Question

What should you use to test if a type of food has starch, sugar or fat?

Answer 1

Iodine solution for starch, Benedict's solution for reducing sugars, and ethanol solution for fats.

Explanation:

For the starch test, we use a solution of iodine. If iodine is added to a solution where starch is present, the iodine goes from brown to black-blue, indicating a positive test rule. Here is a picture:

For the reducing sugars test, we use Benedict's solution. Benedict's solution is composed of sodium carbonate `(Na_2CO_3)`, sodium citrate `(NaC_6H_7O_7)` and copper(II) sulfate pentahydrate `(CuSO_4*5H_2O)`.

When we add Benedict's solution to a solution, it can form many different colours. If no sugars are present, it will be blue. If there are a lot of sugars present, it will turn red. Here is a picture of the test:

To test for fats, we must use an ethanol `(C_2H_5OH)` solution. We add ethanol to a sample solution and shake it. After that, we must pour in some water. If a cloudy white emulsion appears, then the test is positive, and lipids (fats) are present. If nothing happens, then the test is negative, and no fats are present. Again, here is a picture of the test:

I hope this helps!