Abstract
We examined the antioxidant activity, total polyphenol content (TPC), total flavonoid content (TFC), total tannin content (TTC) and physical characteristics of green coffee beans fermented with selected yeasts. There was no significant (p > 0.05) interaction effect between yeast-fermented coffee extracts and duration of fermentation on antioxidant activity (oxygen radical absorbance capacity [ORAC] and superoxide dismutase-like [SOD-like] activity). However, the mean of the antioxidant activity (ORAC and SOD-like activity) significantly (p < 0.05) increased in the fermented coffee extracts compared to unfermented coffee. There were significant (p < 0.05) interaction effects between yeast-fermented coffee extracts and duration of fermentation (24 h and 48 h) on the TPC, TFC, TTC and pH of the fermented solution and on the colors of the ground-roasted coffee. The TPC showed a pattern of increase in samples Ferm-1 and Ferm-3 as fermentation time increased from 24 h to 48 h. However, a decreasing TPC trend was observed in Ferm-2 as the number of fermentation hours increased from 24 to 48. The fermented coffee beans had a significantly higher flavonoid content than the unfermented coffee beans, while fermentation significantly decreased the tannin content compared to that in unfermented coffee.
Highlights
Post-harvest coffee processing has a significant impact on coffee quality [1]
A pH reduction was observed in the control treatment; the rate of pH reduction was
A pH reduction was observed in the control treatment; the rate of pH reduction was less compared to that of the yeast-inoculated treatments
Summary
Fermentation is one of the most critical post-harvest processing steps during wet processing. As described by Sunarharum et al [2] coffee aroma is influenced by diverse factors from the farm to the cup Both dry- and wet-processed coffees have been analyzed for their sensory profiles and have been perceived as more aromatic with fruity with acidic characteristics and retained minor bitter, burnt and woody notes [3,4]. These variations in sensory attributes are most likely associated with the fermentation process. A few studies have examined the effects of solid-state fermentation of green coffee beans, using several indigenous filamentous fungi, on the aroma of coffee [7,8]
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