Análise química e atividade antioxidante de quatro amostras de café (Coffea arabica)

Abstract

The ground coffee consumed in Brazil has a poor standardization and there is a lack of a rigid quality control in this kind of coffee. The present work compared four commercial brands of cerrado coffee (A, B, C and D) with a standard cerrado coffee. We intended to establish a quality relationship between the standard coffee and the commercial ones that are sold in Triângulo Mineiro MG and Southern of Goiás GO regions. Brands A and C showed humidity content above the permitted by ANVISA (National Agency for Sanitary Vigilance). Brands A and B showed a higher soluble solids content, witch is desirable, adding body to a quality drink. All samples showed caffeine levels within permitted range by actual legislation, and, brand C showed the lowest caffeine level and brand D showed the highest level, what suggests that this brand could have more robusta grains on its composition. The protein levels for the standard coffee and ground samples varied from 16.56 to 18.69% and for the soluble fraction varied from 21.88 to 25.25%. All samples presented scavenger activity against free radical DPPH. and brand D and the standard coffee showed the highest inhibition percentage. The standard coffee also presented the highest number of volatile compounds identified by GC/MS, and brands C and D showed the lowest levels for these constituents. The FTIR identified active functional groups for all samples, in the ground coffee as in the soluble drinkable extract, but no one brand showed properties that could be used in its differentiation. The 1H NMR of all soluble fractions allowed the observation of signals referring to quinic acid, caffeine, chlorogenic acids, formic acid and trigoneline. In brand A, was observed an intense signal near 0.9 to 1.2 ppm, peculiar to CH3 and CH2 protons. The highest chlorogenic acid level was in standard coffee, evidenced by a signal near 2.0 ppm. The solid state 13C NMR allowed the observation of peculiar signals of caffeine, chlorogenic acid and quinic acid in all samples, including the standard, but it was not possible to distinguish among them.