Quality “In Cup” of Espresso Coffee: Data from over Ten Years of Investigation

In this work the results of a wide research concerning the “Quality in cup” of espresso coffee directly prepared in coffee shops (688) of six different geographic area of Italy (Central and Northern) performed during a period of over 10 years were discussed. In this way different process variables such as type of roasting plant, type of grinding-batcher plant, type of extraction machine (manual, automatic, semi-automatic), blend, water temperature and pressure, weight of powder and its compression inside the filter, were analysed before coffee extraction. Furthermore, the quality in cup was evaluated by measuring the most important indexes such as the consistency and the height of cream, pH, °Bx and volume of brew. Several experiment were performed in laboratory scale with the aim to evaluate the effects of possible uncontrolled variables during the coffee brew preparation in coffee shops. Over than 9000 data were then statistically elaborated by Anova analysis, Mann-Whitney test and Levene test. The Principal component analysis (PCA) of extraction process data and of quality parameters of espresso coffee was used in order to discriminate the quality characteristics of coffee brews in relation to the different geographic areas and to discriminate the significant differences among the years of the investigation (from 2000 to 2011). From results, the type of extraction plant and of grinding-batcher plant as well as a good training of bar operators emerged as the most affecting variables the quality of espresso coffee.