Modulation of the volatile and non-volatile profiles of coffee fermented with Yarrowia lipolytica: II. Roasted coffee

- Volatile profiles of roasted coffee were modulated by Y. lipolytica fermentation.
- Effects of Y. lipolytica fermentation were most prominent at light roast level.
- Certain fermentation effects observed in green coffee were preserved after roasting.
- Total volatile phenol levels in light roasted coffee increased after fermentation.
- Y. lipolytica fermentation of green coffee bean can promote coffee aroma modulation.

The fermentation of green coffee beans by Yarrowia lipolytica led to significant changes in the volatile and non-volatile profiles of green coffees (Part I). Therefore, the objective of this continuation study was to evaluate the effects of fermentation after roasting by characterizing the volatile profiles of coffees at three different roast levels and non-volatile profiles of coffee where the effects of fermentation on volatiles were most prominent (light roast). Y. lipolytica fermentation led to significant changes in the volatile profiles of roasted coffees which arose from both the modification of aroma precursors and the retention of volatile profile changes observed in green fermented coffees. The levels of 4-vinylguaiacol and 4-vinylphenol were 1.2-fold and 1.6-fold higher in light roasted fermented coffees respectively and could be explained by the higher levels detected in green fermented coffees before roasting. The levels of γ-butyrolactone were 5 times higher in light roasted fermented coffees than unfermented coffees. The increase in sulfur compounds levels and decrease in ketones levels were attributed to changes in the concentrations of aroma precursors like sugars and amino acids. Thus, this study highlighted the potential of utilizing yeast fermentation of green coffee beans for coffee aroma modulation.