Review on polyphenols in Theobroma cacao: changes in composition during the manufacture of chocolate and methodology for identification and quantification

Abstract Polyphenols have become an intense focus of research interest because of their perceived health-beneficial effects, such as anti-carcinogenic, anti-atherogenic, anti-inflammatory, anti-microbial, etc. Polyphenols in green and black tea, grape seeds, grapes and (red) wine have raised much attention but chocolate has not been investigated intensively up to now. This review is concerned with polyphenols in Theobroma cacao, the change in composition and quantity during fermentation, drying, and the manufacture of chocolate, as well as with analytical methods for isolation, characterisation and quantification. Cocoa beans are rich in polyphenols in particular catechins and proanthocyanidins. However, a sharp decrease in quantity occurs during fermentation and drying of cocoa beans and further retention has been reported during roasting. Characterisation and in particular quantification of polyphenols in chocolate has only been developed relatively recently. This work reviews further on the literature on the available methodology for analysis, quantification, isolation, purification, and structure elucidation of polyphenols in cocoa components and other commodities. Concerning the analytical methods main emphasis is put on HPLC as it is usually the method of choice due to its high resolution, high efficiency, high reproducibility and relatively short analysis time without restriction on sample volatility. Moreover, HPLC can be coupled to a variety of detectors such as UV–Vis, photodiode array (PDA), fluorescence, electrochemical (ECD), and mass spectrometry (MS). However, TLC as a screening method and capillary electrophoresis (CE) as a promising tool is taken into consideration as well. The characterisation and quantification of the polyphenol composition is amongst the first steps to be done to evaluate a putative contribution of chocolate to human health.