(a) State two effects of heat on starch when food is cooked. [2] (b) Explain what happens when starch is used to thicken a sauce. [4] (c) Describe a method ...
Question 1 Report
(a) State two effects of heat on starch when food is cooked. [2]
(b) Explain what happens when starch is used to thicken a sauce. [4]
(c) Describe a method of making a smooth white sauce using flour and milk. [6]
Answer Details
(a) State two effects of heat on starch. [2]
One mark each (max 2):
- Starch granules absorb water and swell when heated in a liquid (gelatinisation) (1)
- Starch turns brown when heated to a high temperature without water (dextrinisation), e.g. toast or pastry crust (1)
(b) Explain what happens when starch thickens a sauce. [4]
One mark for each valid point (max 4):
- When flour is mixed with a liquid and heated, the starch granules begin to absorb the liquid (1)
- As the temperature rises, the granules swell and burst (1)
- The starch molecules spread out into the liquid, making it thicker (gelatinisation) (1)
- The sauce must be stirred to prevent lumps from forming and to ensure even thickening (1)
(c) Describe a method of making a smooth white sauce. [6]
One mark for each step (max 6):
- Melt a measured amount of butter or margarine in a saucepan over a low heat (1)
- Remove from the heat and stir in the flour to form a smooth paste (roux) (1)
- Return to the heat and cook for one minute, stirring (1)
- Gradually add the milk, a little at a time, stirring well after each addition (1)
- Bring to the boil, still stirring, until the sauce thickens (1)
- Season with salt and pepper (1)
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