Perfecting a method of micro-analysis of water and acetic acid in a cocoa bean in the course of drying: applying to determine transportation coefficients

摘要

This article is about the study of the diffusion of water and acetic acid in a grain of cocoa in course of drying. The authors present a method of microanalysis which enables the analysis of each little slice of the grain: a precise measurement of each slice is realised in view of the analysis from the centre to the surface of the grain with the aid of a cutting apparatus, designed and realised to this effect. At each instant of the drying process, the profiles of water and acetic acid contents are then determined. A one dimensional diffusion model enables a shell by shell evaluation of the diffusion of water and acid in the cocoa grain. The results obtained show an augmentation of transport coefficients in course of drying. We however observe a decrease of the diffusion coefficient of water to the low moisture content : what makes us think of the appearance of crusting phenomenon.