The Chemistry of Food:

Carbohydrates:

• Consist of carbon, hydrogen and oxygen

• Are made up of sugars, e.g. glucose -

  • single sugar

  • C6H12O6

• Complex carbohydrates -

  • such as starch and cellulose

    • cellulose is used as support in plants

  • are long chains of simple single units

Lipids:

• Consist of carbon, hydrogen and oxygen

• Fats and oils

• The most efficient energy store

• Can be combined to create hormones and are used in the nervous system

• Insoluble in water

• Made up of 3 molecules of fatty acids chemically joined to 1 molecule of glycerol

  • The glycerol molecule always is the same

  • The fatty acids can vary

    • This determines whether the lipid is a solid or a liquid

Proteins:

• Consist of carbon, hydrogen, oxygen and nitrogen

• Used for building cells and tissues

• Are the basis for enzymes

• Act as muscles, tendons, insulin, antibodies, enzymes and catalysts

• Make up around 15%-16% of the human body

• Found in meat, fish, pulses and cheese

• Long chains of amino acids

• Bonds are sensitive to pH levels and temperature

Food Tests:

Carbohydrates:

• Iodine test for starch -

  • Yellow / red iodine turns blue / black in the presence of starch

• Benedict’s solution test for sugars -

  • Blue Benedict’s solution turns brick red when heated in the presence of sugars

Lipids:

• Ethanol test for lipids -

  • Colourless ethanol turns cloudy white in the presence of lipids

Proteins:

• Biuret solution test for proteins -

  • Blue Biuret solution turns purple in the presence of proteins