THESIS

1.4.2 Degree of hydrolysis
120
The degree of hydrolysis of the larger-scale samples was 4.74 ±
0.52 %, which was only 0.20% different from that of the experiment –scale (4.61 ±
0.43%). The addition of pullulanase to the gelatinized rice starch suspensions resulted
in a more runny solution after 16-hr of reaction, especially at larger-scaled of starch
solution. This was probably due to the higher amount of the rice starch solution more
accessible for pullulanase hydrolysis and produce short chain linear glucan.
Debranched rice starches, particularly non-waxy rice starch, have been found to be
useful for produce high yield of slowly digestible starch and resistant starch (King and
Tan, 2005). Guraya et al. (2001a) found that, the debranched starch formed a white
crystalline product with slowly digestible properties. They observed that both the
level
of enzyme and time allowed for debranching have a pronounced effect on the
amount of starch that
is debranched.
1.4.3 Degree of syneresis
The scale up hydrolyzed samples were then induced to 4°C for
16 hr. Afterwards, the freeze-thaw cycle (-10/30°C) was further applied to promote
syneresis of retrograded starches. Degree of syneresis in the larger-scale had higher
(56.66 ± 1.62) than the experimental-scaled (55.80 ± 2.43) but not significantly (P≥
0.05). This due to the differences for the degree of hydrolysis, that was affected the
retrogradation process during storage. The high degree of hydrolysis had high degree
of syneresis. Additionally, the
degree of syneresis (retrogradation) depends on starch
precipitation
or aggregation and gelation. Gidley and Bulpin (1989) described these
processes
in a phase diagram showing the effect of cooling aqueous solution of
synthetic
amylose. In general, shorter chain lengths favored precipitation and longer
chain lengths favor
gelation.