Fermentação anaeróbica autoinduzida (SIAF) com e sem inoculação de leveduras: viabilidade da semente, composição química e qualidade sensorial do café

Abstract

Coffee fermentation occurs due to the production of metabolites produced by epiphytic microorganisms present in the fruit itself and transferred to the interior of the grain. In addition, during fermentation, germination metabolic processes are initiated within the seed, affecting the embryo's viability, the chemical composition, and the sensory quality of the coffee. In this context, our objective was to evaluate the effects of coffee fermentation on seed viability and sensory quality of the beverage using yeast as starter cultures (Saccharomyces cerevisiae CCMA 0543, Candida parapsilosis CCMA 0544 and Torulospora delbrueckii CCMA 0684), by induced anaerobic fermentation (SIAF) in Coffea arabica L. Variety Yellow Topaz, by natural and pulped processing. Yeast monitoring was performed by real-time polymerase chain reaction (qPCR), analysis of organic acids (citric, malic, succinic, and lactic) and sugars (sucrose, glucose, and fructose) by high-performance liquid chromatography (HPLC). Volatile compounds by gas chromatography-mass spectrometry (GC-MS). Seed viability and damage were monitored by tetrazolium test, electrical conductivity, seed germination test, and enzymatic analysis by gel electrophoresis (catalase, alcohol dehydrogenase, esterase, and isocitrate lyase). Yeasts S. cerevisiae and T. delbrueckii showed the highest populations during fermentation compared with the control SIAF treatment and the conventional process without inoculation. A decrease in the concentration of sugars (sucrose, glucose, and fructose) and acids (citric, malic, and succinic) was observed. Treatments processed by SIAF showed lactic acid production during the end of fermentation (the control treatment SIAF showed the highest production with 8.33 g/kg in pulped coffee and 3.95 g/kg in natural coffee). Key enzymes of the metabolic processes of germination (isocitrate lyase and e endo-β-mannanase) demonstrated the beginning of germination during coffee fermentation, as well as processes of defense against oxidative (esterase and catalase) and environmental stress (anaerobiosis determined by alcohol dehydrogenase). Changes in seed physiological quality were identified, including decreased embryonic viability by tetrazolium test (the treatment inoculated with S. cerevisiae was the treatment with the lowest % embryonic viability, with 52.5 in natural coffee and 60.0 in pulped coffee). The conventional treatment processed by natural coffee did not show a decrease in the % of seed germination. All coffees obtained scores greater than 80 points. The coffees with the highest sensory score were obtained from inoculated and fermented by SIAF; yeast T. delbrueckii (86.50) in pulped coffee and yeast C. parapsilosis (85.90) in natural coffee. Coffees fermented by SIAF were characterized by aromas and flavors of citrus, caramel, honey, chocolate, and chestnut. The coffee fermentation process by SIAF with yeast inoculation affected the viability of the coffee bean but not the sensory quality of the drink, indicating that the use of yeast starters by the SIAF method favors the production of special coffees with differentiated sensory characteristics.