The slowly digestible properties of high hydrostatic pressure (HHP)-gelatinized non-waxy and waxy rice
starches during the retrogradation were evaluated in this study. The results show that slowly digestible
starch (SDS) was observed at a higher percentage in HHP-gelatinized, non-waxy and waxy rice starches
than in heat-gelatinized starches, after retrogradation for 7 days. The HHP treatment significantly
reduced the enthalpy change of starch retrogradation and retarded the freezable water transformation
into unfreezable water during retrogradation. This indicated that the SDS percentage was not positively
correlated to the retrogradation degree of starch. Furthermore, X-ray diffraction (XRD) data revealed that
the HHP treatment decreased the perfect crystallites of the 7 day-retrograded. Non-waxy and waxy
starches from 19.5% to 12.1% and 15.7% to 11.4%, while increased imperfect crystallites from 26.4% to
30.7% and 28.6% to 31.3%, respectively. These findings suggest that the higher SDS percentage can be
attributed to the formation of less perfect crystallites and more imperfect crystallites during the HHP
and retrogradation treatments.