Acidification, proteolysis and flavour potential in fermenting cocoa beans

Abstract

AbstractCocoa fermentations in Ghana and Trinidad as well as anaerobic fermentation‐like incubations of fresh cocoa beans in Germany were carried out under controlled conditions. Samples of beans were taken during the course of these treatments and determinations were made as to acidification (pH, acetic acid content), proteolysis (free α‐amino nitrogen, peptide nitrogen and SDS electrophoresis of the protein peptides) and flavour potential (gas chromatography of the highly volatile compounds, in particular isopentanal and organoleptic analysis after thin layer roasting). A positive correlation between acidification, proteolysis and the development of flavour potential during anaerobic fermentation can be demonstrated in principle. However, the flavour potential is increased if the temperature rise is comparatively slow in both normal fermentation and laboratory incubation. Strong acidification and high accumulation of amino acids and peptides were not essential for a good flavour potential. The isopentanal content proved to be a useful indicator of the progress of normal fermentation in the tropics. These findings can be interpreted on the basis of earlier results about germination‐like processes in the protein vacuoles, pre‐ and post‐mortem subcellular structures and the special characteristics of acetic acid diffusion. Conclusions which are relevant to the practice of cocoa fermentation are discussed in more detail.