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C1 - Food Tests (Reducing sugars - Benedict’s test (Equal volumes of…
C1 - Food Tests
Reducing sugars - Benedict’s test
Equal volumes of Benedict's reagent added
Heated to 70'C in water bath
if non-reducing sugar = present solution will change from
blue
to
brick red
Alkali added (neutralise acid)
Heat solution with HCL to break down monosaccarides
Disaccharides e.g. sucrose are non- reducing - give negative test result
Protein - Biuret test
add equal volume of dilute NaOH to solution + shake
add drops of dilute copper sulphate solution
A blue ring forms at surface which disappears on shaking
if protein = present solution turns lilac purple
Reducing sugars - Benedict’s test
Equal volumes of Benedict's reagent and solution being tested
Heated to 70'C in water bath
if reducing sugar = present solution will change from
blue
to
brick red
Lipids - Emulsion test
mix solution with ethanol in boiling tube + shake
decant in cold water
if lipid = present cloudy white emulsion will form
Starch - Iodine test
Add iodine solution to test solution (10cm3 = 5 drops of iodine
If Starch = present solution will change from
brown
to
blue-black