Evolution of cacao bean proteins during fermentation: a study by two-dimensional electrophoresis

The protein content of cacao (Theobroma cacao) beans was studied by quantit ative two-dimensional electrophoresis (2-DE) and by measuring total and pro tein nitrogen by the Kjeldahl method from the unfermented stage up to the s eventh day of fermentation. The major trends in evolution of protein concen tration were followed by measuring the intensities of some of the most abun dant bean polypeptides. During fermentation a biphasic proteolytic process was observed. Protein degradation was detected after two days of fermentati on, and was most pronounced during the third day. Following the initial pha se of degradation until the end of fermentation, very little further protei n degradation was observed, possibly due to the release of polyphenolic com pounds and their subsequent complexing with the remaining proteins. Total p rotein estimated by the Kjeldahl method decreased to 57% of the initial val ue during the fermentation period. The process of degradation is selective, with some polypeptides resisting more than others. The evolution of total protein and non-protein nitrogen content is also described. (C) 1999 Societ y of Chemical Industry.