Page 51 - Biology_F5

Biology for Advanced Level Secondary Schools

Table 1.3: Test for starch, reducing sugar and non-reducing sugar

Food
sample to be Procedure Observation Inference
tested
Starch Iodine test Blue-black colouration is Starch is
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observed present
Place 2 ml of 1% starch
solution in a clean and dry
test tube
Add 3 drops of iodine
solution (No heating is
required)
Alternatively, add the Iodine
solution to the solid form of
starch

Observe what happens for
about 1 to 3 minutes

Reducing Benedict’s test The initial blue Reducing
sugar colouration of the sugar is

Place 2 ml of a solution present
containing reducing sugar in mixture turns green,
a clean and dry test tube then yellowish to
orange and may finally

Add 2 ml of Benedict’s form a brick- red
solution, and heat gently to precipitate
boil for about 2 minutes

Non- Place 2 ml of non- reducing The initial blue Non –
reducing sugar (such as sucrose) colouration of the reducing sugar
sugar solution in a clean and dry mixture turns green, then is present
test-tube yellowish to orange and

Add 1ml dilute hydrochloric may finally form a brick-
acid, heat gently, then allow to red precipitate
cool
Carefully, neutralise with 1 ml
of sodium hydroxide solution

Add 2 ml of Benedict’s
solution and heat to boil

for about 2 minutes

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