Which technique involves the thickening of a sauce by heating starch grains?

The technique that involves thickening a sauce by heating starch grains is gelatinisation. When starch is heated in the presence of liquid, the heat causes the starch granules to absorb water and swell. This process leads to the thickening of the sauce as the starch granules disrupt and release their molecules into the mixture, creating a gel-like consistency.

This technique is fundamental in cooking and is widely used in various recipes, especially sauces, gravies, and puddings. The transformation of the starch from a dry powder to a thickened, smooth texture illustrates the importance of heat and moisture in food preparation.

The other options involve different processes: coagulation refers to the transformation of proteins from a liquid to a solid state, sweetening involves the addition or enhancement of sweetness, and emulsification relates to the mixing of two immiscible liquids, such as oil and water. Understanding the distinction between these processes helps clarify how various cooking techniques affect texture and consistency in food.