Soluble albumin and biological value of protein in cocoa (Theobroma cacao L.) beans as a function of roasting time

An association has been identified between the extent of roasting and the amount of extractable protein from the cocoa bean, its nutritive value, and the sensorial quality of the liquor. Cocoa nibs from fermented seeds (Theobroma cacao L.) were precision-roasted at 150 degrees C for 0, 30, 34, 38, 42, and 46 min and the protein fraction extracted. From the beginning of roasting, until minute 38, about 87% of the proteins were extractable, but the extractability substantially decreased to 72.7% at 42 min and to 65.3% at 46 min. Both total soluble protein determination and albumin concentration of the roasted nibs diminished slightly until minute 38, when acceptable sensory characteristics were obtained for the liquor. Both total nitrogen and capillary-electrophoretic separation and quantification of the albumin showed that the amounts of extractable protein in this fraction consistently followed a cyclic pattern until minute 42, irreversibly decreasing thereafter. Biological evaluation of the protein from the cocoa nibs roasted for the various times showed that at the point that the sensory rating approached that of a commercial liquor, the albumin content and nutritive value were still high. The findings suggest that with moderate, uniform roasting it may not be necessary to sacrifice the protein's biological value for the sensorial attributes of chocolate in a standard commercial roast.