Meat color evaluation and pigment levels in bullfrog (Rana catesbeiana) slaughtered by different methods

This work aimed to evaluate the muscle color and heme pigment content of bullfrog muscles after electrical or thermal stunning and use or not of bleeding. Stunning method did not influence (P>0.05) the instrumental color or the total heme pigment content of the meat or the relative chemical forms of heme pigments. However, muscle myoglobin content was lower in electrically stunned frogs (P<0.05). Overall, the myoglobin content of bullfrog meat was similar to that of avian white muscles. Bleeding enhanced the final quality of the meat. Meat from bled animals was whiter and had an important contribution of the b* value (yellowness) to its color. Muscle hemoglobin content of bled frogs was lower (P<0.05) than that of un-bled frogs, and negatively correlated (P<0.05) with slaughter weight. Oxymyoglobin, reduced myoglobin, and metmyoglobin contents were, respectively, highly correlated with lightness (L*), redness (a*), and yellowness (b*).