Electrical Impedance to Easily Discover Undeclared Freeze-thaw Cycles in Slaughtered Bovine Meat.

A H Dell’Osa,G Battacone,G Pulina,F Tocco,A Concu,F Velluzzi,A Fois,A Loviselli

doi:10.2478/joeb-2021-0002

Abstract

A portable electrical impedance spectroscopy device was developed to monitor the bioimpedance resistive component of bovine meat by injecting a sinusoidal current of 1 mA at 65 kHz. Both right and left longissimus dorsi muscles were trimmed from 4 slaughtered cows. The left muscle portions were frozen to −18 °C for 7 days while the right ones were meantime maintained at 5 °C. Mean value of impedance per length (Ω/cm) of frozen and thawed left samples was 31% lower than that of right non-frozen one (P = 0.0001). It was concluded that the device is reliable for monitoring the maturation of beef meat in situ with the possibility of revealing undeclared freeze-thaw cycles.

Highlights

From a structural point of view, the trimmed meat from bovine muscle is an anisotropic tissue, which is characterized by a composite network of muscle fiber bundles containing aligned myofibers surrounded by a fine endomysial envelope of connective tissue
It has been found that during the post-rigor period the behavior of its electrical impedance (Zm) reflects major changes occurring in the meat's structure [1], and these modifications are related to the disruption of the myofibrillar organization of the cytoskeleton and of cell membranes, due to protease activity [2]
To highlight the different behavior of Zm when longissimus dorsi muscles (LDm) were submitted or not to a freezing treatment, Figure 5 shows a graphic representation of a typical behavior of the impedance in the longissimus dorsi muscle samples concerning one of the tested animals

Summary

Introduction

From a structural point of view, the trimmed meat from bovine muscle is an anisotropic tissue, which is characterized by a composite network of muscle fiber bundles containing aligned myofibers surrounded by a fine endomysial envelope of connective tissue. Electrical characteristics of meat are due to frequency-dependent materials, which define its capacitive reactance due to the cell membrane property of maintaining the separation of the negative from positive electrical charges across it, as in an electrical capacitor Both these electrical specificities give rise to an electric anisotropy of the muscle, which is closely dependent on its histological characteristics. It has been found that during the post-rigor period (which begins 2 – 3 days after slaughter) the behavior of its electrical impedance (Zm) reflects major changes occurring in the meat's structure [1], and these modifications are related to the disruption of the myofibrillar organization of the cytoskeleton and of cell membranes, due to protease activity [2] During this time-dependent proteolysis, i.e. the meat's maturation, degradation occurs in proteins with structural tears and myofibril fragmentation, together with degradation in cytoskeleton architecture [3]. These structural modifications of trimmed muscle give rise to a progressive loss of structural anisotropy from which a reduction of Zm occurs [4,5]

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Discussion

Conclusion