Enhancement of Arabica coffee quality with selected potential microbial starter culture under controlled fermentation in wet process

Coffee is a significant agricultural commodity that is well-known and enjoyed all over the world for its distinct flavor and aroma. The quality of coffee is affected by various parameters. The existing coffee processes, which rely on natural microorganisms, are uncontrollable, resulting in product inconsistency. To overcome this problem, this study aimed to investigate the potential use of selected microbial inoculants in wet method processing and the effects of fermentation time and temperature on coffee quality. Selected yeasts, bacteria, and lactic acid bacteria, isolated from the coffee fermentation process, were used as the starter cultures. Twenty-four conditions were set. At the 0 and 24 h of fermentation, total bacterial and yeast counts, as well as pH, were measured and trend to change during fermentation. After fermentation, coffee beans were subjected to sensory evaluation by Quality-Arabica Graders. Results showed that specific microbial starter culture under controlled conditions successfully improved coffee quality. Ten of the twenty-four types coffee beans tested were classified as specialty coffee with distinct cupping characteristics. Scaling up experiment was done by a mixture of three strains of Pichia kluyveri and Wickerhamomyces anomalus (condition Y4-04) at Doi Saket District, Chiang Mai, Thailand. According to the flavor profile derived from Q-graders, the cupping results was related to the volatile and water-soluble compounds identified by GC-MS and 1H NMR analyses. It suggests that the coffee quality can be improved by using starter cultures and carefully managing fermentation settings.