Abstract

Background: The coffee drinking habits strongly vary as effect of several points, such as culture, lifestyle, social behavior, preferences, and economic aspects. However, it has been widely recognized that regularly drinking two or three coffees per day provides several health benefits. Nevertheless, the total intake in healthy compounds is largely affected by several variables among which the roasting, the grinding and the brewing method are the most important. On these pillars we have analyzed the effect of roasting, grinding and three brewing methods on the content in phenols, caffeine and antioxidants of coffee samples.
Methods: Three roasting degrees (light, medium and dark) and three grinding levels (fine, fine-coarse and coarse) were used to prepare Espresso, American and Turkish coffee samples for a total of 27 experimental conditions. Physical and chemical analyses as well as caffeine content, polyphenols and antioxidant activity were analyzed for each experimental condition.
Results: As effect of roasting, the antioxidant activity of coffee brew increased due to melanoidins produced at high temperature while the ‘native’ polyphenols of the green beans were significantly lost during roasting. Grinding level affected the kinetic extraction more than pressure, dose and particle size although a significant variation was always observed. As consequence regular espresso of 25 mL may contain from 80 to 120 mg of caffeine depending of the variance in grinding process. Overall, a regular cup (200 mL) of American coffee resulted to contain average values of 280-350 mg of caffeine, 500-1200 mg of gallic acid and 500-1200 mg trolox.
Conclusion: American coffee was the richest in caffeine, polyphenols and antioxidant activity when considering a regular coffee commonly consumed at bar. A more precise standardization of the grinding, when consuming coffee at bar, is one of the most important future step to tackle the wide variability in quality estimated among repeated coffees.