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United States Department of Agriculture

Agricultural Research Service

Title: Technical Note: Comparison of Myofibril Fragmentation Index from Fresh and Frozen Pork and Lamb Longissimus

Authors
item Veiseth, Eva - AGRIC. UNIV. OF NORWAY
item Shackelford, Steven
item Wheeler, Tommy
item Koohmaraie, Mohammad

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2000
Publication Date: N/A

Interpretive Summary: During postmortem storage of cuts of meat or whole carcasses the meat will gradually tenderize. The reason for this tenderization is breakdown of proteins that are responsible for structural integrity of myofibrils. While postmortem tenderization occurs in most carcasses, it does not occur in all carcasses. A method to quantify the extent of postmortem tenderization is called the Myofibril Fragmentation Index (MFI). MFI measures the level of breakdown of the muscle proteins that hold the myofibrils together and it is strongly associated with indices of meat tenderness. MFI is normally determined on fresh muscle. It is not known if MFI can be determined on frozen muscle. For time and other constraints, it would be far easier if MFI could be determined on frozen muscle. Furthermore, measures of tenderness are frequently obtained on frozen and thawed samples. The objective of this experiment was, therefore, to determine if there is a difference between MFI values of fresh and frozen lamb and pork longissimus. MFI was determined on fresh and frozen (23 to 26 days at -70 deg C) longissimus of lamb (n = 24) and pork (n = 12). The differences between fresh and frozen MFI were not significant for either species (P > .05). These results indicate that MFI can be determined on fresh or frozen muscle.

Technical Abstract: Myofibril Fragmentation Index (MFI) is strongly associated with indices of meat tenderness such as Warner-Bratzler shear force and sensory tenderness. MFI is normally determined on fresh muscle. It is not known if MFI can be determined on frozen muscle. The objective of this experiment was, therefore, to determine if there is a difference between MFI values of fresh and frozen lamb and pork longissimus. MFI was determined on fresh and frozen (23 to 26 d at -70 deg C) longissimus of eight lamb carcasses at 1, 3, and 15 d of postmortem storage (n = 24) and on longissimus of 12 pork carcasses at d3 postmortem storage (n = 12). The R**2 between MFI of fresh and frozen muscle was 0.94 and 0.92 for lamb and pork longissimus, respectively. The differences between fresh and frozen MFI were not significant for either species (P > .05). These results indicate that it is not necessary to determine MFI on fresh muscle.

Last Modified: 12/21/2014
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