The formula of citrus espresso is espresso, espresso or espresso, which belongs to espresso type. Espresso refers to extracting a small amount of coffee from ground coffee powder in a short time with high-temperature hot water and high pressure, that is, water temperature of about 90 degrees and pressure of 10 Pa, and quickly extracting about 25 ml of espresso. The method of making coffee is to use extremely hot but not boiling hot water to brew at high pressure and grind it into very fine coffee powder to make coffee. It was invented and developed in Italy. It began in the early 20th century, but before the mid-1960s, it was only a beverage made by steam pressure. It was not until the invention of the spring lever coffee machine that espresso became a well-known beverage today. The pressure used in the production process is usually 9 to 10 atmospheric pressure or bar pressure.