Which of the following affects the brewing process in coffee?

The quality of water used in the brewing process is indeed a critical factor that can significantly influence the overall flavor and extraction of coffee. Water makes up about 98% of brewed coffee, which means its mineral content, pH balance, and presence of impurities can directly affect the taste and quality of the final beverage. High-quality water will ideally have a balanced mineral content that enhances extraction while avoiding any unpleasant flavors or odors that might unintentionally come from poor-quality water.

In terms of other options, while the size of the coffee mug or the material of the cup can impact the thermal dynamics and presentation, they do not fundamentally alter the brewing process itself. Similarly, the color of the coffee beans typically pertains more to the roast level and does not directly influence the brewing process as much as the water quality does. Therefore, focusing on the quality of water used is essential for achieving optimal coffee extraction and flavor.