were ground with a blender and then passed through a 63 lm
screen. The slurry was allowed to stand at 4 C for 48 h. The supernatant
was removed, and the starch cake was re-suspended in 0.4%
sodium hydroxide solution and kept at 4 C for 48 h. The supernatant
was decanted and the starch layer was re-slurried with water.
The starch slurry was passed through a 63 lm sieve and placed at
4 C for 24 h. The steps of washing with water were repeated three
times. The starch cake was re-suspended in water, neutralized with
1 M hydrochloric acid to pH 7, and stored at 4 C for 24 h. The
supernatant was decanted, and the neutralized starch was re-suspended
in water and placed at 4 C for 24 h. Finally, the supernatant
was removed, and the starch cake was dried in an oven at
40 C for 24 h.
Normal and waxy corn starches were isolated using a method of
Sandhu et al. (2004) with slight modifications. Corn kernels were
steeped in water containing 0.16% sodium hydrogen sulphite at
50 C for 24 h. The steeped water was drained off and the corn
grains were ground in a blender. The ground slurry was screened
through a 106 lm sieve. The slurry was allowed to stand at 4 C
for 24 h. The cloudy supernatant was removed and the sediment
was re-slurried in 0.2% sodium hydroxide solution at 4 C for
24 h. The supernatant was discarded and the starch cake was resuspended
in water. The starch slurry was then passed through a
63 lm sieve. The leftover material was discarded and the filtrate
was kept at 4 C for 24 h. The starch was given repeated washings
with water until the pH of starch slurry reached 7. The starch cake
was then dried in an oven at 40 C for 24 h.
Normal potato starch was isolated according to a procedure
described by Puncha-arnon et al. (2007), but with slight modifications.
Approximately 1 cm3 of peeled potato in water were ground
in a blender. The slurry was screened through a bolting cloth, and
the suspension obtained was filtered through a 106 lm sieve. The
filtrate was allowed to settle until a dense, firm starch layer was
deposited. The supernatant was decanted, and the starch cake
was rewashed at least three times. The starch cake was then dried
in an oven at 40 C for 24 h.