Impacto da fermentação e da secagem na qualidade dos grãos de café ao longo de 18 meses de armazenamento

Abstract

Emerging processing methods have been employed to enhance the sensory quality of coffee, with fermentation being one of the most widely used techniques. During fermentation, the conversion of pulp constituents into active flavor components, such as volatile compounds and organic acids, occurs, influencing sensory quality and producing distinct and exotic coffees. It has been established that the improvement in sensory quality of fermented coffee depends on factors such as predominant microbiota, coffee variety, and processing method. However, after fermentation, coffee beans must undergo drying and storage, and studies on coffee fermentation do not describe the effect of drying methods on the shelf life of fermented coffees. During the drying stage, physical and biochemical changes take place in the beans, and intermittency is one of the technologies used to preserve the cellular membrane system, chemical quality, and sensory attributes of the beans. Even after drying, the beans remain metabolically active. However, the dynamic transformations occurring in the beans during storage are complex and can be intensified depending on the processing and drying methods. Therefore, intermittent drying and the use of inoculation for fermentation are believed to extend the shelf life of coffee. This study was divided into two articles with the aim of understanding the effect of inoculation, fermentation time, and drying method on the shelf life of coffee during storage, employing (i) Gas Chromatography for the determination of volatile compounds and fatty acids, and Check All That Apply sensory analysis; (ii) High-Performance Liquid Chromatography for the determination of sugar profiles, organic acids, and bioactive compounds, and sensory analysis using an intensity scale. Ripe Arabica coffee fruits were used for the fermentation of natural coffees in hermetic cylindrical containers. The fruits were divided into two batches, one for fermentation without inoculation (indigenous microbiota) and the other inoculated with the yeast Saccharomyces cerevisiae ADY B0620 for fermentation. Both batches underwent three fermentation periods: 0, 48, and 96 hours. Subsequently, the fruits were dried continuously and intermittently in mechanical dryers at an air temperature of 39±1 °C until the estimated water content reached 11% (w.b.). Once dried, the coffee in parchment was packaged in permeable bags and stored at room temperature for 30 days. The parchment coffee was then processed, and the beans were packed in high-barrier packaging for the storage experiment. The coffee beans were stored in a commercial warehouse in southern Minas Gerais, and samples were taken at 0, 6, 9, 12, and 18 months for the analysis of the chemical and sensory quality of the beans. The results indicate that volatile compounds such as furfuryl formate; 2-furanmethanol, acetate; 2-furancarboxaldehyde, 5-methyl-; 2-furanmethanol; fatty acids such as palmitic, stearic, and linoleic; sugars like glucose and fructose; and organic acids such as citric, malic, and quinic acids undergo changes during storage, depending on the presence of the yeast S. cerevisiae ADY B0620 in fermentation. Inoculation with S. cerevisiae ADY B0620 preserved the composition of fatty acids, volatile compounds, and organic acids during storage. Coffees fermented for 96 hours, regardless of inoculation, exhibited a longer shelf life than coffees with 0-hour fermentation, preserving their sensory quality for 18 months.