Application of seaweed polysaccharides in pre-baked frozen bread and their effect on frozen gluten

During the freezing process, the formation and recrystallization of ice crystals can disrupt the gluten structure. This study first investigated the effects of five types of seaweed polysaccharides—sodium alginate, propylene glycol alginate (PGA), κ-carrageenan, ι-carrageenan, and λ-carrageenan on the quality of pre-baked frozen bread. The results showed that seaweed polysaccharides significantly reduced the hardness of pre-baked frozen bread, and PGA significantly increased the bread's volume (P < 0.05). Additionally, the effects of the five seaweed polysaccharides on the physicochemical and structural properties of gluten protein before and after freeze-thaw treatment were investigated. After freeze-thaw treatment, compared with the control group, seaweed polysaccharides increased the proportion of strongly bound water in gluten, reduced the content of weakly bound water, decreased the free sulfhydryl content and surface hydrophobicity index of gluten, and increased the content of α-helix structures. Compared with the other four seaweed polysaccharides, gluten treated with PGA exhibited improved integrity of the gluten network after freeze-thaw treatment. Our results demonstrate the feasibility of employing seaweed polysaccharides as natural cryoprotectants in frozen bakery production.