Carbohydrates

Definition
1. Consist of polyhydroxy aldehydes or ketones
2. 3 Elements: C - Carbon, H- Hydrogen & O - Oxygen
Importance
1. Source of energy
  1. Glucose
  2. Starch in plants
2. Building blocks
  1. Plant : Cellulose
  2. Human : Glycogen
3. Components of other molecules
  1. DNA
  2. RNA
  3. Glycolipids
Monosaccharides
1. Aldose/Ketose
2. No. of carbons in chain
3. Chiral carbon
  1. Fisher Projections
    1. Ways to represent mirror image in 2 dimensions
  2. Chiral objects
    1. Cannot be superimposed on their mirror image
      1. Hand
      2. Gloves
  3. Archiral objects
    1. Can be superimposed on the mirror images
      1. Drinking glass
      2. Cubes
Classification of CHO
1. Monosaccharides
  1. 1 polyhydroxy aldehyde/ketone
    1. Glucose
    2. Xylose
  2. Single sugars
  3. Colorless, water-soluble & crystalline solids
  4. Sweet taste
  5. Glucose Anomers
    1. Forms are anomers of each other & carbon-1 called the anomeric carbon
  6. Fructose Anomers
    1. Closes on itself to form a furanose ring
  7. Importance
    1. β-D-glucose
      1. dextrose & blood sugar
      2. Metabolized in the body for energy
      3. Other sugar : must be converted to glucose by the liver
    2. β-D-fructose
      1. levulose & fruit sugar
      2. Sweetest
    3. β-D-ribose
      1. ribonucleic acid (RNA)
    4. β-D-galactose
      1. Glucose into lactose
    5. β-D-deoxyribose
      1. deoxyribonucleic acid (DNA)
2. Disaccharides
  1. 2 monosaccharides
  2. Glycosidic Bonds
    1. Covalent bond that joins a carbohydrate to another group
  3. Importance
    1. Sucrose
      1. Table sugar
      2. Caramel formed from heating sucrose
      3. Invert sugar : produced by hydrolysis of sucrose under acidic conditions
    2. Maltose
      1. Malt sugar
      2. Produced in germinating grain
      3. Formed during the hydrolysis of starch to glucose during digestion
    3. Lactose
      1. Milk sugar
      2. Digested by enzyme lactase
3. Polysaccharides
  1. More than 2
  2. Starch
    1. Polymer consisting of D-glucose units
    2. Amylose
      1. Long, unbranched chains of glucose
      2. Flexible to allow the molecule to twist into the shape of helix
    3. Amylopectin
      1. Long chains of glucose
    4. Glycogen
      1. Animal starch
      2. Abundant in the liver & muscles
      3. Maintains normal blood sugar level & gives energy
    5. Cellulose
      1. Long,unbranched chains of D-glucose connected by β(1→4) glycosidic
      2. Important structural
    6. Chitin
      1. Polymer of N-acetylglucosamine
      2. Extremely strong
4. Oligosaccharides
  1. 3 - 10 monosaccharides
  2. Raffinose
    1. Trisaccharide
      1. Galactose
      2. Fructose
      3. Glucose
    2. Found in beans, cabbage, broccoli etc
    3. Hydrolyzed to D-galactose & sucrose by the enzyme α-galactosidase
Dietary Fiber
1. Important
2. Complex mixture
3. Resistant to hydrolysis by endogenous enzymes
4. Types
  1. Cellulose
    1. Insoluble in water
    2. Low-calores foods : bulking & rheological
    3. Linear polymer of glucose with beta : 1-4 links
  2. Beta-Glucans
    1. Glucose polymers contains both beta : 1-3 links & beta 1-4 links
    2. Less linear, more soluble than cellulose
    3. Contribute viscosity of products
  3. Lignin
    1. High complex nonpolysaccharide
    2. Insoluble
  4. Pectins
    1. Polymer galacturonic acid bounded by alpha : 1-4 galacturonic links
    2. Produce strong gels
  5. Hemicellulose
    1. Heterogenous
    2. Different sugars in backbone & side chain
    3. Soluble in dilute alkali
    4. Improve water binding in baked goods
  6. Chitin/Chitosan
    1. Poly beta, 1-4 acetyl-D-glucosamine
    2. Cellulose-like constituents
    3. Deacetylation of chitin = chitosan
  7. Plant Gums
    1. Water-soluble polysaccharides
    2. Contribute : viscosity/gelling properties
    3. Thickening agents
Oxidation Reaction
1. Test for reducing sugars
2. See colour changes
3. Formation of sugar alcohol
Interaction with water
1. Sucrose with water become solubilize
2. Starch with water won't be solubilize
  1. Apply heat/ stir it to increase the solubility rate
    1. Colour changes from opaque to translucent
Retrogradation of amylose
Syneresis
1. Water will be secreted from the carbohydrate
Hydrolysis
1. Preservation techniques
Browning reactions
1. Enzymatic: Oxygen + Phenolic + PPO
2. Nonenzymatic: Caramelization
Caramelization
1. Process
  1. Direct heating
  2. Anomeric shifts, alteration of ring size & breakage of glycosidic bonds
  3. Dehydration
  4. Formation of anhydro rings, double band formation
  5. Color & flavour
2. Influenced by pH
Maillard Browning
1. Carbohydrate + Protein
2. Why we need to control
  1. Loss of amino acid
  2. Dark colour, strong flavour & odour
  3. Toxicity of product
Pyrolysis
1. Total loss of water from sugar molecule
2. Ex: Burnt & inedible flavor

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Carbohydrates

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	Created by Syarifah Sumaira over 5 years ago