Protein profile and volatile compound associated with fermented coffees with yeast co-inoculation

Abstract

This work aims to analyze the protein profile and volatile compounds of coffees fermented with the indigenous microbiota and with the co-inoculation of three yeasts (Saccharomyces cerevisiae, Torulaspora delbrueckii, and Candida parapsilosis). Two-dimensional gel electrophoresis (2D-PAGE), MALDI-ToF/ToF (MS/MS), and gas chromatography (GC-MS) were performed. A total of 72 "spots" were detected by 2D-PAGE. 16 spots were selected for identification by MALDI-ToF/ToF, and 12 were identified (11S protein, 13S globulin basic chain, 17.6 kDa class II heat shock protein (HSP17.6-CII), 18.0 kDa class I heat shock protein, Seed of Late Development Stage, Pru ar 1, and FAR-1 protein). 81 main volatile compounds were detected and classified into alcohols, acids, aldehydes, esters, hydrocarbons, pyrazines, furans, thiols, and pyridines/pyrrols. The difference between the identified volatile compounds and their concentrations was detected in the treatments with and without inoculation after drying. The compounds formed in green coffee during fermentation can participate in several reactions during roasting, presenting different sensory profiles and contributing to coffee quality.

Keywords: 2D-PAGE; Co-inoculation; Fermentation; Proteomics; Specialty coffee; Starter cultures.