Enhancing the anti-freezing properties of glucono-δ-lactone induced tofu through the incorporation of curdlan

Abstract

To improve the water retention capacity and texture stability of tofu induced by glucose-δ-lactone (GDL) during frozen storage, the effect of adding polysaccharide was evaluated in this study. The results showed that when 3% curdlan was added, the water retention of tofu frozen at −18 °C for 4 weeks (64.42%) closely resembled that of unfrozen tofu (66.16%). Simultaneously, the texture of the tofu was notably conserved in comparison to the fresh tofu, and the gel network exhibited a persistent density and uniformity. There is a discernible difference between the freezing and thawing onset points of tofu with the incorporation of curdlan gum, and curdlan combines with water to fill in the interstitial spaces and pores of the protein network, which effectively hinders the migration and flow of water. Further infrared studies demonstrated that the hydrogen bonds in the network were strengthened, which contributed to the stability of the tofu structure integrity. Meanwhile, the further cross-linking of protein molecules in the gel network and the formation of rough networks during the freezing process were prevented. This study reveals that curdlan forms a robust, tightly bound association with water, generating an intricate and interwoven network alongside soymilk protein aggregates, empowering the frozen tofu to effectively retain its quality and texture, closely resembling that of the fresh tofu.