Changes in Nib Acidity, Proteolysis and Sugar Concentration as Influenced by Pod Storage and Roasting Conditions of Fermented Cocoa (Theobroma cacao) Beans

Abstract

Changes in nib acidity, protein and sugar concentration during roasting of pulp pre-conditioned and fermented cocoa (Theobroma cacao) beans were investigated. A 4 × 4 full factorial design with the principal experimental factors as pod storage (0, 3, 7 and 10 d) and roasting time (0, 15, 30 and 45 min) were used. The roasted samples were evaluated for pH, titratable acidity, protein content and sugars concentrations using standard methods. Increasing pod storage caused consistent increases in pH with concomitant decreases in titratable acidity, whereas increasing roasting time caused only marginal and insignificant changes in pH but significantly decreased the titratable acidity. The protein content decreased significantly (P < 0.05) with increasing pod storage and roasting time. Reducing sugars increased marginally with increasing pod storage treatments whiles increasing roasting time significantly (P < 0.05) decreased the reducing sugars of the beans for all pod storage. The non-reducing sugar and total sugar content of the beans decreased significantly from 3.493 mg/g to 2.641 mg/g and from 9.284 mg/g to 8.891 mg/g, respectively, for pods stored from 0 to 10 days while roasting time caused slight decreases in non-reducing sugars with a considerable decrease in total sugars. Pod storage up to seven days decreased considerable the nib acidity (non-volatile acids), non-reducing sugars and total sugars while roasting up to 45 min at 120 °C caused dramatic decreases in the nib acidity and reducing sugars with only marginal decreases in non-reducing sugars and total sugars.