When it comes to coffee bean processing, longer fermentation times can result in a better taste, unlike traditional wisdom. Lactic acid bacteria play an important and positive role in this process. Other microbial species may also play a role in this process, but more research is needed to better understand their role. Study published on February 1 t T. Applied and environmental microbiology.
"The coffee cup is a complex end product of the chain: agriculture, post-harvest processing, roasting and brewing," said Chief Researcher Luc De Vuyst, Ph.D., Professor of Industrial Microbiology. and Food Biotechnology, Vrije Universiteit Brussel, Brussels, Belgium. "There are a number of options after post-harvest treatment, with wet processing and dry processing most commonly used." Wet treatment, commonly used in Arabic and specialty coffee, is a step that involves fermentation.
"We conducted a research on an experimental farm in Ecuador using a multi-phase approach, including microbiological, metabolomics and sensory analysis," said Dr. De Vuyst.
Fermentation was particularly important. During the extended fermentation leuconostocs, a lactic acid bacterial genus used for fermentation of cabbage in acid cabbage and acid starter, decreased in favor of lactobacilli, said Dr. Lactic acid bacteria had already been before fermentation, and these acid tolerant lactobacilli increased in this process.
However, it is difficult to establish a causal relationship between microbial and bean volatile compounds – those compounds that contribute to the smell of coffee, as many of these compounds may be microbiological, endogenous, or chemical in their bean, "said Dr. De Vuyst.
"However, we have seen the impact of microbial communities, especially lactic acid bacteria," said Dr. De Vuyst. They created fruit notes and could have a "protective effect on the quality of coffee during fermentation because their fermentation mass is acidified, providing a stable microbial environment and thus preventing the growth of unwanted microorganisms that often cause taste," he said.
"In addition, coffee beans have accumulated fermentation-related metabolites that affect the quality of green coffee beans and, consequently, the sensory quality of the coffee they make," said Dr. De Vuyst.
Dr. De Vuyst emphasized that the influence of each stage of the process on the taste of coffee is largely unmarked. "We were aware of many different microorganisms during wet coffee fermentation – enterobacteria, lactic acid bacteria, yeasts, acetic acid bacteria, bacilli and filamentous fungi," said Dr. this process.
Work was a collaboration between Vrije Universiteit Brussel and Nestlé Research Center. "Nestlé was interested in the main aspects of coffee processing, especially in the post-harvest processing chain to correlate with the baking process and, of course, the quality of the final cups," said Dr. De Vuyst.