Quality deterioration mechanism of freeze-thawed sweet potato oat dough: In terms of ice crystals and protein changes.

Sweet potato-oat composite dough is a nutritious, functional dough with promising market potential. This study investigates its quality changes during freeze-thaw cycles from the perspectives of ice crystals and protein alterations to provide theoretical support for its processing and production. After freeze-thaw cycles, both the storage modulus and loss modulus of the dough decrease, resulting in increased hardness, reduced resilience and chewiness, lower sensory scores, decreased specific volume, and darker color. From the perspective of ice crystals, the formation and melting of ice crystals caused significant changes in water status: strongly bound water increased then decreased, weakly bound and free water decreased then increased, and freezable water content rose significantly (p < 0.05). These changes disrupted the dough's structure, leading to pore enlargement and collapse. From the protein perspective, freeze-thaw treatment significantly reduced β-folds and α-helices, causing the protein structure to become loose and disordered, further affecting elasticity and viscosity. Results showed that after more than three freeze-thaw cycles, the dough's processing properties and product quality deteriorated, making it unsuitable for further use. PRACTICAL APPLICATION: Sweet potato oatmeal composite dough is a new type of functional composite dough, which is rich in nutrients and has a promising market prospect. This study reveals the mechanism of the influence of ice crystal formation and protein structure changes on the quality of sweet potato oat dough during freezing, which can provide a reference for the study of frozen dough of other miscellaneous grains. By exploring the changes in dough quality during freezing storage and transport, reasonable freezing storage and transport times and conditions were developed to reduce the effects of freezing and thawing on dough quality, and to ensure the taste and value of the product, thus providing consumers with better frozen pasta choices.