Rice Bran Hydrolysates Minimize Freeze-Denaturation of Washed Fish Mince during Extended Freeze-Thaw Cycles

Abstract

ABSTRACT Rice bran hydrolysate (RBH) was produced from hexane-defatted rice bran using subcritical alkaline water followed by enzymatic hydrolysis (Protease G6 at 2% for 6 hr). The RBH was added to Pacific whiting washed mince. The physicochemical and rheological properties of the mince with and without RBH or commercial cryoprotectants (sucrose-sorbitol (S/S)) were evaluated after 0, 7, and 14 freeze-thaw (FT) cycles. The protein solubility and total sulfhydryl group content of all samples decreased as the number of FT cycles increased, while surface hydrophobicity increased. Samples prepared with 2% RBH mixed with 4% S/S (RBH+S/S) and 2% RBH exhibited higher total sulfhydryl group content and protein solubility than 8% S/S and a control. Samples prepared with RBH+S/S and 2% RBH exhibited lower surface hydrophobicity than control but slightly higher than 8% S/S sample. The elastic modulus (G′) of samples prepared with RBH and S/S was higher than that of the control. After gelation was completed, the sample with RBH+S/S showed the highest G′. RBH showed a significant ability to maintain the quality of frozen fish proteins, especially when blended with S/S. This study suggests RBH can effectively protect fish myofibrillar proteins from denaturation during frozen storage and further contribute to reducing sugar/sorbitol.