Novel method for determination of myofibril fragmentation post-mortem
Introduction
Measurement of myofibril fragmentation is one of the most used methods to determine post-mortem proteolysis in meat and has been widely used in studies on beef, pork, chicken and lamb (Olson et al., 1976, Therkildsen et al., 2002, Watanabe et al., 1996, Yu et al., 2005). Several different methods have been developed to measure the myofibril fragmentation in muscle. All the methods involve homogenization of the muscle followed by different techniques to determine the size of the resulting myofibril fragments. The first method developed to measure myofibril fragmentation examined the myofibrils by microscopy (Takahashi, Fukazawa, & Yasui, 1967). The myofibril fragmentation was calculated as the percentage of myofibrils that contained more than four sarcomeres, relative to the total number of myofibrils. Another method determined the size of the myofibril fragments by stirring the myofibrils through filters of specific pore sizes (Davis, Dutson, Smith, & Carpenter, 1980). The weight of the myofibrils remaining on the filters was then used to calculate the myofibril fragmentation. The most used method is based on the turbidity of the myofibrils adjusted to a common protein concentration (Davey & Gilbert, 1968). The turbidity is determined by measuring the absorption at 540 nm of the myofibril suspension. Sometimes the measured absorbance is multiplied by a constant and termed myofibril fragmentation index (MFI) (Olson et al., 1976). Different studies have been made to optimize the turbidity method such as looking at the impact of the homogenizer type and speed (Hopkins et al., 2000, Hopkins et al., 2004, Veiseth et al., 2001). However, the method is time-consuming as the preparation includes two centrifugation steps and subsequent determination of the protein concentration for each sample. The objective of the present study was to estimate myofibril fragmentation by a new method that uses multi angle light scattering from which particle sizes of myofibril fragments can be obtained. The method requires no prior information about the protein concentration of the sample.
Section snippets
Muscle samples
Pig longissimus dorsi (LD) muscles, used to test the efficiency of the Mastersizer to measure myofibril fragmentation during storage were obtained from a commercial slaughterhouse 24 h post-mortem. Half of the LD muscle was immediately frozen in liquid nitrogen and stored at −80 °C and the rest of the LD muscle were aged at 4 °C until day 8 post-mortem and then frozen as above.
Muscle samples used to test the correlation between myofibril fragmentation and Warner–Bratzler shear force (WBSF) were
Results and discussion
To test the potential of multi angle light scattering for direct size estimation of myofibrils and thereby to investigate the possibility of the development of myofibril fragmentation post-mortem, pig muscles stored either one day or eight days were studied. Multi angle light scattering may be used to measure the scattered light from particles in solution. The data from a range of detectors at different angles is used to calculate the distribution of particle sizes in the solution.
Conclusion
The results show that multi angle light scattering is a useful method to determine myofibril fragmentation. A major advantages of multi angle light scattering with respect to determination of myofibril fragmentation is a simple sample preparation that does not require purification of myofibrils in contrast to the traditional turbidity measurement protocol that contains two centrifugation and one filtration steps. Meat samples were studied during storage and changes in myofibril particle sizes
Acknowledgements
The technical assistance of Ahmad Abdalkader Kabel, Marie Sørensen and Marlene Madum Sørensen is gratefully acknowledged. Support for the work was provided by the Danish Ministry of Food, Agricultural and Fisheries and the Danish Meat Association.
References (14)
- et al.
A research note on factors affecting the determination of myofibrillar fragmentation
Meat Science
(2000) - et al.
The impact of homogenizer type and speed on the determination of myofibrillar fragmentation
Meat Science
(2004) - et al.
The effects of the ultimate pH of meat on tenderness changes during ageing
Meat Science
(1996) - et al.
Effects of breed, feed level and conditioning time on the tenderness of pork
Meat Science
(1996) - et al.
Effects of thawing temperature on the physicochemical properties of pre-rigor frozen chicken breast and leg muscles
Meat Science
(2005) - et al.
Relationship of myofibril fragmentation index to certain chemical, physical and sensory characteristics of bovine longissimus muscle
Journal of Food Science
(1978) - et al.
Studies in meat tenderness. 6. Nature of myofibrillar proteins extracted from meat during aging
Journal of Food Science
(1968)