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Title:Quantification of variation in pork quality and composition traits
Author(s):Arkfeld, Emily Katherine
Director of Research:Boler, Dustin D
Doctoral Committee Chair(s):Boler, Dustin D
Doctoral Committee Member(s):Dilger, Anna C; McKeith, Floyd K; Ellis, Michael; Shackelford, Steven D
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Pork quality
Variation
Abstract:Improving consistency in the U.S. pork supply has long been a goal of producers and processors, though factors contributing to variation in pork composition and quality are ill-defined. Therefore, variation in pork quality and composition and correlations among compositional and quality traits were characterized in multiple studies. In boneless loins destined for export to a quality focused market (N = 154), subjective color and marbling scores at 1 and 28 d postmortem were not correlated with sensory tenderness (P ≥ 0.47), chewiness (P ≥ 0.18), juiciness (P ≥ 0.43), or off-flavor (P ≥ 0.07). Loin firmness measures, collected at a commercial processing facility, did not account for variability in sensory characteristics (P ≥ 0.08). In a larger study, 7,684 pigs were used to characterize the relationship between fresh loin quality with fresh belly quality and fresh and cured ham quality. Ultimate loin pH was correlated with dimensional belly characteristics (r ≥ |0.07|; P < 0.0001) fresh ham instrumental color (r ≥ |0.03|; P ≤ 0.05), and semimembranosus ultimate pH (r = 0.33; P < 0.0001). Instrumental L*on the ventral surface of the loin was related to L* on both of the evaluated muscles of the ham face (r ≤ 0.33; P ≤ 0.0001). Even though significant relationships among the loin, belly, and ham were detected, the variability in belly and ham quality explained by variability in loin quality was poor (≤ 22.1%). Differences in temperature declines during chilling between the loin and ham likely contributed to the weak nature of relationships. Equilibration of longissimus dorsi temperature to ambient temperature occurred at 14 h postmortem (P = 0.0005), yet the semimembranosus had not equilibrated with ambient (equilibration bay) temperature (P < 0.0001) at 22 h postmortem. Using loin quality to draw conclusions about fresh belly and fresh and cured ham quality may be misleading. Pigs of the same dataset were also used to characterize the factors and production practices that contribute to variation in pork composition and quality. The mivque0 option of VARCOMP procedure in SAS was used to evaluate the proportion of variation each independent variable (season, production focus, marketing group, sex, and random variation due to pig and other factors not controlled in this study) contributed to total variance. Random variation including inherent biological differences, as well as factors not controlled in this study, contributed the greatest proportion to total variation for each carcass composition and quality trait. Pig and other factors contributed to 93.5% of the variation in HCW, and marketing group, sex, season, and production focus accounted for 4.1%, 1.4%, 0.8%, and 0.3%, respectively. Variation in percent carcass lean was attributed to production focus (36.4%), sex (15.8%), and season (10.2%). Ultimate pH variation was attributed to pig (88.5%), season (6.2%), production focus (2.4%), marketing group (2.2%), and sex (0.7%). Use of marketing groups by producers to control variation in final BW is also effective in controlling variation in pork quality and primal weights. Variation in carcass quality and composition could be accounted for by independent variables evaluated in this study, but the greatest percentage of variation was due to factors not accounted for in normal marketing practices. Finally, hams from the 7,684 pigs were used to 1) to characterize the effect of marketing group on fresh and cured ham quality, and 2) to determine which fresh ham traits correlated to cured ham quality traits. Leg primal weight and instrumental color were measured on 100% of the population. On the select 10% of the population, hams were fabricated into sub-primal pieces, and three-piece hams were manufactured to evaluate cured ham quality and yield. Data were analyzed as a split-plot design in the MIXED procedure of SAS . Pearson correlation coefficients between fresh and cured ham traits were computed. There were no differences (P ≥ 0.15) in instrumental color or ultimate pH (P ≥ 0.14) among fresh ham muscles from any marketing group. The only exception was the semimembranosus of marketing group 2 was lighter than marketing group 1 (P = 0.03) and the dark portion of the semitendinosus muscle from group 1 was lighter than from group 3 (P = 0.01). Cured lightness values of hams from marketing group 1 and 2 were 1.52 units lighter than hams from marketing group 3 (P ≤ 0.01). Fresh ham quality was not strongly related to cured ham quality. Some correlations were present between fresh and cured ham traits, but those relationships were likely not strong enough to be used as a sorting tool for fresh hams to generate high quality cured hams. Overall, some variability in pork quality and composition can be attributed to management practices of pigs, but the overwhelming contributor to variability was pig and other factors not controlled for in this study. Variability in firmness did not explain significant proportions of variability in pork sensory characteristics. Further, marketing group has little impact on pork quality. Finally, using loin quality as an indicator of whole carcass quality may be misleading. Therefore, in order to determine quality, pork primals must be evaluated independently.
Issue Date:2016-08-11
Type:Thesis
URI:http://hdl.handle.net/2142/95448
Rights Information:Copyright 2016 Emily Arkfeld
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12


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