Food tests

Question 1

How would you test for Starch?

Answer 1

Use iodine solution+shake and if present it should change to blue-black

Question 2

How would you test for reducing sugars?

Answer 2

Add Benedicts reagent and heat it in a water bath. If present a colour change of blue,green,yellow,orange/red should happen

Question 3

How would you test for non-reducing sugars?

Answer 3

Test for reducing sugars to make sure there’s none, solution should stay blue under heat w benedict reagent. Then add acid(HCl) and boil to break down the solution into monosacharides. Cool down the solution and add an alkali to neutralise. Then redo reducing sugar test to get red solution if positive. this showing it was a non-reducing sugar before

Question 4

How would you test for lipids?

Answer 4

The emulsion test: Mix with ethanol. Add ethanol solution into water. If cloudy white emulsion lipid is present

Question 5

How would you test for Proteins?

Answer 5

The Biuret test: Add sodium hydroxide solution, then add copper sulfate solution. if present should turn purple