Proposal for a semi-quantitative method for the determination of volatile compounds in cocoa liquors

Abstract

Seventy-four volatile compounds were identified and quantified from cocoa liquors of the ICS 95 and TCS 01 varieties produced in the department of Santander, Colombia. The compounds were extracted using the solid phase microextraction with head space (SPME-HS) technique, and identified by gas chromatography coupled to mass spectrometer (GC-MS) by comparing the mass spectra of each compound in the Wiley 275L library of mass spectra and the Kovats retention index (IK) ratio. A semi-quantitative method was proposed that included toluene as an internal standard to normalize the degree of recovery between samples and a response factor for each family, calculated using a compound characteristic of that functional group. The results associated with response factors for each family or group of compounds such as alcohols, acids, aldehydes, ketones, esters and pyrazines (2.19, 1.02, 2.84, 0.38, 6.38, 0.88 respectively) were different between families, however, there was no difference between compounds within the same family. The implemented method obtained a DOD and DML of 0.024 µg/kg and 0.037 µg/kg respectively and an accuracy expressed as percentage recovery (of characteristic compounds per family) of 96% on average. According to the precision of the method, the results show that the concentrations have an average coefficient of variation (%CV) of 7.38% assuring repeatability and good precision. Finally, for the analyzed and quantified samples, it was found that the compounds with higher concentration were acetic acid (42.633 mg/kg), 2-phenylethyl acetate (29.44 mg/kg), 2.3-butanediol (345.39 mg/kg), 2-phenylethanol (12.595mg/kg) and 2.3.5.6-tetramethylpyrazine (8.601 mg/kg).