Post‐harvest pod storage: A method for pulp preconditioning to impair strong nib acidification during cocoa fermentation in Malaysia

Abstract

Abstract In Malaysia, pulp preconditioning by post‐harvest storage of cocoa pods leads to the reduction of nib acidification during subsequent fermentation, reduction of the acid note and an increase in cocoa flavour in the resulting raw cocoa. Data from several shallow‐box fermentations, with material from unstored and stored pods, are compared and interpreted, obtained in the years 1984 to 1987 in a cooperational investigation of the Malaysian Agricultural Research and Development Institute (MARDI), Malaysia, and the Botanical Institute, Technical University of Braunschweig (TUBS), FRG. Prior to and during fermentation, pulp volume and pulp sugars; pH value, acetic acid and lactic acid content in the pulp and nibs; and oxygen concentration and temperature in the mass were determined. Some flavour assessments from selected samples are given. The great reduction in pulp volume per seed rather than the decrease of pulp sugars per seed during pod storage was found to be of the most importance. Pulp‐volume reduction enhances mass aeration and increases the ratio of respiration to ethanol fermentation and its subsequent oxidation to acetic acid. As a consequence, the acidification of the seeds during the formative stages of flavour precursors (after the death of the seeds) is strongly reduced. With effectively dry stored pods (pulp volume per gram of seed ≤0·6 ml) the anaerobic phase during the initial stages of fermentation which is common with unstored pods is suppressed. Under these conditions the nib pH value does not fall below 5·0 and no drastic acid (and flavour) degradation at the end of fermentation is necessary to reduce the acidity in the seeds.