THESIS

1.2.7 Physicochemical properties of RS III samples
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Table 14 shown the physicochemical properties of RS III from
pullulanase debranched (0 to 48 hr) of 15% rice starch slurry preheated at 75 o C, 95 o C
and 121 o C for 30 min. The production yields and water activity in the RS III samples
were not significantly different (P≥0.05) among treatments. The RS III samples had
production yield and water activity between 88.13-89.87% and 0.436-0.649% for 0 –
48 hr debranched of rice starch slurry preheated at 75 o C, 95 o C and 121 o C for 30 min,
respectively.
The moisture content in the 121 o C preheated samples were
significantly lower (P≤0.05) than the 75 o C and 95 o C preheated samples. The moisture
content was 5.17 -10.50%, 10.48 -12.22% and 10.67 -12.55% for 121 o C, 75 o C and
95 o C preheated rice starch sample, respectively. It could be clearly seen that the high
degree of syneresis trend to lower percentage of moisture content and water activity.
All color data was expressed by the Hunter system. The Hunter
L*, a* and b* values correspond to lightness, redness, and yellowness, respectively.
Hunter L * , a*, b * values of RS III samples were affected by hydrolysis time (Table
14). The result indicated that the color of the RS III from 0 to 16 hr of hydrolysis in
both of preheated rice starch at 75 o C, 95 o C and 121 o C were significantly (p≤0.05)
lightener than the 24 to 48 hr hydrolysis rice starch samples. Native high amylose
rice starch had the highest lightness (L*) value at 98.55 and lowest b* value at 2.03.
The 48 hr debranched of preheated rice starch at 121 o C was lowest L* value at 85.79
and highest in b* value (7.47).
These was likely due to the higher reducing sugar content in the
24 to 48 hr hydrolysis samples which caused by the condensation of an amino group
and a reducing compound, resulting complex changes in color of RS III samples
(Maillard, 1912).