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Inoculation with selected Saccharomyces cerevisiae yeast in coffee fermentation : Pilot- and industrial-scale evaluations of the impact on the process and coffee quality

Berthiot L., Lahon M.C., Alter P., Bertrand B., Durand N., Boulanger R., Maraval I., Ortiz-Julien A., Sieczkowski N.. 2017. Turin : Universita Del Piemonte Orientale, 1 p.. International Conference on Cocoa Coffee and Tea 2017. 4, 2017-06-25/2017-06-28, Turin (Italie).

When Arabica coffee undergoes a wet process, the harvested cherries are depulped and the mucilage that is still surrounding the bean is removed by a step of biochemical reactions also called ¿fermentation¿. Previous studies showed the impact of the inoculation of selected Saccharomyces cerevisiae yeast on coffee cup quality and a yeast strain-dependent effect was put into evidence. The aim of the present study was to evaluate two specific strains on different raw materials at pilot-scale and realize a scale-up of the treatments under industrial conditions. Pilot-scale experiments evaluated the selected yeasts that were inoculated during a fermentation step lasting either 12 or 36h in comparison with the spontaneous fermentation. The trials were repeated at industrial scale in order to evaluate the yeast inoculation impact at larger-scale (100 kg to 1 ton batches of depulped cherries) including several factors such as the maceration duration, the raw-material quality and maturity and the production area. The effect on the biochemical composition as well as volatile organic compounds (VOCs) of coffee was measured. Sensory analysis (SCAA method) was performed in order to determine the impact of yeast inoculation on cup quality. Whereas yeast didn't impact the global biochemical composition of the green coffee, the results of the volatile compounds analysis on the pilot-scale trials evidenced a higher amount of esters on the green coffee proceeding from the inoculated pulped coffee; and the sensory analysis revealed a yeast positive impact on coffee overall quality in particular for one of the studied yeast strain. The results from industrial-scale trials confirm the good performance of the selected yeast and its contribution to coffee overall quality.

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