Journal Article

PreJuSER-17338

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Effect of morphology on water sorption in cellular solid foods. Part II: Sorption in cereal crackers

Esveld, D. C. ; van der Sman, R.G. M. ; Witek, M. M. ; Windt, C. W.FZJ* ; van As, H. ; van Duynhoven, J. P. M. ; Meinders, M. B. J.

2012
Elsevier Science Amsterdam [u.a.]

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Please use a persistent id in citations: doi:10.1016/j.jfoodeng.2011.08.023

Abstract: Experimental dynamical moisture profiles of crackers with a fine and coarse morphology are successfully predicted using a pore scale network model. Experimental profiles are obtained using a single point imaging (SPI) NMR technique that enables 3D mapping of the moisture content of relatively immobile water at low water activity.The relative vapor conductivity trough the structure is 33% and 64% for the fine and coarse structured crackers, respectively. It can be argued that this is due to their difference in cell connectivity and not directly related to their difference in average cell diameter (0.33 and 0.75 mm, respectively). It was found that the retarded local sorption dynamics of the solid matrix has a noticeable influence on the moisture profiles that arise in the first hours. This is crucial for the moisture sorption dynamics of sub centimeter size samples, for which there is a distinct non-equilibrium between the vapor and the sorbed water phase. The local sorption at low water activity is a factor 3 faster for the fine structure cracker compared to the coarse one. This is due to their differences in average lamellae thickness (54 and 93 mu m, respectively).However, for the description of the overall moisture sorption dynamics of the few cm thick samples, on a time scale of days, it valid to assume local equilibrium and to use an effective diffusivity model. The relative vapor conductivity together with the porosity and the derivative of the sorption isotherm determines the effective moisture diffusivity for these open structures, which is a factor 3 lower for the fine structured cracker compared to the coarse one. The single sided moisture sorption in the 2.5 thick cracker samples is not even completed after 5 days, mainly because at higher water content (near 20%) there is very little gradient in relative humidity to drive the vapor transport. This is reflected in the predicted effective moisture diffusivities which for the coarse cracker decrease from 16 x 10(-9) m/s(2) (at 1% MC, 16% a(w)) to 7.6 x 10(-10) m/s(2) (at 20% MC, 86% aw). (C) 2011 Elsevier Ltd. All rights reserved.

Keyword(s): J ; Network model (auto) ; Porous media (auto) ; Moisture sorption (auto) ; Cellular structure (auto) ; Effective diffusivity (auto) ; Cereals (auto) ; MRI (auto)

Note: This work was supported by Unilever R&D (Vlaardingen, The Netherlands) in the Dutch SENTER/IS program (Stable Textures in Health Snacks, IS42042.) Nic Franciosi (Unilever) is acknowledged for skillfully preparing the crackers.

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Contributing Institute(s):

1. Pflanzenwissenschaften (IBG-2)

Research Program(s):

1. Terrestrische Umwelt (P24)

Appears in the scientific report 2012

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Database coverage:
; BIOSIS Previews ; Current Contents - Agriculture, Biology and Environmental Sciences ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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