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Internal structure and water transport in endosperm and parchment of coffee bean

Alejandra Ramirez-Martinez 1
1 CGB - Couplages en Géomécanique et Biomécanique
LMGC - Laboratoire de Mécanique et Génie Civil
Abstract : The aim of this study is to describe the water mass transfer into the coffee bean. In order to achieve this objective, internal structure of coffee beans was studied with microscopy and stereoscopy. The results gave evidence of the coffee bean structure heterogeneity. Three structures at bean surface with mass transfer resistance potential were also studied: parchment, silver skin and endosperm. Sorption isotherms and water diffusion coefficient values of coffee different structures were obtained and they did not showed significant difference except parchment. An experimental technique to study the transfer of water into the parchment was proposed. In the endosperm, for water contents above 65%, a constant diffusion coefficient describes the kinetics of the whole bean. Below this water content, water diffusion coefficient values (with and without silver skin) were significantly lesser than those for the whole bean. This is firstly due to the reduction of the pore space occupied by water and to the augmentation of the bonding between the solid skeleton and water when water content decreases. A simple simulation is proposed however the set of results will allow to simulate coffee bean drying and to have information about the zones at high water activity. This information would help to diminish the risk of A. ochraceus development at drying. The contribution of parchment in the protection of the endosperm is highlighted.
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Submitted on : Wednesday, September 12, 2012 - 11:24:31 AM
Last modification on : Wednesday, May 29, 2019 - 10:04:03 AM
Long-term archiving on: : Thursday, December 13, 2012 - 3:45:24 AM

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  • HAL Id : tel-00731154, version 1

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Alejandra Ramirez-Martinez. Internal structure and water transport in endosperm and parchment of coffee bean. Mécanique des matériaux [physics.class-ph]. Université Montpellier II - Sciences et Techniques du Languedoc, 2011. Français. ⟨tel-00731154⟩

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