The effect of gamma-poly glutamic acid as a cryoprotectant on crayfish physicochemical and texture properties during frozen storage
Taher Abdelnaby, Zhaojie Li, Wanxiu Cao, Changhu Xue
Abstract
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.