Identificação da mudança no perfil químico do Coffea arabica

Abstract

The sensory quality of coffee is largely influenced by intrinsic factors, such as species, genetics, and maturation stage, as well as extrinsic factors, including edaphoclimatic conditions and post-harvest processing methods. Climatic variations throughout the physiological cycle, such as temperature, solar radiation, and precipitation, can significantly impact the chemical composition and, consequently, the sensory profile of coffee. Non-volatile compounds, essential for primary and secondary metabolism, are directly linked to the formation of volatile compounds responsible for the beverage’s aroma and flavor. In this study, chemical and sensory variations were investigated over two years (2020 and 2021) using analytical techniques such as mid-infrared (MIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). Additionally, five post-harvest processing methods were evaluated to understand how these factors interact under different climatic conditions. GC-MS results revealed effective discrimination between harvest periods. In September, a higher abundance of acids, sulfur compounds, alcohols, aldehydes, thiazoles, esters, pyrazines, diacetones, and pyrans was observed. In contrast, coffees harvested in November showed a higher concentration of furans, thiophenes, thiols, pyrroles, and phenols. MIR analysis revealed low chemical separation between harvests within the same year (2021). However, certain spectral regions, such as 3200 cm−1, associated with intermolecular hydrogen bonding interactions, and the 1455 cm−1 range, previously linked to functional group vibrations in lipids, caffeine, and chlorogenic acids, were crucial in identifying separation trends between harvests. On the other hand, sensory evaluation showed more pronounced differences, particularly in coffees subjected to induced fermentations. Partial Least Squares Discriminant Analysis (PLS-DA) demonstrated high efficiency in classifying samples, achieving excellent performance in calibration and validation. These findings reinforce the influence of annual climatic conditions on the chemical and sensory composition of coffee. In particular, climate variations appear to have impacted the metabolism of key compounds responsible for modifying the beverage’s flavor and aroma. This study contributes to the understanding of the effects of environmental conditions and processing methods on coffee quality, aiding in the optimization of agricultural and post-harvest practices.