Impact of alkalization conditions on the phytochemical content of cocoa powder and the aroma of cocoa drinks

Abstract

Alkalization is an important process in cocoa powder production that affects color and flavor. In this study, the impact of alkalization temperature (60, 70, 80, 90, 100 °C), NaOH concentration (0.59, 1.17, 2.34, 3.59% w/w of cocoa powder) and alkalization time (1 and 10 min) on the physicochemical properties (pH, color) and phytochemical profile (theobromine, caffeine, epicatechin, catechin) of cocoa powder were investigated, while the aroma was studied on the corresponding cocoa drinks. High-performance liquid chromatography coupled to an ultra-violet detector (HPLC-UV) was used for screening the non-volatiles and headspace solid - phase microextraction - gas chromatography - mass spectrometry (HS-SPME-GC-MS) for the aromatic compounds. Major changes of the cocoa properties occurred during the first minute of alkalization. Increase of temperature and alkali concentration generally reduced the levels of epicatechin and the lightness (L*), while the pH of the cocoa powder was affected by changing the alkali concentration. On the other hand, the reddish (a*) and yellowish (b*) color component values and theobromine levels were not significantly affected by varying temperature and alkali concentration. A higher temperature did not affect the concentration of the volatile compounds, while a decrease in certain chemical classes was observed by increasing the alkali concentration.