Processing of the coffee bean at the origin is increasingly becoming a major tool for specialty coffee producers around the world to differentiate the flavor of coffee beans. The processing method of coffee after harvest influences the final flavor and proceeds predominantly though either a wet (washed) or dry (natural) process. The natural process consists of drying the whole coffee fruit prior to removing the pulp.<br/><br/>To understand the flavor of Arabica natural coffee, in particular the ‘fruity’ or ‘winey’ character (sometimes called ‘Mocha’), three studies were designed. These investigated: 1. the sensory character of washed and natural coffee from 22 farms in Guerrero, Mexico using fast sensory profiling (FSP); 2. flavor of natural and washed coffees from seven countries using FSP, volatile organic compounds (VOCs) of green beans using proton transfer reaction mass spectrometry (PTR-MS) and VOCs of roasted beans using gas chromatography mass spectrometry/olfactometry (GC-MS/O); and 3. manipulation of the coffee cherries drying rates to modify microbial growth and achieve different flavor characters, assessed as above.<br/><br/>FSP of natural coffees from Mexico were characterized as tropical, red fruit, dried fruit and fermented, whereas washed coffees were described as floral, spicy and nutty. Geography (including country-specific processing factors) dominated the flavor of the coffee from study 2, though the mocha character of a naturals sub-group was linked to the presence of ethyl 2-methyl-butanoate and ethyl 3-methyl-butanoate. Varying the drying conditions modified the flavor of the resulting coffee and modified the ethanol: methanol ratio, indicating that the microbial composition was altered by drying conditions. Fermentation for two days prior to drying, favored the production of red fruit and fermentation flavors, and induced correspondingly higher abundances of ethyl 2-methyl-butanoate and 3-methyl-butanoate. Fermentation during post-harvest processing appears to create compounds that can be carried over through roasting and directly impact the cup.

Investigating the flavor of natural (dry process) coffee

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