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PRACTICAL 1 Food Test (Chemical Test for Carbohydrate, Lipids and Proteins)

Aim: Determine the presence of carbohydrate, lipids and proteins in food

Procedure:
1
...
Determine if the following
foods contain starch; bread, rice, onion, potato, milk powder, cornflakes, apple
...

2
...
Shake the
mixture well
...
Pour
the mixture from the first test tube into this second test tube
...

(b) Grease-spot test
Add a drop of oil onto a piece of filter paper against a light
...

(c) Sudan III
I
...
Then add 2-5 drops of
Sudan red to the mix
...


II
...

If lipid is present in the sample, oil or droplets will be released from the
tissue and float on the water surface
...
Leave the sample for a few minutes
...


3
...
Add 1-2 drops of copper sulfate (CuSO4) solution and shake to mix
well
...


4
...

(b) Using the same procedure, test the presence of reducing sugar in the
food samples apple and papaya
...
Iodine test for starch

Food sample

Starch present (Y/N)

Bread

Y

Rice

Y

Onion

N

Potato

Y

Milk powder

N

Cornflakes

Y

Apple

N

2
...


(b) Grease-spot test
*Provide labelled drawing of the observation
...
Biuret Test

Sample

Protein present (Y/N)

Sausage

Y

Egg yolk

Y

Oil

N

Cheese

N

Milk powder

Y

4
...
Comment on the contents of the food samples and suggest what type of food
is healthy
...
Overconsumption of this food can lead to diabetes, heart disease
and weight gain since they can cause the blood sugar level to spike rapidly and fall sharply
...
Lipids also provide protection to internal organs
such as kidneys
...
Food containing protein such as sausage, egg yolk and milk powder can help to build
muscle mass and promote the contraction and relaxation of the muscle
...
Apples and papaya contain
low carbohydrates and are a good source of fibres and vitamins such as vitamin A, vitamin E
and vitamin B-complex
...
This is because eating too much
can lead to malnutrition and overconsumption can lead to health complications
...
Using your data and your understanding of nutrition, which of the substances
would provide the best fuel for your body to endure a marathon? Explain
...
Foods that contain carbohydrates are bread, rice, potato and cornflakes
are ideal for short term energy
...
This is because they can be broken down easily to form glucose and are used
to produce energy in the form of ATP
...
Foods that contain lipids are butter and cheese are ideal for long
term energy because one gram of lipid contains twice the amount of one gram of
carbohydrates
...
Lipids act as a
backup source of fuel when carbohydrates are depleted
...


Conclusion: Carbohydrates, lipids and proteins in food are tested and determined by iodine
test, emulsion test, grease-spot test, Sudan III, biuret test and benedict’s test
...
In the iodine test, only bread, rice, potato and cornflakes contain starch
...
In the
emulsion test, ethanol, distilled water and cooking oil are mixed and shaken
...
In the grease-spot test, the appearance
of a translucent spot on the filter paper shows that there is the presence of lipids
...
Sausage, egg yolk and milk powder
are tested for containing protein using the biuret test
...
Apple
and papaya are tested to be reducing sugar
...

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