Identification of Adulterated Cocoa Powder Using Chromatographic Fingerprints of Polysaccharides Coupled with Principal Component Analysis

Abstract

A novel analysis method for identification of adulterated cocoa powder was established using high performance liquid chromatography (HPLC) fingerprint profiling coupled with principal component analysis (PCA). Polysaccharides were extracted from 11 batches of cocoa powder samples with hot water under ultrasound-assisted conditions and then completely hydrolyzed with sulfuric acid after enzymatic removal of proteins. The hydrolysates were analyzed by HPLC using precolumn 1-phenyl-3-methyl-pyrazolone derivatization to obtain the fingerprints of cocoa powder polysaccharides. The relative areas of 12 common characteristic peaks in the fingerprints and corresponding chromatogram data of adulterated samples obtained under the same chromatographic conditions were processed using PCA. The results showed that adulterated cocoa powder samples mixed with 15 % or more cocoa shell powder and 10 % or more exogenous plant material (including chestnut shell powder, longan shell powder, peanut shell powder, starch, wheat powder, or pumpkin powder) could be identified using this method.