Why are dark roasts considered more soluble?

Dark roasts are considered more soluble primarily due to the larger internal channels that form during the roasting process. As coffee beans roast, they undergo significant physical changes, including expansion and the creation of gas-filled channels within the bean structure. This increased channel size allows water to penetrate the beans more easily during brewing.

The larger internal pores facilitate more effective extraction of soluble compounds, such as oils and sugars, resulting in a quicker dissolution into the brewing water. This contrasts with lighter roasts, which typically retain more of their cellular structure and thus have smaller channels that can hinder water flow and extraction efficiency. Therefore, the physical transformation of the bean during the roasting process significantly contributes to the solubility of dark roasts.