When beer is brewed in Asia, rice is traditionally used as an adjunct to provide additional sugars for the fermentation process. Under sufficiently high temperatures, the grain, which is primarily composed of starch, takes up water. The starch undergoes a gelatinization reaction when the moisture content is sufficiently high. Stirring and enzyme activity facilitate the removal of the outer gelatinized rice layers, and this starch dissolves into solution. The starch molecules are subsequently broken down by enzymes. The water uptake, gelatinization, and dissolution processes are modeled using a modified diffusion approach. The mass of starch molecules dissolved in solution as the cooking proceeds is determined. The dissolution process increases the speed of gelatinization, and the gelatinization front speed and the thickness of the gel layer are constant with time. The modeling takes into account different temperature regimes and a distribution of rice size. Such models help understand and optimize the total dissolved solids from this cooking process.