Nuclear Magnetic Resonance for Meat Quality Assessment Program (ie. 3 Sub-projects) [SNGPI.027]

Summary

Magnetic resonance imaging (MRI), nuclear magnetic resonance imaging (NMRI), or magnetic resonance tomography (MRT) is a medical imaging technique used in radiology to investigate the anatomy and physiology of the body in both health and disease. MRI scanners use strong magnetic fields and radiowaves to form images of the body.
More recently, NMR technology has been used to study meat qualityprimarily in research applications.
R&D Activities
Under project P.PSH.0229, low field nuclear magnetic resonance (LF-NMR) investigated the potential to manage quality during processing and predict product performance in the market as well as providing robust data which can be fed back to farmers and used in decision support. There is evidence in the literature that LF-NMR can measure fat levels in meat and changes in water compartments in lean tissue associated with rigor, water binding and cooking. This indicates potential to measure key meat quality attributes using LF-NMR. However, existing LF-NMR bench top units are impracticable for online use in meat plants
Under project P.PSH.0286, a NZ based manufacturer (Magritek) had developed a number of open-topped low-field (LF) NMR prototypes (NMR-MOLE and NMR-MOUSE) that allowed the placement of samples on top of the sensing unit. This enabled the measurement of larger samples than was possible with bench top LF-NMR units and eliminated the need to cut a sample from the product. Although available commercially, it was unclear as to whether the Magritek instruments were capable of measuring meat quality attributes. In addition, it was unclear whether parameters related to diffusion or mobility are the most appropriate to assess meat quality attributes using LF-NMR.
Conducted collaboratively by AgResearch MIRINZ,Murdoch University and Magritek at Magritek, Wellington, New Zealand, the attached reports detailed experiments to investigate the above.
Oneexperiment was to examine the signal from a Halbach NMR instrument and how itcorrelateds to shear force and drip loss. A previous trial on a limited number of samplessuggested that the Halbach NMR instrument could predict shear force during ageing. Thepresent trial was carried out on a larger sample set to verify the encouraging result.
A two-factorial experiment was designed using electrical stimulation and wrapping to create a sample set of lamb loins (n = 40) that varied in meat tenderness. Shear force and drip loss measured day 1 to 4 post slaughter were compared to LF-NMR data.
Relaxation measurements were significantly affected by ageing when the same samplewas measured in the Halbach NMR instrument on day 1 to day 4 post slaughter. The T21 time constant decreased, the T21 population increased and the T22 population decreasedover the ageing period. This indicated an increased concentration of water within theintramyofibrillar space and decreased concentration in the extramyofibrillar spacefacilitated by proteolysis and concomitant swelling of the muscle fibers.
The overall correlation between shear force and NMR relaxation measurements was 0.62explaining 69% of the variation. Models fitted for the four different ageing times resulted inindividual R2 of 0.40 to 0.84. The correlation might be improved if the effect of withinmuscle variability is reduced by using the same sample for both measurements. This ispossible with a one-sided NMR instrument like the Magritek NMR MOLE.
The research indicateds that increasing T21 population (K22) and a decreasing T21 timeconstant is associated with more tender meat. The opposite result has been observed inpork. This result needs to be further confirmed with red meats.
The prediction for drip loss gave a lower value of R2 (0.42 explaining 50% of thevariation). Further work will utilise the centrifuge drip loss method and as a result strongercorrelations are expected.
The correlation between shear force and the NMR relaxation parameters is a positiveresult, providing further evidence to support ongoing research using NMR to predicttenderness online in post rigor meat. Further work with the Halbach and an upgradedone-sided NMR instrument like the Magritek NMR MOLE was recommended to confirm andimprove the correlations.