Frozen samples were stored for 0e14 days in order to analyze
starch retrogradation during chill storage at 4 C. Retrogradation
properties were studied by analyzing the melting endotherm of
recrystallized amylopectin by DSC and results were shown in Figs. 2
and 3. There were no significant differences in onset, peak and
conclusion temperatures for different rates at the same storage
time except with freezing rate of 0.09 C/min (P> 0.05). The mean
melting onset, peak and conclusion temperatures of frozen cooked
rice decreased within 3 days storage (P 0.05).
However, the value of onset, peak and conclusion temperature of
cooked rice frozen with 0.09 C/min were lower than other freezing
rates (0.26, 0.33, 0.53 and 1.45 C/min, respectively) within 3 days
of storage, there were not significant differences of all freezing rates
during the last 11 days of storage. These results indicated that the
onset, peak and conclusion temperatures were not significantly
affected by freezing rates except the rate of 0.09 C/min. However,
the onset, peak and conclusion temperatures of cooked rice were
higher than the results of Yu et al. (2009) without freezing. An
explanation is that the differences may be caused by rice varieties,
or by the freezing process which formed ice crystals in frozen
cooked rice, possibly leading to the damage of the gel structure of
cooked rice grains when thawing at 4 C, thus resulting in the
onset, peak and conclusion temperature differences between
freezing and cooling cooked rice.