Gelatinization (Koka)

Koka (gelatinization) refers to the physical change that occurs when water is added to starch-containing ingredients such as rice and they are heated. In this process, starch granules absorb water and swell, turning into a transparent, sticky, paste-like substance. Because gelatinized starch is broken down more readily by enzymes, it is an important step in the fermentation process. In sake brewing, gelatinizing the rice after steaming allows the later enzymatic saccharification (conversion of starch into sugar) to proceed smoothly, leading to alcohol fermentation. Gelatinization is an important factor that directly affects the flavor and aroma of sake.