Effect of stunning methods on the differentiation of frozen-thawed bullfrog meat based on the assay of β-hydroxyacyl-CoA-dehydrogenase

Abstract

The effect of electrical or thermal stunning was investigated by β-hydroxyacyl-CoA-dehydrogenase (HADH) assay after extraction in phosphate buffer to segregate unfrozen (stored in crushed ice) from frozen-thawed bullfrog ( Rana catesbeiana) gastrocnemius muscles. Also investigated were possible influences of the type and time of storage on the upper and lower limits of the HADH assay. Stunning method and time of storage in crushed ice did not affect ( P>0.05) the HADH activity in unfrozen or frozen-thawed muscles. However, HADH values of the frozen (−18 °C) samples increased ( P>0.05) over the evaluated period. Nevertheless, it was possible to establish upper and lower HADH values leading to the differentiation of unfrozen from frozen-thawed samples. Samples with HADH values lower than 65 were classified as unfrozen and those with HADH values higher than 69 were classified as frozen-thawed. Samples with HADH values between 65 and 69 were considered as uncertain. Using these limits, a high level of success (96.5%) was attained in distinguishing unfrozen from frozen-thawed bullfrog meat.