Research on Quantitative Determination of the Cocoa Shell Content in Cocoa Powder Products by UPLC-Q-TOF MS/MS

An assay combined ultra performance liquid chromatography-quadrupole-time of flight-tandem mass spectrometry (UPLC-Q-TOF MS/MS) with the multivariate statistical analysis methods including principal component analysis and orthogonal partial least squares-discriminate analysis was established for screening and identifying the characteristic markers of cocoa shell relative to cocoa powder, which could be used to quantitatively detect the content of cocoa shell in cocoa powder. The cocoa beans from Ecuador were selected as the research object, and the results showed that there was a great difference between cocoa powder and cocoa shell. One characteristic marker was identified as nigakilactone Ⅰ. There was a good linear relationship between the peak area of nigakilactone Ⅰ and the content of cocoa shell when the content of cocoa shell in cocoa powder was in the range of 1%-50%, the correlation coefficient was greater than 0.999 9. The detection limit and quantitative limit were 0.3% and 1%, respectively. In addition, this method was used for blind sample verification and commercial sample testing. The blind sample verification results showed that the detection content was basically consistent with the actual adulterated content, and the detection content of cocoa shell ranged from 2.51% to 9.03%. This method has high accuracy and high sensitivity, which can be used for identification of commercial cocoa powder adulteration.