Question

If the cooked rice is chewed and tested for starch test, it will show

• A. Positive
• B. Negative
• C. Both
• D. Sometimes only

Answer 1

The correct option is B

Negative

The correct option is (B)

Explanation for the correct option

1. Glucose in plants is stored as starch which is a complex carbohydrate.
2. Starch, when added with iodine solution, changes the color to blue-black.
3. In the oral cavity, a salivary amylase enzyme is present in the saliva, which causes starch breakdown into simple sugars.
4. When chewed food is tested for starch, it will show a negative result because the starch is digested by salivary amylase action.

Explanation for incorrect options

Option (A)

1. The starch test is said to be positive if it detects the presence of starch and turns the iodine solution from red to blue-black.
2. The chewed food will not show positive results as the starch in food is digested by salivary amylase.

Option (C)

1. A test is used to confirm the presence of a substance, agent, or molecule.
2. It can be either positive if it detects the substance's presence or negative if it is absent but cannot be both.

Option (D)

1. A completely chewed food is always starch deficient as all the starch is converted to simple carbohydrates by the action of salivary amylase.
2. Thus, completely chewed food always shows a negative result for starch.

The test will be negative because of the action of salivary amylase breakdown the starch.