3.1. Effects of superfine grinding on particle-size distribution and
starch damage of WWF
The particle-size distributions of WWFs with varying mean
particle sizes (MZ) are shown in Fig. 1. The MZ of WWF decreased
from 125-mm to 43-mm with the increase in grinding time from
5 min to 20 min. The distribution profile of the 125-mm group was
similar to a gaussian distribution in the range from 0 mm to
1000 mm. All the WWF particles in the 96-mm group were smaller
than 700 mm, and its profile showed a larger percentage in the
range of 0e75 mm compared to the 125-mm group. Most of the
WWF particles from the 72-mm group could pass through the 400-
mm sieve, and 80% of the particles were distributed in the range
from 0 mm to 100 mm. The 43-mm group showed the smallest MZ
among four groups, and 90% of the particles could pass through the
75-mm sieve. These results indicated that compared to the reconstituted
WWF by fine grinding of millfeeds using a lab mill grinder
(Niu et al., 2014a), superfine grinding was more effective to reduce
the particle size of WWF and wheat bran.
Starch damage, which increases water absorption in flour, can
cause aqueous extractability and rapid susceptibility to enzymatic
digestion. For noodle products, if starch damage is excessive, the
noodle dough tends to fragment more when mixing and the texture
of noodle may become less firm (Okusu et al., 2010). As shown in
Table 1, after going through the superfine grinding process, all
WWF groups showed significantly higher starch damage than the
SGF group. The starch damage value significantly increased from
21.06% in the 125-mm group to 26.03% in the 43-mm group with the
increase in the duration of the superfine grinding process. The results
implied that the starch damage of WWF was significantly
affected by the superfine grinding process. The changes might exert
some effects on the noodle-making properties of WWF