Characterization of active-aroma wheel in contemporary coffee processes via gas chromatography–olfactometry, and sensory perspective

Abstract

This research is to study the difference in chemical changes during fermentation, between the new fermentation processes. Aroma descriptors and sensorial assessments can be effectively used to tailor made fermentation processes. Coffee cherries (Coffea arabica L. var. Catimor) were treated with three different processes as followed: 1) Dry process (control), 2) Semi-carbonic maceration process (SCM): Carbon dioxide gas was injected to replace oxygen, and 3) Yeast process: coffee cherries were fermented by commercial yeast strain Saccharomyces cerevisiae var cerevisiae. SCM and Yeast processes were both incubated at 17±1oC until mucilage of pulped coffee and pectin layer reached to 4.2-4.3 of pH value. Low air temperatures (20-33 oC), low relative humidity (25-60%) to dry coffee samples to the desired 12.5% moisture content was used. The chemical component of the intact mucilage during fermentation was analyzed. The active-aroma attributes of roasted coffee were qualified and intensified by gas chromatography–olfactometry, categorized as followed: Enzymatic, Sugar browning, Dry distillation and Aromatic, and translated into an active-aroma wheel. The quality cup scores were evaluated by certified Q arabica graders, according to the standard of the Specialty Coffee Association. Results shows that, when compared to Control, SCM and Yeast process had a greater potential when it comes to increasing active-aroma attributes (twenty, twenty-nine, and twenty-two active-aroma attributes respectively). The fermentation process of SCM and Yeast process changes the post fermentation chemical composition of coffee cherry, a decrease in pH value, and an increase in acidity and ethanol. Both processes resulted in an improvement in aromatic attributes of roasted coffee, in both types and intensities. In line with the cup quality’s final scores of 81.50, and 82.83 (specialty coffee), respectively, both processes scored higher than the Dry process (79.42 cup score), with coffee from Yeast process scoring the highest in significant difference.