What is the purpose of the pressure gauge on an espresso machine?

The purpose of the pressure gauge on an espresso machine is to measure the pressure during espresso extraction. This measurement is crucial because the extraction process for espresso relies on water being forced through finely-ground coffee under specific pressure conditions, typically around 9 bars (or 130 psi) for optimal results. Monitoring this pressure allows baristas to determine whether the espresso is being extracted correctly. If the pressure is too low, it may result in under-extraction, leading to a weak flavor; if it is too high, over-extraction can occur, resulting in a bitter taste. Therefore, the pressure gauge is essential for maintaining the quality and consistency of espresso drinks.

The other choices do not relate directly to the functionality of the pressure gauge. The temperature of water is important for brewing, but it is usually measured with a thermometer rather than a pressure gauge. The amount of coffee grounds can be assessed through weight measurements rather than pressure readings, and total brewing time is tracked using timers, not gauges that measure pressure.