Effect of morphology on water sorption in cellular solid foods. Part II: sorption in cereal crackers

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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 µm, 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 × 10-9 m/s2 (at 1% MC, 16% aw) to 7.6 × 10-10 m/s2 (at 20% MC, 86% aw). --------------------------------------------------------------------------------
Original languageEnglish
Pages (from-to)311-320
JournalJournal of Food Engineering
Volume109
Issue number2
DOIs
Publication statusPublished - 2012

Fingerprint

crackers
sorption
vapors
Food
Water
diffusivity
water
water activity
Porosity
Steam
Humidity
Sample Size
water content
sorption isotherms
Magnetic Resonance Imaging
sampling
porosity
Edible Grain
relative humidity
chemical derivatives

Keywords

  • moisture diffusivity
  • porous product
  • composite food
  • tortuosity
  • migration

Cite this

@article{53ed620210e54a05820b3fdf16238d79,
title = "Effect of morphology on water sorption in cellular solid foods. Part II: sorption in cereal crackers",
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 µm, 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 × 10-9 m/s2 (at 1{\%} MC, 16{\%} aw) to 7.6 × 10-10 m/s2 (at 20{\%} MC, 86{\%} aw). --------------------------------------------------------------------------------",
keywords = "moisture diffusivity, porous product, composite food, tortuosity, migration",
author = "D.C. Esveld and {van der Sman}, R.G.M. and M.M. Witek and C.W. Windt and {van As}, H. and {van Duynhoven}, J.P.M. and M.B.J. Meinders",
year = "2012",
doi = "10.1016/j.jfoodeng.2011.08.023",
language = "English",
volume = "109",
pages = "311--320",
journal = "Journal of Food Engineering",
issn = "0260-8774",
publisher = "Elsevier",
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}

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.; van As, H.; van Duynhoven, J.P.M.; Meinders, M.B.J.

In: Journal of Food Engineering, Vol. 109, No. 2, 2012, p. 311-320.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Effect of morphology on water sorption in cellular solid foods. Part II: sorption in cereal crackers

AU - Esveld, D.C.

AU - van der Sman, R.G.M.

AU - Witek, M.M.

AU - Windt, C.W.

AU - van As, H.

AU - van Duynhoven, J.P.M.

AU - Meinders, M.B.J.

PY - 2012

Y1 - 2012

N2 - 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 µm, 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 × 10-9 m/s2 (at 1% MC, 16% aw) to 7.6 × 10-10 m/s2 (at 20% MC, 86% aw). --------------------------------------------------------------------------------

AB - 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 µm, 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 × 10-9 m/s2 (at 1% MC, 16% aw) to 7.6 × 10-10 m/s2 (at 20% MC, 86% aw). --------------------------------------------------------------------------------

KW - moisture diffusivity

KW - porous product

KW - composite food

KW - tortuosity

KW - migration

U2 - 10.1016/j.jfoodeng.2011.08.023

DO - 10.1016/j.jfoodeng.2011.08.023

M3 - Article

VL - 109

SP - 311

EP - 320

JO - Journal of Food Engineering

JF - Journal of Food Engineering

SN - 0260-8774

IS - 2

ER -