Optimization of Ultrasound-Assisted Extraction and Rapid Resolution Analysis of Flavanols and Methylxanthines for the Quality Control of Cocoa-Derived Products

The aim of this study was to develop a rapid and reliable method to quantify cocoa methylxanthines, flavanol monomers, and its major procyanidins. To accomplish this goal, an ultrasound-assisted extraction process was optimized by response surface methodology. In addition, an improved separation of these compounds was carried out on a sub-2-mu m particles column while employing a conventional high-performance liquid chromatography (HPLC) instrument. Our results show that the highest extraction yields are obtained by using a 66:44 (v/v) ethanol/water mixture and performing the extraction at least during 20 min. The qualitative and quantitative analyses of cocoa metabolites were achieved in less than 12 min. Moreover, the optimized analytical approach was fully validated and applied to the analysis of cocoa samples collected at five different processing stages. The results show that the approach developed herein significantly increased the extraction efficiency, reaching concentrations approximately 20 % higher than that of the official Association of Analytical Community (AOAC) method for the analysis of polyphenols in cocoa-based matrices.