2005-2006. Carbohydrates. Chemistry and Food. What is Carbohydrates ?. Compounds composed of carbon and water General formula C x H 2y O y H:O = 2 : 1 Divided into 3 types ---Monosaccharides ---Disaccharides ---Polysaccharides. Monosaccharides.

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Components of Food

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  1. Components of Food Chemistry Project 2005-2006

  2. Carbohydrates Chemistry and Food

  3. What is Carbohydrates ? • Compounds composed of carbon and water • General formula CxH2yOy • H:O = 2 : 1 • Divided into 3 types • ---Monosaccharides • ---Disaccharides • ---Polysaccharides

  4. Monosaccharides • Eg.---Glucose • Eg.---Fructose • Basic unit of carbohydrates • Sweet in taste, soluble in water • General formula C6H12O6

  5. Disaccharides • Formed from 2 monosaccharides • 2C6H12O6 -----C12H22O11 + H2O • Condensation Maltose Sucrose

  6. Polysaccharides • Condensation polymer of monosaccharides • nC6H12O6--(C6H10O5)n + n(H2O) • Condensation • Example: • ---Starch • ---Cellulose

  7. Open Chain and Ring Structures of Glucose and Fructose

  8. Glycosidic Linkage in Carbohydrates • Bond formed between 2 monosaccharides • Condensation---2 OH group • Removal of H2O

  9. Hydrolysis of Sucrose • Add water • 2 simple sugars • Dilute mineral acids

  10. Hydrolysis of starch (1) • With enzymes • To maltose

  11. Hydrolysis of Starch (2) • Boiled with dilute H2SO4 • To glucose • (C6H10O5)n + nH2O-- nC6H12O6

  12. Reducing and Non-reducing Sugars • Reduces basic solution of Cu2+(aq)or Ag+(aq) • Sugar converted to acid • Aldehyde group • Keto group Fehling’s test

  13. Reducing sugar and Non-reducing sugar

  14. Reducing sugar and Non-reducing sugar

  15. Reducing sugar and Non-reducing sugar

  16. Proteins

  17. Physical properties of proteins • Large Molecular mass ,typically several thousands. eg. hemoglobin :64 500 viral proteins :40 000 000 • Not truly soluble on water,but form colloidal suspension • Constituent element: C,H,O,N may contain S and P • Limitless type of protein e.g. E.coli :800 types human:10 000 types

  18. Vary form species to species Therefore it determines the characteristics of a species • Rarely stored in organisms except in eggs or seeds.

  19. Structure of amino acids • A group of over a hundred members • The commonest are the 20 essential ones,which cannot be synthesized by our bodies.While the rest are non-essential,and can be synthesized from the essential ones.

  20. Zwitterions formation • Basic amino group : -NH2 • Acidic carboxyl group : -COOH • Neutral Amino Acid: no of amino group = no of carboxyl group • Basic Amino Acid: no of amino group > no of carboxyl group • Acidic Amino Acid: no of amino group < no of carboxyl group

  21. Dipolar : with both positive and negative pole • Form zwitterions • Soluble in water but not in organic solvent • Non-volatile, crystalline organic compound with high melting point • Amphoteric : with both acidic and alkaline properties Buffer • Biological significance : Constant Ph for enzymatic reaction

  22. Polypeptide Formation • Amino acid (condensation)dipeptidepolypeptide

  23. Structure of polypeptide • Three dimension • Four types of bonding: a) disulphide bond b) hydrogen bond c) hydrophobic interaction d) ionic bond (broken by alternation in pH)

  24. Level of proteins

  25. Denaturation • Change in shape but not the sequence • Factors: - Heat - Acid - Alkali - high electropositive eg.Ag+ Hg + - high electronegative eg. CN- - organic solvent - Mechanical force

  26. Function of proteins 1.cytoskeleton : cytoplasm consists of a network of fibrous proteins 2. Membrane protein 3. Raw material for growth 4. Formation of enzymes, hormones, antibodies 5. Fibrous proteins for support and protection 6. Osmotic balance and buffering 7. Energy source

  27. Source of proteins • Egg • Milk • Daily products • Soya bean • meat • fish etc…..

  28. Site for protein digestion protein Protease in gastric juice and pancreatic juice Stomach & duodenum peptide Protease in intestinal juice Ileum Amino Acid

  29. Absorption of amino acids Amino acids Capillaries in villi of small intestine Liver

  30. Deamination H H2N-C-COOH carbohydrates H NH2 Urea Kidney for excretion

  31. Deficient disease Kwashiorkor Symptoms of Kwashiorkor: a) Inflammation of skin b) Anaemia c) Swelling of abdomen

  32. Test for Proteins • Protein Turns Yellow Albustix paper green • Biuret test: • Protein + NaOH + CuSO4  purple colouration • (blue) • Identification • Paper chomatography • 2 dimensioned 3 dimenstioned

  33. Fats and Oils!!!

  34. Foods containing Fat and Oils:

  35. What are fats and oils? • Fats and Oils are different lipids. • Lipids are rather diverse class of organic compounds of organic compounds that include triglycerides, phospholipids, steriods, etc. • insoluble in water, soluble in organic solvents. • They are mainly composed of C, H, O but with a very low proportion of oxygen in the molecules.

  36. Structure of fats and oils: • Most natural fats and oils are mixed glycerides. • Glycerides are esters formed from propane-1,2,3-triol (glycerol) and a mixture of different long chain carboxylic acids. • The carboxylic acids(fatty acids) making up fats and oils are usually unbranched, having 14 to 18 carbons. • There are three ester groups per glycerol and the three R groups are usually different, fats and oils are often called triglycerides.

  37. Triglycerides Glycerol A fatty acid

  38. Synthesis of Triglycerides

  39. Microscopic views of fat cells

  40. A more colourful one

  41. Animal fats and Vegetable oils: • Fats and Oils are found in animals and plants. • Animal fats, such as lard and butter, are composed of glycerides rich in heavy chain, saturated fatty acids, Therefore they are solids at room temperatures. • Vegetable oils are liquids because of their high content of glycerides composed of light chain unsaturated fatty acids.

  42. Hydrolytic and Oxidative Rancidity • Fats and Oils develop an unpleasant smell if they are kept for too long. • They are liable to spoilage that produces an ‘off’ odour and a flavour described as rancidity. • Rancidity : -> (1) Hydrolytic (2) Oxidative -> Both of which release foul smelling aldehydes and carboxylic acids.

  43. Hydrolytic rancidity • Presence of moisture in oils, which hydrolyzes the glyceride molecules into propane-1,2,3-triol and free carboxylic acids.

  44. This reaction is speeded up in the presence of certainmicro-organisms or in the presence of some enzymes. • Over a period of time, more molecules of carboxylic acids are liberated which may be volatile and have extremely unpleasant odours and flavours. • At room temperature, hydrolysis proceeds rapidly so that butter soon turns rancid. • So, to duel with, butter is usually covered and refrigerated.

  45. Oxidative Rancidity • Oxidative spoilage occurs when fats/oils are exposed to air and undergo oxidation. • It results in the production of flavours such as ‘tallowy’, A taste of fatty according to “yahoo dictionary”. • Fats and oils with a high degree of unsaturation are more susceptible to oxidation. • The oxidation has a free radical mechanism and is accelerated by trace metals, light and free radical initiators.

  46. Autoxidation

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