Effects of Processing Time and Temperature on Flavanol and Procyanidin, Proanthocyanidin and Antioxidant Activity of Cocoa Bean in Taiwan

Abstract

Flavanol in cocoa is beneficial to cardiovascular health. This study investigated the effect of roasting conditions, temperature ranging from 110 to 150°C and time duration 15-35 min, on the level of flavanol and procyanidin (FP), total proanthocyanidin (PAC) and antioxidant activity of fermented cocoa beans in Southern Taiwan. The content of FP in unroasted and roasted cocoa bean was determined by the normal phase HPLC method and the antioxidant activity was assayed by DPPH and ABTS methods. High roasting temperature for long time decreased the content of FP and PAC in cocoa beans, where ranged from 55.30±1.95 mg (-)-epicatechin equivalents /g and 103.56±8.33mg procyanidin B1/g (at 110°C for 15 min) to 19.12±0.66 mg (-)-epicatechin equivalents /g and 51.58±0.86 mg procyanidin B1/g (at 150°C for 35 min), respectively. Meanwhile, as the roasting temperature rose, the DPPH and ABTS free radical scavenging ability of roasted cocoa bean extracts decreased gradually, varying from the maximum (IC50 = 104±2 µg/ml and 50.4±1.1mg TE/g) for unroasted bean to the minimum (IC50 = 144±4 µg/ml and 27.7±2.4 mg TE/g), and then slightly increased to IC50=134±4 µg/ml and 31.5±0.7 mg TE/g, respectively at most severe roasting treatment, showing the formation of melanoidins and polyphenols caused the synergistic effect, leading to the rise of the antioxidant activity. The first order kinetic reaction and the Arrhenius equation were applied to forecast the change of FP concentration during roasting. The activation energy of FP degradation is 11.2 kcal/mol. The obtained kinetic equation could be useful to predict the remaining amount of FP in cocoa beans under the designed experiment. The cocoa products with higher flavanol content and antioxidant activity could be possible by setting appropriate roasting conditions.