Behavior of yeast inoculated during semi-dry coffee fermentation and the effect on chemical and sensorial properties of the final beverage

Abstract

Pulped Mundo Novo and Ouro Amarelo coffee beans were inoculated with Saccharomyces cerevisiae (CCMA 0200 and CCMA 0543) during semi-dry coffee fermentation and compared with a non-inoculated control. Samples were collected throughout the fermentation process (12days) to evaluate the persistence of the inoculum by Real-Time quantitative PCR (qPCR). Also, the chemical composition of the beans was determined by HPLC and GC-MS and the roasted beans were sensorial evaluated using the cupping test. S. cerevisiae CCMA 0543 had an average population of 5.6logcell/g (Ouro Amarelo cultivar) and 5.5logcell/g (Mundo Novo cultivar). Citric, malic, succinic and acetic acid were found in all samples, along with sucrose, fructose, and glucose. There were 104 volatile compounds detected: 49 and 55 in green and roasted coffee, respectively. All coffee samples scored over 80 points in the cupping test, indicating they were specialty-grade. Inoculation with the CCMA 0543 strain performed better than the CCMA 0200 strain. This is the first time that qPCR has been used to assess the persistence of the inoculated strains populations during coffee processing. Strain CCMA 0543 was the most suitable as an inoculant due to its enhanced persistence during the process and number of volatile compounds produced.

Production of coffee (Coffea arabica) inoculated with yeasts: impact on quality

“…Mundo Novo was characterized by caramel, herbaceous, brown sugar, and honey flavors and aromas. Other studies also showed that the starter yeast promoted coffee quality and that the same strains started to behave differently according to the coffee variety due to different sugar concentrations found in the coffee varieties …”

“…The following samples were analyzed: pulped coffee at the start of fermentation, coffee without mucilage (demucilated coffee) at the end of fermentation, and dried coffee at the final drying time. Samples were prepared according to Ribeiro et al 6 The extracts were analyzed using a high-performance liquid chromatography system (Shimadzu, Japan). A Shimpack SCR-101H (7.9 mm × 30 cm) column was used with a 100 mM solution of perchloric acid with a flow rate of 0.6 mL min −1 as the mobile phase.…”

“…Recently, researchers showed that coffee fermentation inoculated with specific microorganisms processed by dry and semidry methods increased the production of volatile compounds and consequently improved the flavor and aroma of the beverage . However, little is known about wet processing.…”

“…The beans are removed from the tanks and sun dried. 6 The microorganisms involved during wet processing have been described and are known to belong to bacterial and yeast groups. 2,[7][8][9] However, the use of starter cultures in this form of processing is unknown.…”

“…2,3 Recently, researchers showed that coffee fermentation inoculated with specific microorganisms processed by dry and semidry methods increased the production of volatile compounds and consequently improved the flavor and aroma of the beverage. 6,11,14,15 However, little is known about wet processing. Wet processing removes approximately 60% of the cherry volume, significantly reducing the time (from 3-5 weeks to 8-10 days) and area required for drying the beans in relation to dry processing.…”