Evaluation of the Effect of Saccharomyces Cerevisiae on the Non-Volatile Compounds in Semi-Dry Coffee Beans Using Widely-Targeted Metabolomics Analysis

Abstract

Non-volatile flavor compounds directly determine the quality of coffee products, and the coffee fermentation process could significantly affect the flavor compounds. In this study, four single Saccharomyces cerevisiae [CMCC 1425 (HK), CMCC 1557 (JK), CMCC 1793 (GK), CMCC 32762 (ZK)], one mixed S. cerevisiae (MK), and natural fermentation (CK) were used to treated coffee berries, and the influences of the types of starter on non-volatile metabolites and coffee quality were assessed by sensory evaluation and widely-targeted metabolomics analysis. The correlation between the key differential metabolites and the sensory attributes was determined using the partial least squares regression (PLSR). The results indicated that S. cerevisiae led to a significant change in the color of the coffee and improved their aftertaste, overall, and balance. A total of 127 key differential non-volatile metabolites, including organic acids, phenolic acids, flavonoids and alkaloids etc., were identified of the GK, HK, JK, MK and ZK compared to the CK. Most of the evaluated flavonoids were decreased in GK and ZK, and the alkaloids and organic acids exhibited reduction in the HK, relative to CK. An increase in luteolin and manninotriose* was noted in all S. cerevisiae fermentation coffee samples and the increase was the most significant in the HK, although it was the only that caused a decrease in coumarin. The PLSR revealed that most of the differential metabolites were positively correlated to the sensory characteristics. These findings provided a theoretical basis for future studies on using various yeast strains to improve coffee flavor and quality.

Keywords: Coffee, Non-volatile compounds, Saccharomyces Cerevisiae, Widely targeted metabolomics