The method of distinguishing fat and starch in food: slide and squeeze the food on white paper, leaving oil stains on the white paper to prove that the food contains fat; Dropping iodine into food will turn the food dark blue, which proves that the food contains starch.

Fat is an important part of human body and the nutrient with the highest calorie content. It is an essential substance for the establishment, transformation and growth of cells in vivo. The main function of fat is to supply heat. Starch is an important part of food, so it feels a little sweet to chew rice. This is because amylase in saliva hydrolyzes starch into disaccharide-maltose. After food enters the gastrointestinal tract, it can also be hydrolyzed by salivary amylase secreted by the pancreas, and the formed glucose is absorbed by the small intestine wall and becomes a nutrient for human tissues.