Required practical 4 - food tests

what is a reagent

a chemical solution or substance added to a sample to test for the presence of a specific biological molecule

Reagant for starch test

iodine solution

method to test for starch

• put food on a spotting tile

• add iodine onto food sample

positive result for starch

brown - blue/black

negative result for starch

remains brown

reagent for glucose

benedicts solution

method for glucose test

• Add Benedict's solution to the food sample in a boiling tube

• Heat in water bath ( 95 degrees )

positive result for glucose

blue - red, yellow

negative result for glucose

remains blue

reagent to test for protein

biurets solution

method to test for protein

• put food sample in a boiling tube

• add biuret reagent to the sample

positive result for protein

blue - purple

negative result for protein

remains blue

reagent for lipids test

ethanol

method to test for lipid

• put food sample into boiling tube

• add ethanol

• shake well

• remove the filtrate and add to a test tube of water

positive result for lipids

cloudy emulsion

negative result for lipids

clear