The researchers studied different types of rice to see how the activity of certain enzymes during grain filling affects the quality of the rice when cooked. They found that the timing and level of enzyme activity, especially for starch branching enzyme, influenced the taste and texture of the rice. High-quality rice had higher enzyme activity later in the grain filling process, while low-quality rice had higher activity earlier. This suggests that using rice with specific enzyme activity levels at different stages of grain filling could help improve the overall quality of japonica rice for eating and cooking.