Natural fermentation with delayed inoculation of the yeast Torulaspora delbrueckii: Impact on the chemical composition and sensory profile of natural coffee.

All coffee production stages occur in a microbiome, which is generally composed of bacteria, yeasts, and filamentous fungi. The use of starter cultures in post-harvest processing stages is an interesting alternative, since they promote faster removal of mucilage and incorporation of compounds that improve sensory quality, which can result in diverse sensory attributes for the beverage. This study was therefore developed with the objective of evaluating the effect of the following processing procedures on the chemical and sensory characteristics of the coffee beverage: first, fermentation of coffee fruit of the yellow Catucaí variety of Coffea arabica with indigenous microorganisms, followed by inoculation of the starter culture Torulaspora delbrueckii CCMA 0684 during the drying stage. The fruit was divided into two lots, which were differentiated by a natural fermentation process before drying began. The starter culture was inoculated on the coffee at different times during the drying process: at 0 h, 24 h, 48 h, or 72 h after drying began. The sensory attributes, the volatile compound composition of the roasted beans, the organic acid profile, the bioactive compounds, and the fatty acid profile of the green coffee beans were analyzed. The fatty acid and bioactive compound content showed little variation among treatments. Analysis of volatile compounds and organic acids and evaluation of sensory attributes made it possible to distinguish the two treatments. We conclude that natural fermentation of coffee fruit improve the chemical and sensory quality of the coffee beverage. The effect of natural fermentation may be before inoculation of the starter cultures or even during drying.

1H NMR spectroscopy applied to identify chemical aging markers in green coffee (Coffea arabica L.).

Nuclear magnetic resonance (NMR) was used to identify metabolic changes in green coffee beans stored in 3 different packages. Sensory and NMR analyses were performed at 0, 3, 6, 9, 12 and 18 months of storage. The decrease in the sensory quality of beverages by aging was more pronounced in the paper bags after 6 months of storage. High barrier bags and vacuum packs were able to maintain quality for 18 months of storage, regardless of the coffee processing method. The NMR technique allowed the differentiation of coffee packed in paper bags from the 3rd month of storage. These results indicate that it is possible to anticipate by up to 3 months the identification of changes that would otherwise only be noticed through sensory analysis after six months of storage. Choline and glycerophosphocholine are the main chemical compounds associated with the changes observed in the storage of green coffee in paper bags.

Impacts of quaker beans over sensory characteristics and volatile composition of specialty natural coffees.

The objective of this study was to evaluate the volatile composition and the sensory effect of the presence of Quaker beans in natural specialty coffee beverage and, consequently, to confront the requirement of the Specialty Coffee Association regarding the total absence of Quaker beans in a natural specialty coffee batch. Sensory analysis and volatile composition were performed for three different colorations of Quaker beans, added separately to natural specialty coffee samples at seven different concentrations. Beans with color equal to or above Agtron 82.8 negatively affected the sensory characteristics of natural specialty coffee only from the presence of 7 Quaker beans in one cup (65 beans). Through the analysis of volatile composition, volatile compounds formed during roasting were identified in Quaker beans from precursors present in raw immature beans. Therefore, the color and sensory characteristics of Quaker are a consequence of the chemical composition of an immature bean.

Raman spectroscopy for the differentiation of Arabic coffee genotypes.

The objective of this study was to evaluate the ability of Raman spectroscopy to identify the genotype of green coffee beans. Four genotypes of Arabic coffee: one Mundo Novo line (G1) and three Bourbon lines (G2, G3, and G4). The harvest was selected using a wet processing method. Raman spectra of the samples were obtained using a FT-Raman RFS/100 spectrometer in the spectral range of 3500-400 cm-1. The data were treated using chemometric unsupervised classification tools and supervised analysis. Using the unsupervised analysis (PCA), the apparent tendency of agglomeration between samples G1 and G3 was verified. These differences were present in the spectral bands that are characteristic of fatty acids and kahweol. Based on this information, a classification model to discriminate (PLS-DA) the Mundo Novo and Bourbon samples was utilized. Raman spectroscopy allowed the building of an adequate model to differentiate between coffee genotypes.