Drying with chemical reaction in cocoa beans

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Desirable flavor qualities of cocoa are dependent on how the cocoa beans are fermented, dried, and roasted. During fermentation and drying, polyphenols such as leucocyanidin and apecatechin are oxidized by polyphenols oxidase to form o-quinone, which later react nonenzymatically with a hydroquinone in a condensation reaction to form browning products and moisture. The objective of this article is to model the cocoa beans drying together with the browning reaction. A Luikov drying model for the moisture and a simple Fick's law diffusion model combined with first-order reactions for both the enzymatic oxidation and nonenzymatic condensation reactions were constructed. Both models were used to identify moisture diffusivity coefficient and total polyphenols diffusivity in cocoa beans from experimental drying and polyphenols degradation data and published kinetic data of the reactions. The theoretical drying model fitted the experimental cocoa bean drying curves with low mean square of residuals. The polyphenols diffusion and reaction model also fitted the experimental polyphenols degradation curves with minimum mean residual squares. The rate of polyphenols degradation in the cocoa beans increases at higher temperature and higher relative humidity. This is because the increasing reaction rate of polyphenols oxidation reaction as well as higher moisture diffusion at higher relative humidity and temperature. The effective moisture diffusivity in cocoa beans is estimated to be between 8.194 × 10-9 and 8.542 × 10-9 m2·s-1, which is of the same order of magnitude as published data. The effective total polyphenols diffusivity is estimated to be between 8.333 × 10-12 to 1.000 × 10-11 m2·s-1 with minimum mean residual squares. It is three orders of magnitude less than the estimated moisture diffusivity because of the larger polyphenols molecules. The estimated polyphenols diffusivity is very close to those published in the literature for sorption and ultrafiltration processes.

Original languageEnglish
Pages (from-to)867-875
Number of pages9
JournalDrying Technology
Volume25
Issue number5
DOIs
Publication statusPublished - May 2007

Fingerprint

Cocoa
Polyphenols
drying
Chemical reactions
chemical reactions
Drying
moisture
diffusivity
Moisture
degradation
humidity
Condensation reactions
condensation
Degradation
oxidation
fermentation
Atmospheric humidity
oxidase
quinones
curves

Keywords

  • Browning reaction
  • Polyphenols diffusivity

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)

Cite this

Drying with chemical reaction in cocoa beans. / Wan Daud, Wan Ramli; Meor Talib, Meor Zainal; Kyi, Tin Mar.

In: Drying Technology, Vol. 25, No. 5, 05.2007, p. 867-875.

Research output: Contribution to journalArticle

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