Pump pressure, measured in bars, is a crucial factor in espresso extraction. A common belief is that higher pressure, such as 20 bars, results in superior espresso. However, the relationship between pressure and quality is more nuanced. While sufficient pressure is necessary to force hot water through finely-ground coffee, excessive pressure can lead to over-extraction and a bitter, unpleasant taste. Nine bars is generally considered the ideal pressure for optimal extraction.
The focus on high pressure likely stems from marketing efforts emphasizing power and performance. Historically, lower-pressure machines struggled to achieve consistent results. Technological advancements have since enabled precise pressure regulation in modern espresso machines. Understanding the interplay between pressure, grind size, and brewing time is more important than simply aiming for the highest possible pressure. This knowledge empowers users to fine-tune their brewing process for the best flavor profile.
