Ultrastructural changes in bovine Longissimus muscle during postmortem ageing

Area of Science:

• Muscle biology
• Meat science
• Postmortem biochemistry

Background:

• Understanding postmortem aging is crucial for meat quality.
• Muscle fiber types (Type 1 and Type 2) exhibit distinct structural characteristics.
• Z-disc integrity and myofibrillar fragmentation are key factors influencing meat texture.

Purpose of the Study:

• To investigate the ultrastructural changes in Type 1 and Type 2 myofibers during postmortem aging.
• To correlate these changes with meat tenderness in young Hereford bulls.

Main Methods:

• Ultrastructural analysis of longissimus muscle samples from young Hereford bulls.
• Examination at three postmortem time points: 1 hour, 48 hours, and 216 hours.
• Microscopic observation of Z-discs and myofibrillar structures.

Main Results:

• Type 1 myofiber Z-discs remained largely unchanged throughout postmortem aging.
• Type 2 myofiber Z-discs showed degradation, increasing from 1 to 48 hours postmortem.
• Myofibrillar fragmentation occurred in both fiber types, particularly at the Z-disc-I-band junction, and was associated with increased tenderness.

Conclusions:

• Postmortem aging affects muscle fiber ultrastructure differently between Type 1 and Type 2 myofibers.
• Z-disc degradation in Type 2 fibers and myofibrillar fragmentation contribute to changes in meat texture.
• Fragmentation at the Z-disc-I-band junction is a significant indicator of meat tenderness.