Influence of Environmental and Microclimate Factors on the Coffee Beans Quality (C. canephora): Correlation between Chemical Analysis and Stable Free Radicals

Abstract

The present study reports a physicochemical comparison of shade-grown and sun-grown coffee beans, under unripe, rip and roasted-ripe conditions, using electrical conductivity measurements, electron paramagnetic resonance (EPR), infrared spectroscopy (FTIR), and high performance liquid chromatography (HPLC). Moreover, the assessed physicochemical parameters were compared with organoleptic evaluations based on the Coffee Quality Institute protocol. The values found for electrical conductivity, leached potassium, and stable free radicals were respectively 29%, 31%, and 350% higher for shade-grown coffee beans, whereas polyphenol oxidase enzymatic activity was 23% lower. By contrast, FTIR and HPLC measurements identified higher chlorogenic acid and lipid contents in sun-grown coffee beans. Importantly, the sensorial grade attributed to roasted-ripe grains was 12% higher for sun-grown coffee. Our findings suggest that shade-grown coffee beans have undergone microorganismal activity and undesired fermentation during cultivation, which resulted in lower coffee quality. A correlation between a set of selected physicochemical properties and organoleptic properties was robustly

Antioxidant Activity and Stable Free Radicals in Robusta Green Coffee Genotypes/ Atividade antioxidante e Radicais Estáveis Livres em Genótipos de Café Verde Robusta

“…green and (b) roasted. Assessed g-factors were in the range of 2.0043 -2.0045, with a peak-to-peak line width of about 0.65 mT; these parameters are characteristic of stable free radical species previously described in coffee beans [22,24].The quantitative assessment of stable free radicals was carried out by double integrating the EPR spectra (intensity) and the results are collected in Table 2. Relative values vary in the range of 0.032 -0.083 a.u.…”

“…Taking this into account, the measured contents of 5-CQA (Table 1),for the studied genotypes, are in the range of47.2 -56.9 mg/g. BICHO et al [24,39] found values of 44.3 mg/g and 47.0 mg/g, respectively for the species Arabica (Brazil) and Robusta (India), where as ALVES et al [39] obtained values in the range of 44.8 -49.3 mg/g for Brazilian Robusta beans. From the results herein obtained, the genotypes Bamburral and Coringa present lower contents of this compound, whereas the others genotypes, with higher fractions, did not present statistical differences (p ≤ 0.05).…”

“…All spectra were collected in air atmosphere, at 25 oC, using a temperature and gas controller (NoxygenNOX-E.4-TGC, Germany),in the field range from 312 to 360 mT. Concentration of stable free radicals was assessed using total microwave absorption data evaluated by double integration of the first derivative of the EPR spectra [24,36]. The g-Factor values were obtained from the resonance condition according to KRAKOWIAN et al (2014) [36].…”

“…In this study, it was observed that the accumulation of stable radicals works as a defence/resistance mechanism of the plant to water stress. In another study, it was reported that during storage of the roasted bean, exposure to O2 is the main mechanism for generation of stable radicals through oxidation of the grain surface [24]. It is also known that stable free radicals increase continuously during the bean roasting and are associated with chemical components arising from oxidation reactions and melanoidin formation through the Maillard and caramelization reactions [55].…”

“…2021 coffee bean during storage and roasting [23]. Recently, ALVES et al [24] showed that the incidence of microorganisms presents in Robusta coffee grown under shade with high humidity increases the amount of these radicals with respect to the coffee grown in the sun. Thus, monitoring the evolution of the content of these stable free radicals has provided a way to assess the quality of the coffee beans during and after cultivation.…”