Microbiological and Chemical Characteristics of Wet Coffee Fermentation Inoculated With Hansinaspora uvarum and Pichia kudriavzevii and Their Impact on Coffee Sensory Quality

Hansinaspora uvarum and Pichia kudriavzevii were used as starter cultures to conduct inoculated wet fermentations of coffee beans, and their growth, metabolic activities and impact on the flavor, aroma and overall sensory quality of coffee were compared with spontaneous fermentation (control). H. uvarum and P. kudriavzevii dominated the fermentations, growing to maximum populations of about 10.0 log CFU/ml compared with 8.0 log CFU/ml in the spontaneous fermentation. The dominance of the inoculated yeasts led to faster and more complete utilization of sugars in the mucilage, with resultant production of 2–3 fold higher concentrations of metabolites such as glycerol, alcohols, aldehydes, esters, and organic acids in the fermented green beans. Cup tests showed coffee produced from the inoculated fermentations, especially with P. kudriavzevii, received higher scores for flavor, aroma and acidity than the control. The findings of this study confirmed the crucial role of yeasts in the wet fermentation of coffee beans and their contribution to high quality coffee, and demonstrated the potential H. uvarum and P. kudriavzevii as starter cultures in the process

The role of wet fermentation in enhancing coffee flavor, aroma and sensory quality

This study investigates the impact of wet fermentation on flavor volatiles and sensory quality of coffee beans and beverage. Pulped coffee beans were kept underwater for 36 h before air-drying and roasting, and volatiles in the beans were characterized by solid-phase microextraction and gas chromatography–mass spectrometry. A total of 79 volatiles were identified. Fermented roasted beans had higher concentrations of ethanol, isoamyl alcohol, 3-methylbutanal, benzaldehyde, acetaldehyde, and ethyl acetate compared with mechanically processed (no fermentation) beans; whereas, ketones, pyrazines, pyrroles, pyridines, furans and sulfides were not significantly different between the two treatments. Coffee made with fermented beans was rated significantly higher in flavor, aroma, acidity, body and uniformity scores with noted fruity aroma compared with beverage made with mechanically processed beans in sensory evaluation (cup test) by a 3 Q-Grade Coffee Certification Panel. The findings demonstrated wet fermentation played an important role in coffee flavor, aroma and sensory quality