Mitigating Protein Denaturation of Surimi via Immersion-freezing Using Water-soluble Soybean Polysaccharide(s)
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Abstract:
The effects of water soluble soybean polysaccharide (SSPS) on the freezing efficiency and protein denaturation of surimi were investigated by immersion freezing. The fresh grass carp (Ctenopharyngodon idellus) surimi was used as the raw material. The effect of SSPS addition (1%, 3% and 5%) on the immersion-freezing process of the surimi were firstly studied. Results showed that the characteristic freezing time of the surimi with 3% SSPS was the shortest, and the myofibrillar protein content was the highest after a 14-day frozen storage. Over the 8-week frozen storage, the protein denaturation of surimi was evaluated by measuring the Ca2+-ATPase activity, total sulphydryl content, active sulphydryl content and salt extractable protein content. After 2 weeks of frozen storage, all these four evaluation indices of the treated surimi samples were significantly higher than those of the control surimi, with 3% SSPS providing the greatest cryoprotective effect on protein denaturation. After 8 weeks of frozen storage, the Ca2+-ATPase activity, total sulphydryl content, active sulphydryl content, salt extractable protein content of the myofibrillar protein for the surimi treated with 3% SSPS was 0.35 μmol (pi)/[mg (protein)·min], 3.41×10-5 mol/g protein, 2.37×10-5 mol/g protein, and 41.74 mg/g, respectively, which were increased by 16.87%, 14.94%, 18.10% and 17.35%, respectively, compared to the control surimi. The results indicate that SSPS addition can significantly increase the freezing rate of surimi, mitigate the protein denaturation during frozen storage, thus, SSPS can be used as a low-sweet cryoprotectant for surimi proteins.
