Changes in meat quality and muscle fiber characteristics of beef striploin (M. longissimus lumborum ) with different intramuscular fat contents following freeze-thawing

Adipose (fat) tissue has different physical properties from skeletal muscle tissue, and its moisture content is relatively low; thus, freezing or freeze-thawing of meat affects its quality. However, the effect of intramuscular fat (IMF) of meat has not been comprehensively studied. The changes in the meat quality and muscle fiber characteristics of beef striploin (M. longissimus lumborum; LL) with different IMF contents (63.5 g/kg-260.3 g/kg; n = 52) following freeze-thawing were examined. Freeze-thawing destroyed muscle fibers, and the fiber size was decreased irrespective of muscle fiber type or IMF content. However, the size of type I and IIA muscle fibers was largely altered in LL muscles with lower IMF content. Low IMF content increased the tenderness and decreased the pH of LL muscles; the effects of low IMF content on discoloration in LL muscles were less prominent. Larger IMF particles and higher density were associated with reduced thawing loss in LL muscles. IMF content reduced the lightness of frozen-thawed meat, but it did not excessively reduce water-holding capacity and pH. Thus, deterioration in meat quality can be prevented by considering the IMF content during the freezing process.