Starch retrogradation properties of cooked rice were analyzed
by a Perkin Elmer pyris 6 differential scanning calorimeter (DSC)
(Perkin Elmer, USA). The DSC was calibrated with indium (melting
point¼156.6 C, DHf ¼28.6 J/g) and an empty pan was used as
a reference. The cooked rice samples were prepared using the
methods of . After textural properties determination, the
samples of cooked rice was mixed with 99% ethanol (1:4, v/v) and
dehydrated for 12 h. Then the mixture was passed through
a Büchner funnel, and dried at 37 C in an air oven for 24 h. The
dried cooked rice was passed through a 100-mesh (0.147 mm)
sieve after milling by a universal high-speed smashing machine
(FW80-1, Tianjin Taisite Instrument Co. Ltd, China). A total weight
of 4.0 mg cooked rice samples (dry basis) and distilled water (1:2,
w/w) was placed in pre-weighed aluminum sample pans (PE0219-
0062). The pans were sealed hermetically to prevent moisture loss
and kept overnight. For all DSC runs, a sealed empty aluminum
pan was used as reference. The sample was held isothermally at
20 C for 1 min before being heated from 20 to 140 C at 10C/
min. The peak temperature and the enthalpy (DHr, J/g) associated
with the retrograded starch melting peak appearing between 40
and 70 C were calculated. The DHr is used to indicate the enthalpy
of amylopectin starch retrogradation. The DSC measurements
were performed in triplicate. The results were presented as mean
values.