The use of electronic grading probes for the objective assessment of PSE and DFD in pork carcasses

Three electronic grading probes, the Hennessy Grading Probe (GP-II), Fat-O-Meater (FOM) and Destron Pork Grader (PG-100) were assessed for their ability to detect the PSE/DFD conditions in pork. Carcasses were probed either at the time of grading (35, 45 or 60 min post mortem for the GP-II and PG-100, and 60 min post mortem for the FOM) or 24 h post mortem for all three probes. Probings were made between the 3rd and 4th last ribs, 7 cm lateral to the mid-line on the left side of the carcass. The relationship between the mean internal muscle reflectance, calculated by averaging all reflectance values less those recorded for the first and last 4 mm of muscle thickness, and the overall quality of boneless loins was used to assess the three probes. The overall quality of the boneless loins was subjectively assessed 24 h post mortem using a 5-point descriptive scale for paleness and structure in use in Canada since 1984 to describe the PSE/DFD conditions in pork. The relationships between the mean internal muscle reflectance and the subjectively determined overall quality score were weakest at time of grading and strongest at 24h post mortem. The coefficients of correlation were as follows: at 35 min post mortem, GP-II: -0·23 and -0·23 for paleness and structure, respectively, PG-100: -0·01 and -0·24; at 45 min post mortem, GP-II: -0·30 and -0·29, PG-100: -0·01 and -0·22; at 60 min post mortem, GP-II: -0·42 and -0·37, FOM: -0·01 and -0·02, PG-100: -0·29 and -0·30; at 24h post mortem, GP-II: -0·68 and -0·58, FOM: -0·53 and -0·50, PG-100: -0·45 and -0·49. Our results strongly suggest that early post mortem reflectance measurements made with the GP-II, FOM or PG-100 were of no value in detecting the PSE/DFD conditions in pork. Furthermore, despite relatively strong correlations between the mean internal muscle reflectance measured 24 h post mortem and the subjectively determined quality score, the extent of overlapping between quality scores in the distribution of the mean internal muscle reflectance within each quality score precluded the definition of unique reference values for each quality score. Consequently, the measurement of the mean internal muscle reflectance could not reliably distinguish the various Canadian quality standards used to identify PSE/DFD in pork.