Development of an analysis method to quantify chlorogenic acids in coffee

Abstract

A method to analyze chlorogenic acids in coffee was developed and validated, using the same methodology for caffeine extraction: water at 78°C for 60 min; a 10-fold dilution and obtention of the second derivative’s spectrum to quantify caffeine and chlorogenic acid contents in coffee. The proposed method has a linear scope, at 357.16 nm, between 8 and 120 mg l-1 of clorogenic acid. Caffeine, tannic acid, saccharose and albumen, usually present in coffee, do not present interference problems. The extraction of chlorogenic acid of the coffee must be made without addition of substances that vary the acidity of the solution, since at pH smaller or greater than 5.5-6.0 the results are significantly different. The calibration chart is homocedastic and the limits of detection and quantification are 0.002 and 0.006 mg l-1, respectively. The slope of the function of recovery (0.97±0.07) and its intercept (0.01±0.05) fit the ideal curve, which implies a good recovery with the proposed method. The method developed was applied to different samples of roasted commercial coffee, to samples of 2 varieties of coffee, roasted at temperatures of 195-210°C during 9-11 min and finally to gold coffee of different varieties.