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The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
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Cross-bridge Cycle

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Related Experiment Video

Updated: May 27, 2026

Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis

Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis

Published on: December 1, 2023

Calpains from thaw rigor muscle.

¹INRA, Station de Recherches sur la Viande, 63122 St. Genés Champanelle, France.

|November 9, 2011

Summary

Freezing and thawing beef affects calpain activity and meat tenderness. Rapid thawing reduces calpain and yields tender meat, while slower thawing preserves calpain but results in tougher beef.

Area of Science:

Food Science
Meat Science
Biochemistry

Background:

Calpains are calcium-dependent proteases involved in meat tenderization.
Understanding calpain activity during post-mortem processing is crucial for meat quality.

Purpose of the Study:

To investigate the impact of freezing and thawing on calpain activity and meat toughness.
To compare these effects with chilled meat processing.

Main Methods:

Pre-rigor beef muscles (Longissimus lumborum and diaphragma) were frozen at -70°C.
Thawing occurred at various temperatures, and calpain activity and meat toughness were measured.
Meat was also cooked from a frozen state and stored at -3°C for different durations.

Main Results:

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Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis

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Fluorescence-based Measurement of Store-operated Calcium Entry in Live Cells: from Cultured Cancer Cell to Skeletal Muscle Fiber

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Freezing did not affect initial calpain activity, but thawing reduced it.
Rapid thawing (30°C for 20 min) significantly decreased μ-calpain activity (to 14%) and resulted in tender meat when cooked from frozen.
Storage at -3°C prevented thaw-shortening but led to tougher meat with reduced μ-calpain activity (to 70%), with further storage decreasing both toughness and μ-calpain.

Conclusions:

Calpain activity, particularly μ-calpain, plays a significant role in meat toughness variation during thaw rigor.
Thaw-induced changes in calpain activity are comparable to those during rigor mortis development and aging.
Meat tenderness is more closely linked to calpain activity than sarcomere length in thaw rigor conditions.