What indicates that an espresso shot has been left to sit too long?

The indication that an espresso shot has been left to sit too long is the change in flavor to bitter and burnt. When an espresso shot is freshly brewed, it has a balanced flavor profile with a rich, complex taste that includes sweetness and acidity. However, as the espresso sits, chemical reactions continue to occur, often resulting in the extraction of undesirable compounds.

This process of over-extraction leads to a bitter and charred taste, as the heat and exposure to air significantly alter the composition of the coffee. The crema, which is the golden-brown frothy layer on top of the espresso, also begins to deteriorate in quality, contributing to the overall decline in flavor. Recognizing these changes is important for baristas and coffee enthusiasts who aim to serve the best-tasting espresso.

While the other options present certain conditions of espresso, they do not signify the negative effects of allowing a shot to sit too long as clearly as the degradation of flavor does. For instance, if an espresso shot is too hot to touch, it may indicate that it was brewed at a high temperature rather than sitting too long. An overly thick crema or a perfectly creamy appearance does not directly correlate with time spent sitting; those aspects could be influenced by brewing techniques or the