What differentiates an accurate dose from an underdose in espresso?

An accurate dose in espresso is primarily differentiated from an underdose by visual color and taste attributes. When the dose is correct, the resulting espresso will have a balanced flavor profile and an appealing crema, which is the golden, foamy layer on top of the shot. An accurate dose produces a full-bodied and rich flavor, with proper sweetness and acidity.

On the other hand, an underdose typically results in a weak and watery espresso, lacking depth and complexity. This under-extraction leads to less crema and a flat taste, causing the espresso to be unsatisfying. The visual characteristics, like the crema's richness and the overall color of the espresso shot, along with the taste profile, are direct indicators of whether an espresso shot has been dosed correctly.

Factors like the size of coffee beans, brewing time, and type of milk used do play roles in the brewing process, but they are not the primary indicators that distinguish an accurate dose from an underdose in espresso.