Ultrasound-Assisted Enzymatic Deamidation Treatment for Developing Soft Surimi Gel for Dysphagia: Gel Properties, In Vitro Digestibility, and Protein Mechanisms

An urgent necessity exists to create foods that cater to the requirements of patients with dysphagia. The softened surimi gel appropriate for dysphagia patients was produced through ultrasonic-assisted Protein-glutaminase (PG) deamidation treatment. In comparison to the control group, the hardness and gel strength of softened surimi gel with a 0.2% PG addition diminished from 607.40 g and 530.79 g mm to 244.60 g and 78.61 g mm, respectively, satisfying the IDDSI Level 5 classification criteria (p < 0.05). The incorporation of PG transformed free water in the fish paste gel into less mobile water, markedly improving the gel’s water holding capacity. The ultrasound-assisted enzymatic deamidation treatment made the surimi gel produce more small molecular peptides and free amino acids during digestion. This treatment diminished hydrophobic interactions in myofibrillar protein gel, augmented hydrogen bonding, elevated the α-helix structure to 46.27%, and decreased the β-sheet structure to 19.18%, with significant differences compared to the control group (p < 0.05). The polarity of the tryptophan residue microenvironment alters and impeding the further folding of unfolded protein structures during heat-induced gelation. This study offers a fundamental theoretical framework for the development of specialized foods that possess safe swallowing and nutritional attributes.