Structural and chemical changes in cocoa (Theobroma cacao L) during fermentation, drying and roasting

Cocoa seeds and pulp were fermented for 144h, followed by natural drying. T he tegument was removed and the cotyledons were broken into nibs which were roasted at 150 degreesC for 30 min. Non-fermented material, material ferme nted for 24, 48 and 72h, material fermented for 144h and then dried, and al so the roasted nibs, were all prepared for chemical and microscopic analyse s. Light microscopy revealed the presence of anionic and cationic residues and of neutral sugars. During fermentation there was a reduction in the cyt oplasmic content of phenolic compounds and in the number of protein bodies. The cell wall showed a reduction in anionic residues and a loss of crystal linity. These alterations were maximum after 72 h. Drying and roasting incr eased the number of damaged cells and reduced the amount of cytoplasmic mat erial. The chemical analyses generally confirmed the microscopy results. Th e concentration of amino-terminal groups and total free amino acids increas ed during fermentation (up to 72 h), but returned to the initial values aft er roasting. The principal chemical changes were related to reducing sugars , free amino acids, proteins and phenols, and PCA was suggested as a useful tool to compare different samples. Microscopic analysis revealed the degra dation of protein and phenolic bodies and cellular damage during roasting. (C) 2000 Society of Chemical Industry.