Molecular, crystal and physicochemical properties of granular waxy corn starch after repeated freeze-thaw cycles at different freezing temperatures.

The study was undertaken to reveal the effects of freeze-thaw cycles at different freeze temperature (−20 °C, −40 °C and −80 °C) and the number of freeze-thaw cycles (3, 6, 12, 18, 24 times) on physicochemical and structural properties of waxy corn starch. The number of pores on the surface of starch granules increased, but there was no significant (P < 0.05) effect on molecular weight, transparency, freeze-thaw stability and the crystal structure of starch after repeated freeze-thaw cycle. But the crystallinity intensity decreased after freeze-thaw cycles treatment and a tiny decrease in onset, peak, conclusion temperature and gelatinization enthalpy were found. The RVA analysis exhibited an increase in gelatinization temperatures and a decrease in breakdown and setback value after freeze-thaw treatment, which manifested an increase in the aging and heat resistance of waxy corn starch paste. However, there was no statistical (P < 0.05) difference between different freeze temperatures at the same number of freeze-thaw cycle on physicochemical and structural properties of starch. The obtained data could be helpful in evaluation of the repeated freeze-thaw treatment of waxy corn starch-based foodstuffs and providing the theoretical basic for revealing the effect of repeated freeze-thaw processes in manufacture applications.