Differentiation of cocoa nibs from distinct origins using comprehensive two-dimensional gas chromatography and multivariate analysis

Abstract

Headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography was used for identification of volatiles compounds responsible for differentiation between cocoa nibs from Brazil and Ivory Coast. The unfolded GC×GC with Flame Ionization Detector (FID) chromatograms were first aligned using the correlation optimization warping (COW) algorithm and normalized. After that, Fisher ratio was calculated for each variable, and a threshold value was chosen to select the variables that best promote a separation of nibs samples from different sources in a principal component analysis (PCA) model. To identify the relevant compounds for the separation, representative samples of each source were analyzed in the same conditions by GC×GC with detection by quadrupole mass spectrometry. Finally, the average peak volumes for each key compound obtained for both classes were compared using a Student t-test and it was possible to identify 15 volatile compounds responsible for differentiation between cocoa nibs from Brazil and Ivory Coast.

Keywords: Cocoa nibs; Comprehensive two-dimensional gas chromatography; Fisher ratio; Principal component analysis; Solid phase microextraction.