Accurate determination of endpoint temperature of cooked meat after storage by Raman spectroscopy and chemometrics

• Raman spectroscopy was used to predict endpoint temperature (EPT) after chilling.
• The Raman prediction of EPT was independent of storage time (4 or 8 days).
• Raman was useful to classify cooked meat with EPT of below and above 65 °C.
• Raman did not reveal any chemical or structural changes occurring during storage.
• Fluorescence spectroscopy revealed changes in environment of aromatic amino acids.

Control of the endpoint temperature (EPT) of cooked meat products is very critical to ensure that undercooked “ready to eat” products do not reach to the consumers. The objective of this study was to investigate if Raman spectroscopy in combination with multivariate data analysis can be used to determine the EPT in cooked meat after storage. Pork muscle was heat treated at 50 to 80 °C for 2 h and stored for 4 and 8 days at 4 °C under vacuum packaging. The study shows that EPT can be predicted from Raman spectra even after storage time of 8 days (RCV2 = 0.98, RMSECV = 1.68 °C, RMSEP = 1.69 °C). The study further shows that it is possible to classify if the stored samples were cooked to an EPT below or above 65 °C (97.87% and 97.62% of the calibration set and test set were correctly classified, respectively). While Raman spectroscopy is able to elucidate the structural changes in the secondary structure, disulfide bonds and in turn changes in environment of aromatic amino acid residues after heat treatment, it was insensitive to any chemical or structural changes occurring in the cooked meat during storage. Fluorescence spectroscopy was used to support the results from Raman spectroscopy by measuring the changes in environment of the aromatic amino acids in the cooked meat. The results show that Raman spectroscopy has the potential to be used by the processing industry and/or food inspection to ensure that all cooked muscle products have reached the recommended EPT.