Measuring Myofibril Fragmentation Index

Myofibril fragmentation index (MFI) of the meat samples was measured using the procedure reported in [37 (link)] as an indirect measure of calpain activity. Briefly, 4 g of scissor-minced muscles, free of visible connective tissue and external fat, were homogenized for 30 s in a blender containing 40 mL of cold MFI buffer (2 °C). After many washes, the absorbance of the resultant 0.5 mg/mL solution was measured at 540 nm with a spectrophotometer (HACH DR/3000 Spectrophotometer, (Hach, Loveland, CO, USA). The MFI of each sample was computed by multiplying the absorbance at 540 nm by 200.