THESIS

1.3.1 Degree of pullulanase hydrolysis
113
Degree of hydrolysis of 15% (w/w) gelatinized high amylose rice
starch reacted with 0 to 16 unit/g starch of pullulanase for
16 hr are shown in Figure
25. The amount of hydrolysis degree was defined by measuring the concentration of
reducing groups which were freed by alpha-1,6-D-glucanohydrolase activity by
means of Park and Johnson method. The study found that an increasing of enzyme
concentration
from 8 to 14 unit/g starches provided the degree of hydrolysis to
gradually increase from 2.46 to 5.21 %. However, there was no significantly increased
in degree of hydrolysis for the rice starch samples treated with 16 unit/g starch. This
indicated that the starch was completely debranched.
When the starch is completely debranched, the monitored
measurement
will no longer change. The debranched starch will typically have an
average chain length of 14 to 25 glucose units and less than about 0.2 %, particularly
less than about 0.1 % alpha-1,6-D-glucosidic bonds linkages( Hizukuri et al. 1981).
De gree of pullu lana se hydrolysis
( % )
6
5
4
3
2
1
0
0 8 10 12 14 16
Figure 25 Effect of pullulanase enzyme concentration (0 to 16 unit/g starch) on
degree of pullulanase hydrolysis of 16 hr debranching of 15 % HARS
preheated at 121°C for 30 min
Enzyme concentration (unit/g starch)