Food tests

Question 1

Test for sugars (glucose)

Answer 1

Place food in (blue) Benedict’s solution
Heat in water bath
Benedict’s solution will change colour (green, yellow, orange, red or brown) if sugar is present
Benedict’s solution is an irritant

Question 2

Test for starch

Answer 2

(brown-orange) Iodine added to food
Food will change blue-black if containing starch
Iodine is an irritant

Question 3

Test for proteins

Answer 3

Biuret reagent test
Add biuret solution A to food solution and biuret solution B, then shake
The solution will turn purple, or have a purple ring between layers if protein is present
Biuret A is corrosive
Biuret B is an irritant

Question 4

Test for lipids (emulsion test)

Answer 4

ethanol is added to a test tube containing crushed food
The liquid is poured into a second test tube containing water, leaving any food residue behind.
A positive result will result in a cloudy liquid
Ethanol is flammable