Structural and functional properties of wheat starch affected by multiple freezing/thawing cycles

The role of starch in frozen dough was investigated by freezing and thawing wheat starch suspension for 3, 7, and 10 cycles. Freezing caused an increasing damaged starch and leaching materials, as well as the morphological changes of the starch granules. After 10 cycles of freezing and thawing, the relative crystallinity and short-range order increased by 4.3% and 0.251, respectively. These changes resulted in a substantial increase in the gelatinization temperatures, melting enthalpy, and pasting viscosities. Freezing/thawing-treated starch (FTS) showed high susceptibility to enzyme hydrolysis while the resistant starch content of 10 FTS decreased by 28%. Compared with the native starch, an apparent decrease was observed in the specific volume of 86% substitution of bread with FTS while the crumb firmness significantly increased (p > 0.05). Our results showed that freezing could significantly alter the structural and functional properties of wheat starch, thus facilitating irreversible structural transformations from dough to bread.