Food Tests Methodology

Testing for reducing sugars (4)

Benedicts test

Mix sample with distilled water using pestle and mortar and filter to create filtrate

Mixed filtrate with benedicts solution and heat in water bath

Solution will turn from blue - green - yellow - orange - brick red, depending on concentration of R sugars

Testing for non-reducing sugars (4)

Benedicts test + HCl (carried out after first benedicts test)

Add HCl to the filtrate and heat to allow disaccharides to break down into NR monosaccharides

Add sodium hydrogen carbonate and use litmus paper to determine neutralisation point

Add benedicts solution and heat again - solution will turn from blue - green - yellow - orange - brick red depending on concentration on NR sugar

Test for lipids (4)

Emulsion test

Add sample to test tube with ethanol and add a bung and shake for at least 1 minute

Add distilled water to the test tube and shake it again

Leave to sit - if lipids present a cloudy white emulsion will form on top

Testing for starch (3)

Iodine test

Add iodine solution to filtrate

If starch is present, solution turns from orange-brown to blue-black

Testing for Proteins (3)

Biuret Reagant test

Add reagant to solution of sample mixed with water

If protein is present, solution turns from blue to lilac