1 / 39

Principal components of food

Principal components of food. Principal components. Proteins Carbohydrates Fats and oils. Proteins. Function – maintains the structure and proper functioning of all living organisms. Structure – a polymer formed from about 20 amino acids by peptide linkage. COOH. COOH. COOH. H. H.

rhian
Download Presentation

Principal components of food

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Principal components of food

  2. Principal components • Proteins • Carbohydrates • Fats and oils

  3. Proteins • Function – maintains the structure and proper functioning of all living organisms. • Structure – a polymer formed from about 20 amino acids by peptide linkage.

  4. COOH COOH COOH H H H H2N C H2N H2N C C CH3 H CH2COOH 2-Aminopropanoic acid (Alanine) Aminobutanoic acid (Aspartic acid) Aminoethanoic acid (Glycine) Some amino acids

  5. H R H R’ H OH N CH C N CH C OH H O O -H2O H R H R’ N CH C N CH C Peptide linkage O O Peptide linkage

  6. Hydrolysis of proteins • Breaks the peptide linkages in a protein molecule • The composition of the protein molecule may be deduced by using paper chromatography

  7. acid H R H R’ N CH C N CH C H R H R’ O H N CH C N CH C OH O O O Hydrolysis of proteins

  8. Past paper questions • 2001 6c • 2001 6d • 2000 7b

  9. Carbohydrates • Function – provide energy • Formula – Cx H2yOy • Monosaccharides C6H12O6 (glucose, fructose) • Disaccharide C12H22O11 (sucrose, maltose) • Polysaccharides (C6H10O5)n (starch, cellulose)

  10. H H H H H H C O C* C* C* C* H C OH OH OH OH OH Stereoisomers of C6H12O6 4 chiral carbons 24 = 16 stereoisomers

  11. Glucose

  12. Glucose • Open chain (acyclic form) • Two Ring forms (cyclic form) • M.p. 146oC , 150oC • Optical rotations • +112o , +19o +52.7o

  13. Fructose

  14. Reducing sugars

  15. Reducing sugars

  16. Disaccharides

  17. Maltose

  18. Maltose

  19. Sucrose

  20. Polysaccharides • Carbohydrate polymers • Storage polysaccharides • Energy storage – starch and glycogen • Structural polysaccharides • Use to provide protective walls to cells - cellulose

  21. Starch

  22. Cellulose

  23. H+ glucose fructose Hydrolysis of sucrose • Sucrose, like all disaccharides, is hydrolysed by dilute mineral acids to two monosaccharides, glucose and fructose • C12H22O11 + H2O  C6H12O6 + C6H12O6 • The reaction can be effected by enzyme

  24. Hydrolysis of starch • A solution of starch can be hydrolysed in the presence of an enzyme to a disaccharide, maltose. • 2(C6H10O5)n +nH2O  nC12H22O11(maltose) • It starch is boiled with dilute sulphuric acid, it is hydrolyzed to a monosaccharide, glucose. (C6H10O5)n +nH2O  nC6H12O6

  25. Past paper questions • 2001 7c • 2000 6c • 1998 7b

  26. Fats and oils

  27. Triglyceride

  28. Fatty acids

  29. Fatty acid

  30. Fatty acid

  31. Hardening of vegetable oil • Unsaturated oils usually have a lower melting point and exist as a liquid. • Hydrogenation of some of the C=C bonds converts to solid fats. • E.g. Margarine

  32. Hydrolysis of fats and oils • Fats and oils are hydrolysed into carboxylic acid and glycerol in human body. • The substances are then used as fuel, or used in building cell membranes and fatty tissues. • In laboratory, hydrolysis can be carried out in an alkaline medium (i.e. saponification)

  33. Iodine value • Unsaturated fat is considered desirable in our diet. • Iodine value is defined as the number of grams of iodine that reacts with 100 grams of fats/oils.

  34. Rancidity • Rancidity is caused by reactions of fats / oils which release foul smelling aldehydes and fatty acids. • Two types: • Hydrolytic rancidity • Oxidative rancidity

  35. Hydrolytic rancidity • Occurs as a result of hydrolysis of glyceride molecules to glyerol and free carboxylic acids by the presence of moisture in the oils. • E.g. Frying of chips in oil at high temp. • The reaction is speeded up in the presence of certain micro-organisms or enzymes.

  36. Oxidative rancidity • Occurs when fats/oils are exposed to air and undergo oxidation. • Fats/oils have a high degree of unsaturation are more susceptible to oxidation. • The oxidation is a free radical mechanism and is accelerated by trace metals, light and free radical initiators.

  37. Past paper questions • 2000 6a • 1999 7d

More Related