FOOD TESTS

Name of test: Benedict's test
Test for ...?: Reducing sugar
Reagent: Benedict's solution [Copper (II) Sulphate]
Procedures:
1. Solution of 2cm3 Benedict's solution in test tube.
2. Shake mixture and immerse in boiling water.
3. Observe colours:
red precipitate - highest amount of reducing sugar present
orange precipitate
yellow precipitate
green precipitate
blue percipitate - lowest/no amount reducing sugar present
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Name of test: Ethanol emulsion test
Test for ...?: Fats (liquid)
Reagent: ethanol
Procedures:
1. 2cm3 of ethanol in test tube
2. Shake mixture
3. add 2cm3 of distilled water
Results:
- Heat felt
- mixture becomes white/milky/cloudy
= fats PRESENT
- No heat felt
- mixture stays translucent
= fats ABSENT
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Name of test: Oil spot test
Test for ...?: Fats (solid)Reagent: rien (French: nothing)Procedures:
1. wrap food in filter paper
2. crush by pestle
Results
- If it leaves a translucent spot on filter paper
= fats PRESENT
- If leaves no translucent spot
= fats ABSENT
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Name of test: Biuret test
Test for : Proteins
Reagents:
- sodium hydroxide
- 1% copper (II) sulphate
Procedures:
1. add 1cm3 sodium hydroxide
2. shake THROUGHLY
3. add 1% copper (II) sulphate
DROP BY DROP
SHAKING AFTER EACH DROP
Results:
Violet = highest amount of proteins
Blue = low/no proteins present