Effect of Mechanical Depulping on the Biochemical, Physicochemicaland Polyphenolic Constituents During Fermentation and Drying of Ghanaian Cocoa Beans

Abstract

This work investigated the effects of mechanical depulping (asa means of pulp pre-conditioning) on thechemical, physicochemical and polyphenolic constituents during fermentation and drying of Ghanaian cocoa beans. The fermentation study and the drying study were conducted using a 5x4 factorial experiment with the principal factors being;(a) concentration of depulped beans (0, 25, 50, 75 and 100%),(b) fermentation time (0, 2, 4 and 6 days) and(a) concentration of depulped beans (0, 25, 50, 75 and 100%), (b) drying time (0, 2, 4 and 6 days) respectively. Ripe cocoa pods were depulped using a mechanical depulper and the depulped beans mixed with undepulped beans in a pre-determined ratio prior to fermentation. All parameters were studied using standard methods. Mechanical depulping and fermentation influenced all the studied parameters.Protein content decreased from 16.23% at the beginning of fermentation to 13.64% by the sixth day of fermentation in undepulped beans.Potassium was the dominant mineral and iron the least.Depulping caused a decrease in the potassium (K) content from 1000.43 mg/100g at the start of fermentation to 718.18 mg/100g at the end of fermentation in undepulped beans. Changes in biochemical composition and physicochemical properties were variable during fermentation of the depulped beans. The pH decreased from 6.5 to 6.3 for samples containing 0% to 100% respectively at the beginning of fermentation.Depulping caused slight increases in pH from 5.7 at the end of fermentation in 0% depulped beans to 6.02 at the end of fermentation in samples containing 100% depulped beans. Reducing sugar increased from 157.33 mg/g at the start of fermentation to 304.95 mg/gbythe sixth day of fermentation in 0% depulped beans.Depulping caused slight decreases in reducing sugar content. Increasing fermentation and depulping resulted in an increase in FFA. The FFA content increased from 0.89% in 0% depulping to 0.94% in samples containing 25% depulped beans.All thetreatments (0%, 25%, 50%, 75% and 100%) depulped beansobtainedfermentation index of one (1) by the forth (4 th ) day of fermentation.Total polyphenols and o-diphenols reduced with respect to depulping and fermentation time.Total polyphenols decreased from 31.29 mg/gat the start of fermentation to 22.23 mg/gat the end of the fermentation process in undepulped beans.Depulping caused a reduction in total polyphenols from 22.23 mg/g in undepulped beans to 19.9 mg/gin 25% depulped beans. Depulping of cocoa beans caused an increase in pHfrom 5 to 6 during drying. Depulping caused a slight increase in pH from 5.46 by the fourth day of fermentation in undepulped beans to 5.78 by the fourth day of fermentation in samples containing 100% depulped beans, however the FFA content after drying was far below the stipulated 1.75%.The anthocyanins content of the beans varied significantly with increasing dryingtime and depulping. It decreased from 7.60 mg/gat the start of drying to 5.35 mg/gby the fourth day of drying in undepulped beans. Drying of cocoa beans showed no distinct trendfor lightness (L), redness (a) and yellowness (b) for all levels of depulped beans. Cut test on the samples showed that percentage of purple beans generally reduced with increasing depulping. These findings suggest that mechanical depulping influenced to a varying degree the chemical, biochemical and polyphenolic content of fermented and dried Ghanaian cocoa beans.