Investigation of the factors that affect the volume and stability of espresso crema

Abstract

This study investigated the effects of key brewing parameters (basket size, particle size, temperature, brewing ratio, coffee freshness, bean variety, and degree of roast) on the crema volume and stability of espresso coffees. Moreover, the brewing time and pressure, as well as brew total solid and extraction yield were characterized. The results show that the crema volume was mainly affected by the coffee variety and freshness. A larger crema volume was generated from Robusta than Arabica beans. Moreover, the fresher the coffee, the greater the crema volume. Crema stability was strongly affected by basket size, with double- and triple-shot baskets producing more stable crema than that from the single-shot basket. Arabica beans resulted in brews with a more stable crema than Robusta, attributable to the higher lipids content in the former. In comparison, crema volume and stability were less affected by the particle size, brewing ratio, and brewing temperature. Besides elucidating the parameters that affect the crema volume and stability of espresso coffee, findings from this study are expected to be useful for café barista and coffee connoisseurs in preparing espresso coffee with consistent crema quality.

Keywords: Coffee brewing; Crema; Espresso; Extraction.