Food Tests

starch test

grind food sample with 2cm3 of distilled water, add a few drops of iodine

starch positive result

orange → blue/black

reducing sugar test

add benedict’s reagent with crushed food sample and heat in a water bath at 75 degrees - only works on reducing sugars

reducing sugar positive result

blue → green → yellow → red

protein test

2cm3 food solution, 2m3 biuret solution

protein positive result

blue → lilac

lipids test

2cm3 food solution + few drops of ethanol shake, + few drops of distilled water, shake

positive lipids result

colourless → white cloudy emulsion

non-reducing sugar

2cm3 food sample + 2cm3 Benedict's reagent, heat in water bath 75 degrees. does not change colour - not a reducing sugar. 2cm3 food sample to HCl in 75 degree water bath. slowly add sodium hydrogencarbonate to neutralise acid. redo Benedict’s test → brown/red

potassium iodide (iodine in it)

starch grains in a plant cell