Yeast Diversity and Physicochemical Characteristics Associated with Coffee Bean Fermentation from the Brazilian Cerrado Mineiro Region
2017
The aim of this study was to evaluate the yeast diversity and physicochemical characteristics of spontaneous coffee bean fermentation conducted in the coffee-producing region in Cerrado Mineiro, Brazil. During 48 h of fermentation, yeast population increased from 6.60 to 7.89 log CFU·g−1, with concomitant pulp sugar consumption and organic acids production (mainly lactic (3.35 g·L−1) and acetic (1.27 g·L−1) acids). According to ITS-rRNA gene sequencing, yeast population was mainly represented by Saccharomyces sp., followed by Torulaspora delbrueckii, Pichia kluyveri, Hanseniaspora uvarum, H. vineae and Meyerozyma caribbica. SPME-GC-MS analysis revealed a total of 25 volatile organic compounds with predominance of hydrocarbons (9 compounds) and higher alcohols (6 compounds). The resulting fermented, roasted coffee beans were analyzed by diverse chemical analysis methods, including Fourier Transform Infrared (FTIR) spectroscopy and mineral and thermogravimetric analysis. The thermal decomposition of the coffee beans occurred in four stages between 90 and 390 °C, with significant mass loss (68%) after the second stage at 190 °C. FTIR spectroscopy confirmed the presence of the main organic functions associated with coffee aroma, such as aromatic acids, ketones, aldehydes and aliphatic esters. The results presented in this study enrich our knowledge concerning yeast diversity and physicochemical characteristics associated with coffee bean fermentation, and can be used to promote a controlled on-farm processing.
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