Iodine solution can be used to test the presence of starch in food items. If starch is present, it turns in to blue-black colour on the addition of iodine

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.

Subtract the fiber from the total carb count. The result is the amount of net carbs in a serving. Net carbs correspond to the amount of carbohydrates able to raise your blood sugar level. In other words, net carbs correspond to the amount of sugars and starches per serving. In the case of the canned red kidney beans, subtract the 14 grams of fiber from the 40 grams of total carbs to obtain 26 grams of net carbs.

Add iodine in the food sample...if it turns blue-black it signifies the presence of starch