1.4.6

Starch

Test yourself

Starch

Starch is a carbohydrate and an important part of a balanced diet. Starch is insoluble in water and alcohol.

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Appearance

  • Starch is solid at room temperature.
    • Starch is insoluble in water and alcohol.
    • Starch is oderless and tasteless.
  • Starch is a natural carbohydrate polymer.
    • Starch is made up of repeating glucose monomers.
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Foods rich in starch

  • Foods that are very rich in starch include:
    • Wheat
    • Potatoes
    • Maize
    • Rice
    • Corn
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Uses

  • Starch has many uses in food.
    • Processing starch produces sugars that can be added to foods.
    • Starch is used in brewing and fermenting beer and whiskey.
    • Mixing starch with warm water can produce wheatpaste.
    • Wheatpaste is used as a thickening agent.
  • Starch stiffens and hardens clothes if added before ironing.
    • The word 'starch' is sometimes used to mean 'to stiffen and strengthen.'
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Testing for starch

  • Iodine is used to test for starch.
  • Plants use energy from the sun to convert water and carbon dioxide into oxygen and glucose.
    • This process is called photosynthesis.
    • Glucose is converted to starch and used to build cell walls.
    • Starch is also found in seeds.
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Testing for starch practical

  • Boil a leaf in water and ethanol, then drop some iodine onto it.
    • Watch for the orange-coloured iodine to change to a blue-black colour.
  • If the colour changes, that means starch is present.
    • The presence of starch is evidence of photosynthesis.
  • If there is no starch, then the iodine will remain orange.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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