Test for Starch

What is Starch?

Starch is a white, granular and organic substance produced by plants. It is a soft and tasteless powder which is not soluble in alcohol, cold water and other solvents. The basic chemical formula of any molecule of starch is C6H10O5.

A simple test for starch performed at a lab or home can allow students to understand the type of carbohydrate their foods contain.

Production of Starch

Starch is produced within the green leaves of plants from the excess glucose created during photosynthesis. The primary purpose of starch is to act as a reserve food supply for plants. 

Furthermore, plants store starch in chloroplasts as granules and other organs such as roots, stem, seeds, tuber, etc. Some prominent examples of foods that contain starch are potatoes, corn, wheat, rice, cassava, etc. 

Additionally, this starch is disintegrated with the help of various enzymes and water. This process converts starch into monomer glucose units. It diffuses from the cells and nourishes plant tissues. On the other hand, in case of human and other animals, starch is broken down into sugar molecules. It supplies the necessary energy.

Before moving onto the topic of how to test for starch, here are some common questions for students to solve –

  1. What is starch?

  2. What is the chemical formula of starch?

  3. Where do plants store starch?

  4. What is the purpose of starch?

Chemical Test for Starch

A simple chemical test containing iodine is often performed to determine the presence of carbohydrate in a food item. Food items consumed by individuals contains different types of carbohydrate, and starch is one of them. This simple iodine test for starch can assist in this purpose.

  • Test 1: test for starch in a potato

In this test, students can check the amount of starch in a potato. However, for this test, they need some equipment. These are potatoes, a knife, a clean pot, and iodine solution for starch test. 

At first, peel the potato and cut it into small pieces. After that, place these small pieces inside the clean pot and add 2-3 drops of iodine solution. Then keep the bowl undisturbed for a couple of minutes to see the change.

Furthermore, if followed correctly, the iodine test for starch results will show that the slices of potatoes have developed a black-blue colour.

  • Test 2: liquid test for starch iodine test

This simple test for starch can be successfully performed using any liquid food sample. The equipment and ingredients required for this test are test tubes, liquid food sample, and iodine sample.

In the beginning, pour around 10 ml of food sample in a clean test tube. After that, add around 4-5 drops of iodine solution into the liquid. Then wait to observe the results, if it turns blue then that food item contains starch.

These food test for starch are simple, and students can take it up as a DIY project.

  • Test 3: leave testing for starch

Similar to the tests mentioned above, this test will also indicate the presence of starch. For this test students need, a fresh green leaf, around 250ml of water, a boiling pot and a test tube, ethanol and iodine solution.

To begin with, students should boil the water first and then place the leaf into it for two minutes. After that, remove the leaf from there and place it in a test tube containing 90% ethanol. Now, boil this solution for 10 minutes and rinse the leaf in cold water afterwards. 

After that, place this leaf on a clean tile and add a few drops of iodine solution. If it turns blue-black, it contains starch.

For more information on other topics of biology besides this simple test for starch, students can go through the rest of the website. The app allows students to access more study materials, and they can join online live classes as well. The subject experts are covering a new topic every day.

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FAQ (Frequently Asked Questions)

1. How do we test for starch?

We can test for starch with the help of an iodine test. Soak any food items, namely potato, in drops of iodine for some time. If it turns blue-black afterwards, it contains starch. 

2. What is the liquid used for testing starch

The liquid used for testing starch is an iodine solution. Place a few drops of this liquid on solid and liquid food items and observe the results. Is the food item becomes black-blue, this test is positive.

3. Iodine test is used to detect what?

Iodine test is used to detect the existence of carbohydrate in food items. Food items contain various types of carbohydrate, and starch is an example of it. This test enables individuals to understand the presence of starch in a food item.