The protein content of cacao (Theobroma cacao) beans was studied by quantitative two-dimensional electrophoresis (2-DE) and by measuring total and protein nitrogen by the Kjeldahl method from the unfermented stage up to the seventh day of fermentation. The major trends in evolution of protein concentration were followed by measuring the intensities of some of the most abundant bean polypeptides. During fermentation a biphasic proteolytic process was observed. Protein degradation was detected after two days of fermentation, and was most pronounced during the third day. Following the initial phase of degradation until the end of fermentation, very little further protein degradation was observed, possibly due to the release of polyphenolic compounds and their subsequent complexing with the remaining proteins. Total protein estimated by the Kjeldahl method decreased to 57% of the initial value 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 Society of Chemical Industry.