2.4.3. Particle size analysis
Beckman Coulter LS 13 320 laser diffraction particle size analyzer
(Beckman Coulter Inc., Brea, CA, USA) equipped with tornado
dry powder system (DSP) was used to measure the particle size of
dietary fibre from hulls. Fiber samples were analysed in triplicate,
using approximately 10 g of sample in each test. The DSP is an efficient
dry dispersing system without using pressurised air, so particle
attrition is minimised. The vacuum created a flow of air through the sample holder. High shear forces were formed which disperse
the powder. The analyzer was to measure the particle scattering
intensity angular pattern to obtain size distribution. The light scattered
from the particles was focused onto detectors at different
scattering angles. Each detector recorded the amount of energy
falling onto its light sensitive zones.
2.4.4. Water absorption index (WAI) and water solubility index (WSI)
measurement
Two centrifuge tubes were weighed separately with individual
weights. 2.5 g of sample was then put in each tube. 30 mL of distilled
water were added and stirred with sample to avoid lumps.
The tubes were closed and placed in the water bath with 25 C
for 20 min. Those tubes were centrifuged at 5000 rpm for 10 min.
The water was then decanted from the tube without loss of solids.
Finally, the tube and residues were weighed out. The WAI was calculated
as following equation: