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Dynamic volume change measurements of cereal materials by environmental scanning electron microscopy and videomicroscopy
Author(s) -
TANG X.,
DE ROOIJ M. R.,
VAN DUYNHOVEN J.,
VAN BREUGEL K.
Publication year - 2008
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.2008.01962.x
Subject(s) - relative humidity , scanning electron microscope , equilibrium moisture content , desorption , volume (thermodynamics) , sorption , moisture , shrinkage , chemistry , isotropy , humidity , analytical chemistry (journal) , thermal diffusivity , materials science , thermodynamics , composite material , optics , chromatography , physics , adsorption , organic chemistry
Summary Moisture migration induced volume change in cereal materials was studied by environmental scanning electron microscopy, videomicroscopy and stereoscopy. It is shown that the in situ volume change can be monitored by the changes of projection area with the assumption of isotropic swelling/shrinkage. The projection area change from videomicroscopy matches well with the volume change by stereoscopy after dimensional normalization. The arbitrary volume values in between two relative humidity levels are available by interpolating the equilibrium volumes at beginning and ending. The sorption/desorption curves were fitted by the ‘parallel exponential kinetics’ model, which described two independent, parallel processes as ‘slow’ and ‘fast’. In the low relative humidity range, sorption curves match well with the ‘parallel exponential kinetics’ model and the two parallel processes tend to be identical when relative humidity increases. The diffusivity of water moisture in a cracker, which was estimated by the half‐equilibrium principle, has a strong dependence on relative humidity.