Modulation of the volatile and non-volatile profiles of coffee fermented with Yarrowia lipolytica: I. Green coffee

Yeast starter cultures have been used in the fermentation of different coffee substrates to modulate the volatile and aroma profiles of coffees with the exception of green coffee beans. This two-part study aimed to modulate the volatile profiles of roasted coffee via the fermentation of green coffee beans with a non conventional aerobic yeast Yarrowia lipolytica. The objective of part I of this study was to evaluate the effects of Y. lipolytica fermentation on the volatile and non-volatile profiles of green coffee beans. After fermentation, sugars concentration decreased by 1.2-fold while the amino and phenolic acids concentrations decreased by 1.3-fold. The decrease in phenolic acid concentration could account for the 1.5-fold increase in the volatile phenols levels resulting from phenolic acid catabolism. The degradation of L-phenylalanine via the Ehrlich pathway by the yeast led to a 1.9-fold increase in 2-phenylethanol levels, whereas the decreases in alkanes, acids and aldehydes levels were attributed to the hydrophobic substrate metabolizing pathways that were unique to Y. lipolytica. Hence, this work showed that Y. lipolytica fermentation of green coffee beans resulted in the modification of the aroma precursors and volatile composition of green coffees. (C) 2016 Elsevier Ltd. All rights reserved.