Polyphenols are phytochemicals responsible for the astringency, bitterness, green flavours and antioxidant activities in cocoa (Theobroma cacao) beans. These are degraded during fermentation, drying and roasting affecting the antioxidant activity of the beans. However, the extent of degradation of phenolics during roasting remains unknown. This work was aimed at investigating the changes in total polyphenols, anthocyanins, o-diphenols and antioxidant activity (free-radical scavenging activities) during roasting of pulp pre-conditioned and fermented cocoa. A 4×4 full factorial design with the principal experimental factors as pod storage and roasting time were used. Samples were analyzed for total polyphenols, o-diphenols, anthocyanins and antioxidant activity using standard analytical methods. Variable decrease in total polyphenols, o-diphenols and anthocyanins were observed with increase in pod storage and roasting durations. However, variable trends were observed for the % free-radical scavenging activities. The total polyphenols, anthocyanins and o-diphenols in the cocoa beans after 45 minutes roasting decreased from 132.24 to 57.17 mg/g, 6.71 to 1.07 mg/kg and 15.94 to 8.25 mg/g respectively for 0, 3, 7 and 10 days pod storage treatments. The total polyphenols for the fermented, dried and unstored cocoa beans was 132.25 mg/g which reduced to 122.14 mg/g (7.642% degradation), 116.721 mg/g (11.7% degradation) and 92.22 mg/g (30.3% degradation) for pod stored for 3, 7 and 10 days respectively. Increasing roasting time caused continuous decreases in the % free-radical scavenging activity from 89.10% to 74.31% after 45 minutes for the unstored pods. Pulp pre-conditioning by pod storage and roasting duration could be used to reduce the astringency and bitterness caused by polyphenols, o-diphenols and anthocyanins in cocoa beans whilst increasing the antioxidant activity imparted by cocoa.

Roasting effects on phenolic content and free-radical scavenging activities of pulp pre-conditioned and fermented cocoa (Theobroma cacao) beans

249th National Meeting (2015)

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