how to find starch in food
Answers
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Answer:
Starch is the most common carbohydrate in the human diet and is contained in many staple foods. The major sources of starch intake worldwide are cereals (rice, wheat, and maize) and root vegetables (potatoes and cassava). We can use iodine solution to test for the presence of starch. If starch is present is a food item, it turns blue-black colour when iodine solution is added to it.
Explanation:
The Iodine Test for Starch is used to determine the presence of starch in biological materials:
The procedure for the iodine test for starch depends on whether the test sample is a solid or liquid.
SOLID SAMPLE
Peel off the skin of any vegetables e.g. potato and fruits as these are often impermeable. Use a clean spatula to remove samples of powdered food. Avoid cross contamination with other foods.
Add a few ( 2-3) drops of bench iodine solution potassium to a piece of solid food on a white tile.
Make observations.
LIQUID SAMPLE
Add 10 cm3 of the liquid food sample to a clean, dry test tube.
Add about 5 drops of iodine solution to the test tube.
Note any colour changes.
To prepare a control, perform steps 1 -3 for de-ionized water.
OBSERVATIONS / RESULTS
if there is No change (Iodine remains brown)- Starch is not present
If a blue-black colour develops- Starch is present
Starch is a storage molecule found only in plants. Only plants and plant-based foods should test positive for the presence of starch. Any animal product testing positive for starch may be contaminated or mixed with plant product.
Note that the iodine test for starch cannot be performed on very dark solids or liquids which do not permit the observation of a colour change. Results of such an experiment are inconclusive