2.4. Structure assessment by microcomputed X-ray tomography
X-ray tomography scans were acquired with a 1172 MCT system
(Brüker MicroCT, Kontich, Belgium) with an X-ray source of 40 kV and
100 μA. For a pixel size of 5 μm, the camerawas set up at 2000 × 2096 -
pixelswith an exposure timeof 295 ms. Scanswere performed on a representative
specimen of each experiment over 180°, the rotation step
was 0.4° and the frame averagingwas 10. The reconstruction of datasets
was performed on average over 450 slices with Brüker MicroCT recon
software (version 1.4.4.).
3D image analysis was performed on 10 μm per pixel datasets with
CTAn software (version 1.7.0.3, 64 bit, Brüker MicroCT, Kontich,
Belgium). After segmentation of the grey level images at 40, the selection
of the volume of interest was performed through the shrink-wrap
function to adjust to the surface or contour line of extruded pellets.
The images were reloaded and the volume of interest was used as a
mask. The images were segmented at a grey level of 40. The porosity
Table 1
Summary of the composition of the extruded products.
Recipe Whole
wheat
flour (%)
Refined
wheat
flour (%)
Corn
flour
(%)
Soy
flour
(%)
Added fibres
(oat bran or
wheat bran) (%)
Wheat based recipe 40
40 30 18 0
60 20 8 0 10
80 10 0 20
0
Corn based recipe 64 0
50 14
0 0 44 34 20
38 26
32 32 (only for
wheat bran)
a) 0% 10% 20%
b) 0% 14% 32%
c) 0% (diameter: 5.5mm) 32% (diameter: 3.5mm)
Fig. 2.
2.4. Structure assessment by microcomputed X-ray tomographyX-ray tomography scans were acquired with a 1172 MCT system(Brüker MicroCT, Kontich, Belgium) with an X-ray source of 40 kV and100 μA. For a pixel size of 5 μm, the camerawas set up at 2000 × 2096 -pixelswith an exposure timeof 295 ms. Scanswere performed on a representativespecimen of each experiment over 180°, the rotation stepwas 0.4° and the frame averagingwas 10. The reconstruction of datasetswas performed on average over 450 slices with Brüker MicroCT reconsoftware (version 1.4.4.).3D image analysis was performed on 10 μm per pixel datasets withCTAn software (version 1.7.0.3, 64 bit, Brüker MicroCT, Kontich,Belgium). After segmentation of the grey level images at 40, the selectionof the volume of interest was performed through the shrink-wrapfunction to adjust to the surface or contour line of extruded pellets.The images were reloaded and the volume of interest was used as amask. The images were segmented at a grey level of 40. The porosityTable 1Summary of the composition of the extruded products.Recipe Wholewheatflour (%)Refinedwheatflour (%)Cornflour(%)Soyflour(%)Added fibres(oat bran orwheat bran) (%)Wheat based recipe 4040 30 18 060 20 8 0 1080 10 0 200Corn based recipe 64 050 140 0 44 34 2038 2632 32 (only forwheat bran)a) 0% 10% 20%b) 0% 14% 32%c) 0% (diameter: 5.5mm) 32% (diameter: 3.5mm)Fig. 2.
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