Starch is also called starch in the catering industry, and the two are the same thing.

Starch is a carbohydrate formed by plants through photosynthesis. It is a polysaccharide composed of a single type of sugar unit and is naturally synthesized by plants. Starch is found in large amounts in the seeds, tubers and roots of plants.

The starch used for thickening, also called dough, is a polysaccharide polymer formed by the condensation of multiple glucose molecules. Starch is insoluble in water and gelatinizes into a colloid when heated to 6°C with water. The solution allows vegetables to be heated indirectly, protecting the nutrients of the food and improving the taste. The lost nutrients can be eaten together with the thick soup.