Effect of Bacterial and Yeast Starters on the Formation of Volatile and Organic Acid Compounds in Coffee Beans and Selection of Flavors Markers Precursors During Wet Fermentation

Abstract

Coffee quality has recently become a high demand of coffee consumers, due to all the specialty coffees available on the market. Specialty coffees can be generated by favoring growth of some groups of microorganisms during fermentation or by using starters. Just as yeast, a variety of bacteria can be used to generate important flavor precursors. The aim of this work was to test the efficiency of coffee sterilization and adhesion of microbial cells on beans, to evaluate the effect of yeast and bacterial starters on the production of organic and volatile compounds, and selection of potential flavor marker precursors during the wet fermentation. Three yeast and six bacterial starters were inoculated in coffee beans. Coffee sterilization and microbial adhesion was observed by scanning electron microscopy (SEM). Organic compounds were detected by high performance liquid chromatography (HPLC) and volatile compounds by gas chromatography–mass spectrometry (GC–MS). Micrographs from the SEM showed that sterilization was efficient, because there were no microbial cells after autoclaving for 5 min. Also, it was observed an increase of microbial cells from 0 to 48 h of fermentation. Malic, lactic, and acetic acid were only detected in the bacterial treatments. Volatile compounds: 4-ethenyl-1,2-dimethoxybenzene, heptadecanol, 4-hydroxy-2-methylacetophenone, and 1-butanol,2-methyl were only found in yeast treatments. Guaiacol was only produced by the inoculated B. subtilis starters. In conclusion, yeast starters were better producers of volatile alcohols and bacterial starters of acid compounds. This study allowed the selection of potential flavor marker precursors, such as heptadecanol, 4-hydroxy-2-methylacetophenone, 7-methyl-4-octanol, and guaiacol.

Review on factors affecting coffee volatiles: from seed to cup

“…From choosing the right starter culture 55 to the right fermentation container, 56 the purpose is to improve the flavor and aroma of the coffee, shorten the processing time and drying time, and increase the economic value of the product. Much data are available in the literature about the effects of this method on VOCs and the final quality of the coffee 57‐60 . Rosane Freitas Schwan's team has been studying the impact of fermentation on coffee quality for many years.…”

“…Much data are available in the literature about the effects of this method on VOCs and the final quality of the coffee. [57][58][59][60] Rosane Freitas Schwan's team has been studying the impact of fermentation on coffee quality for many years. Their latest report about coffee VOCs evaluated the effect of Saccharomyces cerevisiae (CCMA 0543) and Torulaspora delbrueckii (CCMA 0684) inoculation on the quality of three varieties of natural and pulped natural processed beans in the five largest arabica coffee-producing regions with different climate profiles.…”

The Altitude of Coffee Cultivation Causes Shifts in the Microbial Community Assembly and Biochemical Compounds in Natural Induced Anaerobic Fermentations

“…According to Martinez et al (2019) , bacteria are the primary acid producers in wet fermentation. Therefore, in this work, the bacterial community from dry-processed coffees was correlated with acids.…”

Dört Farkli Potansi̇yel Probi̇yoti̇k Kültür Kullanilarak Üreti̇len Türk Ti̇pi̇ Sarimsak Turşularinin Bazi Özelli̇kleri̇

“…It was thought that succinic acid might have been produced by yeasts as well as LAB, affected by changes in temperature and pH. Similarly, studies have shown that both yeasts and LAB produce succinic acid (Martinez et al, 2019). The presence of tartaric acid in all groups, albeit in low amounts, suggested the possibility of its natural presence.…”