Evaluation of cocoa products quality and authenticity by DART/TOF-MS

Abstract

Cacao and cocoa products are worldwide important commodities, which are often a subject of adulteration. Therefore, a sufficient and reliable analytical technique is required to provide fast screening results, which will accommodate the need to reveal adulteration and evaluate the quality of selected cocoa products in real time. The goal of this paper is to validate and optimise settings of the DART (direct analysis in real time) technique coupled with TOF-MS. The ionisation mode, ionisation temperature and type of solvent for sample extraction were optimised. Characteristic compounds of cocoa products (theobromine, caffeine, phenolic and flavonoid compounds) were determined and quantified in a set of 17 and 12 samples of cocoa powders and instant cocoa beverages, respectively. Quantitative analysis of theobromine and caffeine applying DART was evaluated as well and obtained data sets were compared with those obtained from HPLC measurements. The correlation equation between these two methods, for each compound and product, is as follows: theobromine: cocoa powders: DART = 1.6394 × HPLC – 1.4353; cocoa drinks: DART = 1.0385 × HPLC – 0.019 and caffeine: cocoa powders: DART = 1.0234 × HPLC – 0.0195; cocoa drinks: DART = 0.7909 × HPLC +0.0054. Mass spectra data was statistically processed applying PCA (principal component analysis). In conclusion, the fast DART/TOF-MS screening technique displays a great potential to evaluate the quality and authenticity, i.e. identify and quantify characteristic compounds of cocoa products.