Guar gum mitigates freeze-thaw damage in wheat starch through multi-scale structural preservation and improves Chinese steamed bread quality.

Repeated freeze-thaw cycles cause multi-scale starch damage in frozen dough and impair product quality. This study evaluated the protective effects of guar gum (0%-1.2%) on starch structures and steamed bread quality under freeze-thaw stress. Doughs containing 0.6% guar gum exhibited the highest storage modulus and loss modulus across all freeze-thaw cycles. After eight cycles, compared with the freeze-thawed control, 0.6% guar gum restored dough viscoelasticity, mitigated the loss of relative crystallinity (from 10.25% to 14.03%), and preserved short-range molecular order. It also increased gelatinization enthalpy (from 8.75 to 9.71 J/g) and suppressed starch retrogradation. 0.6% guar gum reduced bread hardness (from 3046.17 to 2013.07 N), increased specific volume (1.41 cm3/g), and raised rapidly digestible starch content (41.74% vs. 38.35%). Thus, 0.6% guar gum provides balanced multi-scale protection, improving both physical quality and starch digestibility characteristics of frozen steamed bread. This work offers practical guidance for frozen staple food production.