Development and Validation of a Probe to Measure Meat Quality

Inconsistent eating quality is one of the major problems faced by the sheep meat industries, as the age, weight, sex and fat scores currently used to determine the value of carcases are poorly related to the traits which indicate eating quality. Raman spectroscopy is one technology which has the potential to be used as a tool for carcase assessment as it is rapid, non-destructive and capable of providing information on the protein and lipids present in meats. Therefore, the aim of this research was to determine the potential of a hand held Raman spectroscopic device to predict meat quality traits of lamb for commercial application. Spectra collected 25 min, 24 h and 5 days post mortem (PM) using a 671nm hand held Raman device were regressed against traditional indicators of meat quality including shear force values, pH values, cooking loss, purge, colour, sarcomere length, particle size, intramuscular fat levels and major fatty acid group concentrations using partial least squares. Furthermore, models to determine relationships between shear force and traditional indicators (likewise pHu and traditional indicators) were fitted using simple linear regression. Overall, predictions of the major fatty acid groups were the most promising, yielding coefficients of determination of (R2) of 0.93 '' 0.54 and reductions in error of up to 7.8% for the prediction of polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids as well as saturated fatty acids which had been adjusted for the level of intramuscular fat (IMF). However, there may be some overlap in Raman signals arising from the head groups of phospholipids, which may be causing a reduction in the accuracy when cross validation is used to determine the robustness of the prediction. Hence, further research needs to determine the impact of various lipid conformations on the prediction of major fatty acid groups in fresh intact muscle. The best prediction of shear force values at 5 days PM was found using spectra collected 24 h (R2cv = 0.27), however the prediction of shear force was inconsistent over time as further experiments demonstrated no ability to predict shear force values. Therefore, this research indicates that prediction of shear force of fresh intact lamb using Raman spectroscopy does not have the repeatability and robustness required by industry. ''Models for the prediction of other meat quality traits suggested that there was also an ability to predict pH24 and purge using spectra measured pre-rigor (R2cv = 0.27 and 0.32) and pHu, purge and L* values from spectra measured at 24 h post mortem (R2cv = 0.22 '' 0.59). As colour, water holding capacity, structure pH decline and pHu are related, it is hypothesised that Raman spectroscopy is able to predict meat quality traits which relate to early PM metabolism. However, since Raman spectra of intact meat are complex, further research is required to determine the impact of spectral overlap from compounds of similar chemical conformation, determine the biochemical processes which contribute to these predictions and validate these findings.