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Metabolomic Profiling of Cultured-Yeast and Spontaneously Fermented Coffees
* 1 , 2 , 3 , 1
1  Hochschule Mannheim, Paul-Wittsack-Straße 10, 68163 Mannheim, Germany
2  Coffee Consulate, Hans-Thoma-Strasse 20, 68163 Mannheim, Germany
3  TU Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany
Academic Editor: Dirk W. Lachenmeier

https://doi.org/10.3390/ICC2024-18020 (registering DOI)
Abstract:

Coffea arabica and C. canephora with all varieties make up for the largest share of cultivated coffee worldwide, whereas the C. liberica species only represents a minor proportion. This is mainly because the taste profiles of C. canephora and C. liberica varieties are typically less popular than those of C. arabica coffees. However, with evolving coffee fermentation methods, the sensory profiles of the three coffee species advance into more complex profiles with less off-flavors and as such, alter this traditional distribution. Pure culture yeasts partially suppress the growth of unwanted microorganisms and alter the composition of organic precursor compounds, which ultimately leads to better, more favorable sensory profiles of the roasted coffee. This substantially boosts the quality of so far less popular Coffea species. Our study describes a cross-platform metabolomic approach for the evaluation of the changes of the sensory metabolome of green and roast coffees. The approach is designed in a comprehensive manner for the volatile fraction (“volatilome”) and the soluble fraction (classical metabolome). For the analysis of the volatilome, GC-MS, as well as GC-IMS was utilized. The non-volatile compounds were analyzed and tentatively identified with LC-HRMS, paired with metabolomic tools. First results of the volatilomics platform showed a substantial difference in the volatile organic compounds (VOCs) profile of controlled fermented and wild fermented coffees. Preliminary orthogonal analyses based on non-targeted HPLC-ESI-HRMS tentatively allowed for the identification of individual substance groups that showed process-specific formation or breakdown during controlled coffee fermentation. The data of all platforms was evaluated and compared. Through this, a holistic and complementary view of the volatile and non-volatile metabolome of cultured-yeast and spontaneously fermented coffees was accomplished. This talk presents a direct comparison of the metabolomic analysis of different types of fermentation approaches of coffees, as well as first results of the metabolomic platform will be shown. An outlook to the future and the relevance of fermentation for flavor enhancement of coffee will be given.

Keywords: metabolomics; volatilomics; metabolomic profiling; coffee fermentation
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