Effect of Pichia kudriavzevii addition on coffee fermentation during natural and washed process methods

Abstract

Fermentation is a metabolic process mediated by microorganisms that plays a critical role in coffee processing by promoting mucilage degradation and converting sugars such as glucose, fructose, and non-reducing sugars into simpler metabolites, including organic acids, alcohols, and esters, which contribute to the development of volatile compounds expressed during roasting, such as 2-methylpyrazine and furfurylthiol. In this research, the influence of Pichia kudriavzevii yeast on the fermentation of Castillo® variety under field environmental conditions (48.00, 72.00 h fermentation; 17.00°C-42.00°C drying temperature; 9.50-12.50% final moisture content) were evaluated. There were significant differences in the consumption of reducing sugars in relation to fermentation time (48.00 h and 72.00 h), processing type (Natural process, Washed process), and fermentation method (Spontaneous fermentation and Inoculated with P. kudriazevii yeast). During the SCA sensory evaluation, attributes such as chocolate and vanilla fragrances/aromas were characterized in the Traditional Washed process (Colombian traditional postharvest method consisting of sorting cherries, depulping, fermenting, washing and drying) with spontaneous fermentation. By contrast, washed inoculated treatment obtained fruity notes such as blueberries, oranges, pineapple, and strawberries. SCA evaluation for Natural process with spontaneous fermentation showed notes such as winey, chocolate, caramelized, while Natural inoculated treatment was characterized by black tea, brown sugar and blueberry. On the other hand, the processing type presented significant differences, demonstrating influence on the sensory quality of coffee, where the highest score obtained was 86.13, corresponding to the Natural control of 48.00 h.