In vitro proteolysis mirrors intact muscle maturation in beef carcasses

Area of Science:

• Meat science
• Biochemistry
• Food science

Background:

• Postmortem beef maturation involves complex biochemical changes influencing meat tenderness.
• Understanding endogenous protease activity is crucial for optimizing beef aging processes.

Purpose of the Study:

• To develop and validate an in vitro assay for studying beef postmortem protease activity.
• To assess the temporal changes in protease activity in different beef muscles during aging.

Main Methods:

• Purified myofibrils from semitendinosus muscle were used as substrates in an in vitro proteolysis assay.
• Samples from longissimus thoracis et lumborum (LTL) and extensor carpi radialis (ER) muscles were analyzed at various postmortem time points (0-14 days).
• Degradation of desmin and troponin-T was quantified over incubation periods, with and without protease inhibitors (EGTA, calpastatin).

Main Results:

• Protease activity was minimal in both LTL and ER muscles at 0 and 1 day postmortem.
• Significant degradation of myofibrillar proteins was observed in LTL muscle from 2 days onward, indicating increased proteolytic capacity.
• Proteolysis was inhibited by EGTA and calpastatin, suggesting the involvement of calpain proteases.
• In vitro degradation patterns mirrored in vivo changes in muscle maturation.

Conclusions:

• Active protease activity in beef muscle is minimal before 48 hours postmortem, especially in LTL.
• The developed in vitro assay using purified myofibrils is a viable tool for studying postmortem proteolysis and beef tenderization.
• This assay can help understand temporal changes in protease activity across different beef muscles during aging.