Dutching is a widely used industrial process for improving taste, dispersibility and coloring of the final product. Nevertheless, knowledge about the compounds causing a change in coloring is fragmentary. Therefore, the aim of this study was to identify polyphenol-derived chromophores, generated through alkalization. Because of low yields in alkalized cocoa and high reactivity of these compounds they were generated using alkalization models on the major single polyphenols of cocoa (+)-catechin and (-)-epicatechin as well as catechinic acid, which is a rearrangement product in alkaline milieu. The generated compounds have been isolated via color-activity guided fractionation and subsequently identified by means of LC-MS/MS analysis, 1D- and 2D-NMR, and electron paramagnetic resonance (EPR) spectroscopy. It was possible to detect and quantify four classes of chromophores, as well as their precursors in alkalized cocoa powders. The majority of the identified chromopohores showed a decrease in concentration by Dutching, which is explainable by accumulation to higher ordered chromophore oligomers, as shown by increase of the high molecular weight fraction isolated by means of ultrafiltration. With the gained knowledge it was possible to generate a potent polyphenol based red dye. In order to confirm the usability as well as pH stability of this red dye for food color enhancing it was tested on several food grade samples. These findings give a first insight into the formation of structures contributing to the red coloration of processed cocoa, which helps to optimize alkalization process parameters towards a better color design of cocoa powders.

Formation and structure determination of polyphenol-derived red chromophores: Enhancing the color of processed cocoa powders

2019 Spring National Meeting

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