Measurement of the pH value in pork meat early postmortem by Raman spectroscopy
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The pH of a muscle is an accepted parameter to identify normal and deviating meat qualities. In this work, Raman spectroscopy is shown to be suitable for the non-invasive measurement of the early postmortem pH of meat. Raman spectra of ten pork semimembranosus muscles were recorded with a portable handheld device 0.5–24 h postmortem. The spectra were correlated with pH and lactate kinetics measured in parallel. Seven of the muscles were normal, two exhibited accelerated glycolysis and one showed absence of acidification. The pH decline with time could be calculated from the Raman spectra with the Henderson–Hasselbalch equation using only two signals of phosphate vibrations at 980 and 1,080 cm−1 with a close correlation for each muscle, but larger variations between animals. More robust and better correlations for all muscles were obtained with a linear model based on 11 signals from lactate, lactic acid, phosphate, a carbonyl band and nucleotides resulting in R 2 = 0.78 and RMSECV = 0.2 or a partial least-square model using the complete spectrum (R 2 = 0.94 and RMSECV = 0.2). These results show the potential of Raman spectroscopy for an online detection of the pH and thus meat qualities during meat processing.
KeywordsRaman Spectrum Partial Less Square Regression Meat Quality Partial Less Square Regression Model Pork Meat
This work was funded by the German research foundation DFG (Deutsche Forschungsgemeinschaft) in the framework of the cluster project “Minimal Processing” of the Research Association of the German Food Industry (FEI). Financial support for the Research Centre of Food Quality by the European Regional Development Fund (ERDF) is gratefully acknowledged. The authors wish to thank Dr. Heinz-Detlef Kronfeldt for generous support with the prototype handheld Raman device, Dirk Grühn for the excellent cooperation and for providing the pork samples as well as Stefanie Hofmann and Thomas Kador for assistance with lactate and Raman measurements.
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