Identification of native yeasts in Geisha coffee (Coffea arabica) and their effect as starter culture on the sensory and chemical characteristics of washed coffee

Abstract

The special quality of Geisha coffee has led to research and improvement of its sensory attributes through fermentation. The aim of this study was to identify native yeasts in Geisha coffee, isolate them, and assess their potential to enhance sensory and chemical quality in assisted fermentation processes. The study was conducted in three phases: identification of yeast species (1); isolation and use in fermentation processes compared to commercial inoculum (2); and evaluation of the chemical composition and antioxidant capacity of the resulting coffee (3). Yeasts were identified through macro and microscopic observations, pH and Brix measurements, and two yeasts were selected for comparison with commercial yeast. Sensory evaluations and chemical analyses were also conducted. Thirteen yeast morphospecies were identified in Geisha coffe belonging to six genera (Pichia, Candida, Sporobolomyces, Hanseniaspora, Saccharomyces, and Rhodotorula), with the genus Pichia sp. being the most abundant. Subsequently, two native yeasts from Geisha coffee (Pichia and Saccharomyces) were selected for cultivation and inoculation in washed Geisha coffee, comparing them with a control inoculum (optimized strain of Saccharomyces cerevisiae). Sensory analysis revealed that all samples were considered specialty grade (>90 points), with the highest scores for the control inoculum and native inoculum 1. Some sensory attributes included citrusy and fruity notes. The Candida sp. was observed in the evaluated washed Geisha coffee despite not being inoculated. Finally, no differences were demonstrated in flavonoid content, total polyphenols, and antioxidant activity.