Optical measurements of pH in meat

The pH changes occurring in a carcass during the first 24 h after slaughter are important for the quality of the final meat or meat products. Protein denaturation will occur if pH falls to too low a level or if a relatively low pH sets in at a time after slaughter where the carcass temperature is still high. This will result in meat with poor water holding capacity and in extreme cases in meat that is PSE. pH is measured electrochemically using either glass or solid state (IS-FET) electrodes. However, electrochemically based methods are slow to use and do not offer good precision on unhomogenized meat. In this work it has been investigated whether pH can be measured spectroscopically in reflectance using the visual and near infrared spectral regions. On a limited number of pig meat samples (46 longissimus dorsi and 46 semimembranosus muscles) correlations of 0.85 have been achieved using the fast spectroscopic techniques opposed to glass electrode measurements done in duplicate. The prediction errors for the spectroscopic techniques are found to be comparable to the precision of the reference method.