How yeast has transformed the coffee market by creating new flavors and aromas through modern post-harvest fermentation systems.

Building on the success of traditional fermented foods, the coffee industry has experienced a surge in research on the use of yeast in coffee bean fermentation. As the coffee industry continually seeks innovative approaches, it becomes crucial to understand the nuances of yeast's impact on coffee quality. This review explores the transformative impact of yeast on coffee fermentation and product quality. By investigating traditional (wet and dry processing) and emerging techniques (carbonic maceration and induced fermentation), it aims to understand how yeast selection and fermentation methods affect coffee's flavor, aroma, and quality. Additionally, this review provides critical discussions on underexplored topics, such as optimal storage conditions and health properties of fermented coffee, as well as regulatory, safety, and environmental concerns, offering a complete view of yeast's role in enhancing coffee's market appeal and quality. Based on criteria such as pectinolytic activity, stress tolerance, and aroma production, Saccharomyces cerevisiae and Pichia fermentans are the most studied yeasts affecting coffee quality. Their impact on the chemical of coffee is evident through the accumulation of aroma-enhancing compounds, such as alcohols, aldehydes, organic acids, esters, ketones, and terpenoids. Recent protocols involving co-inoculation between distinct yeast groups and lactic acid bacteria have emerged, exhibiting metabolic synergism and producing coffees with heightened body perception, improved aroma, and enhanced acidity. However, ongoing research is needed to explore novel fermentation systems, storage methods, and sustainable yeast biomass disposal practices, ensuring a more efficient and sustainable future for the coffee market. • Yeast fermentation enhances coffee flavor by producing unique aroma compounds. • Saccharomyces and Pichia have a strong potential to diversify coffee sensory profile. • Co-inoculation with lactic acid bacteria enriches coffee's body, acidity, and aroma. • Yeast fermentation can reduce harmful compounds, boosting coffee's health benefits. • Further research is needed on yeast selection and the optimal storage of fermented beans. [ABSTRACT FROM AUTHOR]