Comprehensive evaluation of the changes in the properties of wheat starch at different freezing rates after interaction with inulin based on different polymerization degrees

• Freezing promotes the decomposition and reassembly of starch. • LPI effectively inhibits the recrystallization of amylose. • HPI significantly reduces the recrystallization of amylopectin. • The effects are attributed to the cross-linking, hydration, and permeation properties of inulin. The adverse effects of freezing wheat starch could be mitigated by effective cryoprotectants. In this study, the changes in starch endogenous composition, multiscale structures, and rheological properties were comprehensively evaluated under different freezing rates to investigate the effects of inulin with different degrees of polymerization on wheat starch. The results indicate that rapid freezing has been observed to enhance the short - range order of starch. The addition of inulin weakens the interactions between starch and water molecules during freezing, leading to a reduction in bound water content by up to 22.52%, effectively inhibiting starch retrogradation. This inhibitory effect was manifested in reductions of 5.34% in true density, 23.93% in porosity, 22.08% in particle size, and 62.50% in the proportion of damaged starch. It was also accompanied by a decrease in the structural orderliness of the frozen starch, with the area of microcrystalline regions reduced by 0.57% to 11.26%. Furthermore, inulin reduced the gelatinization temperature of frozen starch and significantly inhibited the recrystallization behavior of starch gels. As a result, the retrogradation viscosity decreased by 11.39% to 43.20%, leading to the formation of a weak gel network structure with controlled thixotropic properties (yield stress τ₀ ranging from 0.794 to 5.564 Pa). Overall, the efficacy of inulin as a cryoprotectant increased with its degree of polymerization. Inulin with a high degree of polymerization appears to directly crosslink with amylopectin chains, whereas inulin with a low degree primarily exerts a pronounced hydration and osmotic effect within starch granules. Correlation analysis further revealed that amylopectin plays a pivotal role in regulating the structure and properties of frozen starch. These findings provide robust scientific evidence for the development of high - quality frozen wheat starch products.