Differences in volatile compounds and antioxidant activity of ripe and unripe green coffee beans (Coffea arabica L. 'Catimor')
Aroma characteristics and antioxidant activity are main quality markers for a good cup of coffee. These attributes are influenced by the degree of ripeness of the coffee berries. Therefore, the aim of this study was to study the differences between ripe and unripe green coffee beans in volatile compounds and antioxidant activities to evaluate the selection process of coffee berries. Two types of green coffee beans processed from ripe and unripe coffee berries from the same plantation were characterized for their volatile components by solid-phase micro-extraction gas chromatography/mass spectrometry (SPME-GC/MS) using 2-methyl-3-heptanone as an internal standard. More than 200 peaks of volatile constituents were found in both unripe and ripe green coffee. Alcohols and ketones were the most abundant groups of volatile compounds in unripe green coffee, while the concentrations of these two groups decreased during the ripening process. In contrast, aldehydes, acids, and esters increased. Various compounds were found only in ripe green coffee, such as 1‑hexanol, 2-heptanol, 2-ethyl-1-hexanol, 2,2-dimethyl-3-4-pentadienal, methyl hexanoate, methyl phenylacetate, methyl salicylate, methyl-(2E)-2-methyl-2-butenoate, and 2,7-dimethyl-oxepine. In terms of antioxidant activity measurements, total phenolic content of ripe and unripe green coffee beans was 59.94±4.14 and 54.56±0.73 mg gallic acid equivalents (GAE) g-1 coffee beans; diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (%) was 71.74±5.26 and 70.68±4.78, and reducing antioxidant power by ferric-reducing antioxidant potential (FRAP) assay was 66.98±4.70 and 52.72±3.20 mg Trolox g-1 coffee beans, respectively. These results can be used as information for correct selection of coffee berries prior to other stages of coffee processing.
Kulapichitr, F., Borompichaichartkul, C., Pratontep, S., Lopetcharat, K., Boonbumrung, S. and Suppavorasatit, I. (2017). Differences in volatile compounds and antioxidant activity of ripe and unripe green coffee beans (Coffea arabica L. 'Catimor'). Acta Hortic. 1179, 261-268
green coffee, coffee ripeness, SPME-GC/MS, antioxidant, postharvest process