Can anyone explain about test of starch?

Question

Answer

Test leaves for the presence of starch,the leaf is boiled in water and then the boiled leaf is placed in a boiling tube containing 90% ethanol (ethyl alcohol). The ethanol boils and the green colouring (chlorophyll) is removed from the leaf. The iodine reagent is then added, which causes the green areas on the leaf, where starch is supposedly present, to turn to a blue-black colour. This indicates the presence of starch in the leaf.

Answer

The iodine–starch test is a chemical reaction that is used to test for the presence of starch or for iodine. The combination of starch and iodine is intensely blue-black

Answer

Test of Starch

Starch is a complex carbohydrate that is commonly found in plants. It serves as a major source of energy for both plants and animals. To determine the presence of starch in a substance, several tests can be conducted.

Iodine Test

One of the most commonly used tests for starch is the iodine test. Iodine reacts with the starch molecules and forms a dark blue-black color complex. The steps for the iodine test are as follows:

1. Take a small amount of the substance to be tested in a test tube or on a white tile.
2. Add a few drops of iodine solution to the substance.
3. Observe the color change. If the substance contains starch, it will turn dark blue-black.

Saliva Test

Another simple test for starch can be performed using saliva. Saliva contains an enzyme called amylase, which breaks down starch into simpler sugars. The steps for the saliva test are as follows:

1. Take a small amount of the substance to be tested in a test tube or on a white tile.
2. Add a few drops of saliva to the substance and mix well.
3. Allow the mixture to sit for a few minutes.
4. Add a few drops of iodine solution to the mixture.
5. Observe the color change. If the substance contains starch, it will turn dark blue-black. If the starch has been broken down by amylase, the color change will be less intense or may not occur at all.

Boiling Water Test

The boiling water test is another simple method to test for the presence of starch. The steps for this test are as follows:

1. Take a small amount of the substance to be tested in a test tube or on a white tile.
2. Add a few drops of water to the substance and mix well.
3. Place the test tube or tile in a boiling water bath for a few minutes.
4. Remove the test tube or tile from the boiling water bath and allow it to cool.
5. Add a few drops of iodine solution to the mixture.
6. Observe the color change. If the substance contains starch, it will turn dark blue-black.

Conclusion

By performing these tests, the presence of starch can be determined. The iodine test is the most commonly used method, as it provides a clear and distinct color change. The saliva test and boiling water test can also be used as alternative methods. These tests are useful in various fields, including food science, biology, and chemistry.

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