The effect of gamma-poly glutamic acid as a cryoprotectant on crayfish physicochemical and texture properties during frozen storage

Because of the potential health risks associated with current cryoprotectants, there is a need for cryoprotectants with a high level of safety. The feasibility of two gamma-polyglutamic acid concentrations (2 and 4%) as cryoprotectants compared to a conventional cryoprotectant mixture of 4% sucrose + 4% sorbitol (S–S) on the quality of cooked crayfish during a 2-month storage period at −20 °C was investigated in this study. Microstructural imaging demonstrated that γ-PGA treatments restrict the formation of ice crystals in muscle fibers, thereby slowing the progression of crayfish muscle fiber damage during storage. When treated with 2% and 4% γ-PGA, the total sulfhydryl and carbonyl contents were 4.45 and 5.14 mol/105 g protein and 3.68 and 3.17 nmol/mg protein, respectively, compared to the control sample, which had 3.94 mol/105 g protein and 4.04 nmol/mg protein at the end of storage. Furthermore, samples treated with 2 and 4% γ-PGA increased their water-holding capacity from 61.54 to 65.14 and 71.64%, respectively, compared to the control sample. This demonstrates the potency and efficiency of the 4% γ-PGA concentration. Our study could provide useful guidelines for using γ-PGA as an effective cryoprotectant rather than sucrose-sorbitol mixtures in frozen crayfish preservation and related products.