Effect of added μ-calpain and post-mortem storage on the mechanical properties of bovine single muscle fibres extended to fracture

Effect of inhibition of μ-calpain on the myofibril structure and myofibrillar protein degradation in postmortem ovine muscle

BACKGROUND

Tenderness is considered to be one of the most important attributes of meat quality. Myofibrillar protein degradation contributes to meat tenderization during postmortem ageing. In this process, calpain is the primary enzyme catalyzing the proteolysis. To further understand the action of calpain in meat tenderization, a μ-calpain inhibitor, MDL-28170, was used and its effects on sarcomere structure and myofibrillar protein degradation were determined.

RESULTS

The results of the present study showed that inhibition of μ-calpain significantly reduced muscle myofibrillar fragmentation compared to the group without μ-calpain inhibitor. Meanwhile, the sarcomere structure of the μ-calpain inhibited muscle was only slightly broken and largely remained integral 48 h postmortem. Myosin heavy chain, actin, desmin, troponin T and troponin I were identified to be substrates of μ-calpain by liquid chromatography-tandem mass spectrocopy and western blotting, and were detected with a higher degradation degree in the control group compared to the μ-calpain inhibition group.

CONCLUSION

Comparatively, myosin heavy chain and actin were found to be less sensitive to μ-calpain compared to desmin, troponin T and troponin I. These findings provide a better understanding of the contribution of μ-calpain to the myofibril structure and myofibrillar protein degradation of ovine muscle. © 2016 Society of Chemical Industry.

Meat quality traits as a function of cow maturity

To investigate the physico-chemical and sensory properties of striploin muscles, 90 Hanwoo carcasses (QG 1⁺ ) were randomly selected within six maturity levels (4 to 9 according to age in months). Results demonstrated that the protein contents at maturity levels 4 and 5 were significantly higher than 9. No significant difference in fat, moisture and collagen contents were found at different maturity levels (P > 0.05). The quantity of collagen type I and ratio of type I to III were observed at higher maturity levels; collagen type III showed significantly high levels (P > 0.05) at low maturity and decreased with increase in maturity levels. Warner-Bratzler shear force (WBSF) was significantly lower in groups 4 to 6, whereas water holding capacity (WHC) was significantly higher than maturity level 8 and 9 groups (P < 0.05). There were no significant differences in cooking loss among the maturity level groups (P > 0.05). Color properties, L* values of striploin muscle from maturity level 4 were significantly different from level 9 (P < 0.05). Sensory evaluation at level 4-6 groups had significantly higher tenderness and overall likeness scores than level 9 (P < 0.05). The maturity levels were significantly correlated with age, fat, protein content, WHC, WBSF, cooking loss, CIE L* values and sensory properties like tenderness, juiciness, flavor-likeness and overall likeness.

Anisotropic Compressive Properties of Passive Porcine Muscle Tissue

The body has approximately 434 muscles, which makes up 40–50% of the body by weight. Muscle is hierarchical in nature and organized in progressively larger units encased in connective tissue. Like many soft tissues, muscle has nonlinear visco-elastic behavior, but muscle also has unique characteristics of excitability and contractibility. Mechanical testing of muscle has been done for crash models, pressure sore models, back pain, and other disease models. The majority of previous biomechanical studies on muscle have been associated with tensile properties in the longitudinal direction as this is muscle's primary mode of operation under normal physiological conditions. Injury conditions, particularly high rate injuries, can expose muscle to multiple stress states. Compressive stresses can lead to tissue damage, which may not be reversible. In this study, we evaluate the structure–property relationships of porcine muscle tissue under compression, in both the transverse and longitudinal orientations at 0.1 s−1, 0.01 s−1, or 0.001 s−1. Our results show an initial toe region followed by an increase in stress for muscle in both the longitudinal and transverse directions tested to 50% strain. Strain rate dependency was also observed with the higher strain rates showing significantly more stress at 50% strain. Muscle in the transverse orientation was significantly stiffer than in the longitudinal orientation indicating anisotropy. The mean area of fibers in the longitudinal orientation shows an increasing mean fiber area and a decreasing mean fiber area in the transverse orientation. Data obtained in this study can help provide insight on how muscle injuries are caused, ranging from low energy strains to high rate blast events, and can also be used in developing computational injury models.

Breaking strength of dry fermented sausages and their correlation with texture profile analysis (TPA) and physico-chemical characteristics

In order to assess its usefulness for monitoring textural properties of dry fermented sausages (chorizo, salchichon, salami, fuet and mini-fuet) the determination of breaking strength (BS) was evaluated. Texture profile analysis (TPA) and physico-chemical measurements (pH, aw, dry matter, fat content) were also performed. The BS determined by tensile test and TPA analysis produced complementary information that allowed these meat products to be grouped according to four different textural profiles. These profiles were characterized (p<0.05) by the values of BS, hardness, adhesiveness, cohesiveness and springiness. Multivariate analysis confirmed that BS and TPA parameters were correlated significantly (p<0.00005). On basis of these results, TPA parameters could be used to construct regression models to predict BS and therefore, to obtain a more complete textural property description of the dry fermented sausages. The resulting regression model was BS=-0.777+0.728∗adhesiveness-16881∗cohesiveness+1884.61∗springiness+0.042∗hardness (R(2)=0.634, p<0.00005).