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Title:Characterizing the relationship between early postmortem pork loin quality attributes and 14 day aged loin quality attributes and sensory characteristics
Author(s):Klehm, Brandon Joseph
Advisor(s):Boler, Dustin D.
Contributor(s):Dilger, Anna; McKeith, Floyd
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):aged
correlation
early
pork
quality
Abstract:Consumer’s routinely use fresh pork color and marbling as indicators of a desirable pork loin chop, which may explain the decision to use these traits to sort loins for previous proposed grading systems. However, to effectively use these traits to determine pork loin quality, it is crucial to first evaluate their repeated capability of predicting a satisfactory eating experience. Also, the relationship between early postmortem quality traits and aged quality traits of pork loins stored under various conditions must be established. Therefore, the objective of this work was to determine the relationship between early and aged postmortem pork loin quality traits, compare aged pork quality of vacuum-packaged intact loins and case-ready packaged chops, and to determine the interactions between quality grade, packaging type, and degree of doneness on sensory traits of pork loins selected to vary in color and marbling. Boneless loins (N = 288) were selected from two production focuses on 4 separate days using a VQG grading camera to represent a range in ventral color and marbling. Color, marbling, firmness, pH, and instrumental color values were evaluated on the ventral side of each loin at 1 d postmortem. Early ventral loin lightness (L*) values ranged from 52.42 (light) to 37.23 (dark) and extractable lipid ranged from 0.7% to 6.2%. Loins were then transported to the University of Illinois for further evaluation in two experiments. The goal of the first experiment was to compared correlation coefficients between early and aged pork quality traits from loins aged intact under vacuum packaging and loins aged as chops in case-ready packaging. Loins were assigned to one of two packaging treatments. 1) Aged as intact-loins in vacuum packaging at 4°C until 12 d PM (n = 144), removed from packaging, evaluated ventral quality parameters as described at 1 d PM, sliced into 28 mm thick chops, evaluated instrumental color on chop face surface, and individually re-vacuum packaged until 14 d PM. 2) Sliced at 2 d PM (n = 152) and aged as chops in case-ready packaging until 12 d PM, removed from packaging, instrumental color evaluated on chop face surface, and individually vacuum packaged until 14 d PM. Chops were packaged in individual Styrofoam trays and overwrapped in polyvinyl chloride (PVC) oxygen permeable film and gas flushed in bulk packages with a gas mixture that contained approximately 0.4 % carbon monoxide, 30 % carbon dioxide, and 80 % nitrogen. Chops CRA were stored in bulk packaging at 4°C until 9 d PM, removed from the bulk packaging, and set on simulated retail display until 12 d Pm at 4°C. At 12 d PM, chops were removed from simulated retail display and their PVC packaging, individually vacuum sealed, and stored at 4°C until 14 d PM. Warner-Bratzler shear force (WBSF) and cooking loss were evaluated at 14 d postmortem. Quality parameters of both packaging treatments at early and aged time points were compared as a completely randomized block design with slaughter date as a blocking factor. Pearson’s correlation coefficients between early and aged quality traits, and WBSF or cooking loss were transformed using Fisher’s r to z transformation for independent correlations comparisons of packaging treatments. Dependent correlation comparisons utilized transformed Pearson’s correlation coefficients between ILA ventral quality traits at 1 d PM, 12 d PM, and WBSF or cooking loss and were transformed using Fisher’s r to z transformation with an additional test statistic, t, for dependent correlation comparisons. Loins designated to ILA were 0.29 units redder (P = 0.03) than CRA loins at 1 d PM, with no other differences (P ≥ 0.13) of 1 d PM quality traits. Chops from ILA were more tender and had less cooking loss (14 d postmortem), and were darker and redder (12 d postmortem) on the chop face than CRA chops (P < 0.0001). Lightness and redness values on the ventral surface for ILA loins (r = 0.52 lightness; r = 0.63 redness) and CRA loins (r = 0.45 lightness; r = 0.61 redness) at 1 d postmortem were both correlated with aged lightness and redness values on the aged chop face at 12 d postmortem. Those correlations did not differ for either lightness or redness (P ≥ 0.43). Overall, aging intact loins in vacuum packaging improved color after 12 d of aging, while increasing tenderness and decreasing cooking loss, compared with CRA loins. Despite the differences between aging methods, the relationships between early and aged loin quality traits did not differ between aging methods. Therefore, packers need not to consider subsequent packaging and aging methods when sorting loins on early postmortem quality traits. The second experiment’s objective was to determine the interactions between packaging type and degree of doneness on sensory traits of pork loins selected to represent the newly proposed USDA quality grades. At 2 d postmortem loins were sliced into 28 mm thick chops and were randomly assigned to either individual vacuum packages or to individual Styrofoam trays and overwrapped in polyvinyl chloride (PVC) oxygen permeable film. Overwrapped PVC packaged were then placed in gas-flushed bulk packages. Bulk packages were flushed with a gas mixture that contained approximately 0.4 % carbon monoxide, 30 % carbon dioxide, and 80 % nitrogen. Vacuum-packaged chops were aged until 14 d postmortem and then evaluated for trained sensory analysis and instrumental tenderness. Chops packaged in PVC overwrap were aged until 9 d postmortem in the bulk packages, then placed on simulated retail display until for 14 d postmortem. Sensory traits and slice shear force (SSF) was evaluated after all chops were frozen and then thawed prior to evaluation. Chops from each packaging type were cooked to an internal temperature of either 63° C or 71° C. Data were analyzed as split-split plot design with production focus of the pigs, proposed USDA quality grade, packaging type, and degree of doneness as fixed effects. There were no interactions among quality grade, packaging type or degree of doneness for any traits. There were no differences in sensory tenderness (P = 0.30), juiciness (P = 0.49), flavor (P = 0.89), SSF (P = 0.13), or cook loss (P = 0.06) among USDA quality grades. There were no differences in sensory tenderness (P = 0.06), juiciness (P = 0.32), flavor (P = 0.74), SSF (P = 0.99), or cook loss (P = 0.12) between chops aged in vacuum packages or PVC packages. Chops cooked to 63° C were 4.6% more tender (P < 0.0001), 10.1% juicier (P < 0.0001), and 2.9% less flavorful (P = 0.01) than chops cooked to 71° C. Neither proposed USDA quality grade nor packaging type impacted eating experience. Cooking chops to 63° C rather than 71° C was a more effective way to improve eating experience than the newly proposed USDA quality grades or differing packaging types.
Issue Date:2018-05-09
Type:Text
URI:http://hdl.handle.net/2142/101635
Rights Information:Copyright 2018 Brandon Klehm
Date Available in IDEALS:2018-09-27
2020-09-28
Date Deposited:2018-08


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