Find out a qualitative test for proteins, fats and oils, amino acids and test any fruit juice, saliva, sweat and urine for them.

Item

Name of the test

Procedure

Result

Inference

1.

Fruit juice

Biuret’s test

Fruit juice + Biuret’s reagent

Colour changes from light blue to purple

Protein is present.

Grease test

To a brown paper, add a few drops of fruit juice.

No translucent spot

Fats and oils are absent or are in negligible amounts.

Ninhydrin test

Fruit juice + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour

Amino acids are present.

2.

Saliva

Biuret’s test

Saliva + Biuret’s reagent

Colour changes from light blue to purple

Proteins are present.

Grease test

On a brown paper, add a drop of saliva.

No translucent spot

Fats/oils are absent.

Ninhydrin test

Saliva + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour

Amino acids are present.

3.

Sweat

Biuret’s test

Sweat + Biuret’s reagent

No colour change

Proteins are absent.

Solubility test

Sweat + Water

Oily appearance

Fats/oil may be present.

Ninhydrin test

Sweat + Ninhydrin reagent + boil for 5 minutes

No colour change, solution remains colourless

Amino acids are absent.

4.

Urine

Biuret’s test

Few drops of urine + Biuret’s reagent

Colour changes from light blue to purple

Proteins are present.

Solubility test

Few drops of urine + Water

Little bit of oily appearance

Fats may or may not be present.

Ninhydrin test

Few drops of urine + Ninhydrin reagent + boil for 5 minutes

Colourless solution changes to pink, blue, or purple colour depending on the type of amino acid

Amino acids are present.