Methods:
A serial dilution of starch solution is made as follows:
Place 5 clean test tubes in a test tube rack.
Place 10 cm³ of 1٪ starch solution in the first test tube by using a measuring cylinder.
1 cm³ of the solution has been taken out from the first test tube and place it in the second test tube by using a syringe.
9 cm³ of water is added into the second test tube using a measuring cylinder and stir it with a glass rod. The 1 cm³ of 1٪ starch solution is now dilute to 0.1٪ solution.
1 cm³ of this 0.1٪ starch solution has now been transfer from the second test tube to the third test tube.
Add 9 cm³ of water into the third test tube. This solution is now become 0.01٪ solution.
1 cm³ solution has been transfer from the third test tube to the fourth test tube and added 9 cm³ of water to make a 0.001٪ solution.
Repeat the steps for the fifth test tube to make a 0.0001٪ solution.
1 cm³ of this solution is now removed from the fifth test tube to make the test same.
1 drop of iodine solution is added to each test tube and stir it with a glass rod.
The observation is recorded at the table 1.1.
(B)
Place 4 clean test tubes in a test tube rack.
2 cm³ of the starch solution has been taken out from the starch solution and place it in the first test tube by using a syringe.
18 cm³ of water is added into the test tube using a measuring cylinder and stir it with a glass rod. The 2 cm³ of 1٪ starch solution is now dilute to 0.01٪ solution.
The other test tubes is fill with the following solution:
1 drop of iodine solution is added to each test tube and stir it with a glass rod.
The observation is recorded at the table 1.2.
Results:
Table 1.1
Table 1.2
Discussion:
As I increase the molarity of starch, there will have only some minor change on the solution. This is because the starch solution has been diluted for many times. Starch is a polysaccharide, consisting of glucose units joined together by glycosidic bonds. The chains formed during the condensation reaction are either linear or highly branched molecules.
Conclusion:
My hypothesis was stating that starch is a polysaccharide which is found in cereals like rice and in tubers like potato. Iodine test for starch is the most followed method to analyse the presence of starch in the given food material. When iodine solution is mixed with starch it turns from brown to dark blue. As this happens with very small amounts of starch, iodine test is a sensitive one. Iodine solution penetrates into the starch most easily when the cell walls have been destroyed and it reacts most readily when the starch grains are swollen.
Citation: