Define gelatinization and its role in custards and fillings.

• A. Starch granules absorb water and swell when heated, thickening the mixture.
• B. Proteins coagulate to set.
• C. Fats melt to thin the mixture.
• D. Gases cause expansion.

Answer: (A)

Gelatinization is the process where starch granules absorb water and swell as heat is applied, forming a thick, cohesive paste. In custards and fillings, this thickening is what gives the mixture its body and smooth texture. When the liquid is heated with starch, the granules take in water, swell, and release starch molecules that mingle with the liquid to create a network that increases viscosity. This thickening happens at a temperature range specific to the starch being used, so the filling becomes firm enough to set as it cools. Eggs can also help set custards, but the initial thickening that provides the body comes from gelatinization. Other processes like proteins coagulating, fats melting, or gases expanding cause different textural changes and aren’t the gelatinization mechanism.