Food Tests: Chapter 5 - Nutrition

Hmm... I'm not sure what I wanted to revise today, so I'll just pick Food Tests!

So it will be rolled out in the following format:

Name of test:

Test for ...?:

Reagent(s):

Procedures:

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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 emmersion 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

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Name of test: Iodine test
Test for ...?: Starch
Reagents: iodine solution (duh.. obviously =p)

1. Drop drops of iodine sol. on food

dark blue = starch present

yellowish-brown = starch absent