Date Full Report Received
Date Abstract Report Received
Predicting and improving quality is an important goal for the pork industry. The adoption of a U.S. pork quality grading system has been proposed as a potential strategy, of considerable interest, to improving pork quality. However, there are a number of considerations that must be taken into account for such a quality grading system to have clear value to the industry. While factors like the evaluation of quality attributes on-line have been addressed, what is less understood is the association between quality attributes measured at the time of grading and quality traits observed by the consumer after 10-28 d of storage. Therefore, the objective of this work was to determine those relationships using meta-analysis techniques. By performing a meta-analysis, data from several studies can be combined to provide more statistical power. According to Hunter and Schmidt (1990) a meta-analysis is a review of the literature, both published and unpublished, based on a structured statistical approach. Therefore, all available data were considered as candidates for inclusion. The following inclusion criteria were established for studies to provide the most industry-applicable conclusions. First, all studies included must have slaughtered pigs in commercial facilities. Second, studies must have measured loin quality traits on the ventral surface of the loins on day 1 postmortem. Third, quality measurements must have been collected on the same loins again after an aging period that ranged from 12 to 28 days. Original experimental objectives were not taken into account and often times multiple treatments (e.g. dietary, genotype, or slaughter day) were represented within a data set.
Ultimately, eleven independent experiments including a total of 3,957 loins were selected for inclusion in the analysis. First, correlations were determined between fresh pork loin quality attributes evaluated at the packer level (1d postmortem) with those at evaluated after aging for 12 to 28d. Early postmortem color was moderately, not strongly, correlated with aged ventral color and aged chop face color. But no early postmortem color traits were moderately or strongly correlated with measures of eating experience (instrumental tenderness, cook loss, sensory tenderness, juiciness, or flavor). Next, early and aged quality traits were compared within loins to determine the magnitudes of changes in the traits that occur with aging. Instrumental measures of color indicated that loins became lighter, redder, and more yellow during aging. Visual color also changed during the aging period, but the magnitude of the change was only 0.21 units. A
change of only 0.21 units likely means the average consumer would not be able to detect the difference in visual color between early and aged loins. Finally, using a holo-analysis, regression equations were constructed to predict sensory traits from early postmortem quality measures. Early postmortem quality measurements were only marginally predictive of eating quality on pork loin chops. The regression model including extractable lipid, pH and firmness explained only 13% of the variability in sensory evaluations of tenderness. Early postmortem quality traits could predict 28% of the variability in flavor.
Results of this study indicate that early postmortem quality traits are related to those same traits measured after aging. However, those traits are not perfectly correlated. Therefore, it is possible that a loin designated “high quality” based on color observations at the time of quality evaluation in the plant may not necessarily appear “high quality” to a consumer. Furthermore, early postmortem quality traits like color, marbling, pH and firmness, even when combined, offered limited predictive ability for eating quality traits like tenderness, juiciness and flavor. However, it should be noted that eating quality in the studies used for this analysis was from trained sensory panels and therefore, thresholds of acceptability to consumers cannot be established from these data. Further work is needed to validate the usefulness of early postmortem quality traits measured on the ventral surface of loins as predictors of consumer perceptions of eating quality of pork loins.