Date Full Report Received11/27/2017
Date Abstract Report Received11/27/2017
The adoption of a pork quality grading system has the potential to change the way pork is valued by pork producers by assigning value to pork loins based on quality traits. Currently, producers are compensated for their pigs based on carcass weights and estimated carcass lean values. This means pork producers are paid based on a yield grade and little emphasis is placed on quality. In order to establish scenarios by which producers can be rewarded for producing high quality pork, a better understanding is needed of the relationships between quality evaluations made by the packer/processor and quality as evaluated by the consumer at both the point-of- purchase and when consuming pork products.
Loins (N =296) used in this project were from pigs from two different production focuses similar to those used in NPB #14-221. Carcasses were blast-chilled and then held in an equilibration cooler until approximately 22 h postmortem, when they were fabricated into primal cuts and boneless loins were further cut into boneless strap-on (longissimus costarum) center cut pork loins. Loins were randomly assigned within a production focus to target equal color and marbling scores for loins designated for aging as intact loins (n = 144) until 12 d postmortem or sliced into chops (n = 152) at 2 d postmortem and aged until 14 d postmortem as case-ready chops. Selected loins were removed from the de-boning line and subsequently evaluated for CIE instrumental lightness (L*), redness (a*), and yellowness (b*) (CIE, 1978), pH, visual color, marbling, and subjective firmness and weight. During initial evaluation at 1 d postmortem loins were randomly assigned to either project 1 (objective 1) or project 2 (objective 2 and 3). Half of the loins were aged as intact loins and stored in a dark cooler (4° C) until 12 d postmortem. At 12 d postmortem, loins were removed from their packaging and allowed a minimum of 30 minutes for oxygenation of myoglobin prior to ventral loin quality evaluation. Ventral loin evaluations at 12 d postmortem were performed by the same trained technician as conducted the same quality evaluations on 1 d postmortem. The other half of the loins were aged as case-ready chops and were removed from their vacuum sealed packaging at 2 d postmortem. Loins were then sliced into 28 mm chops. Chops were subsequently packaged in vacuum packages or placed in Styrofoam trays and overwrapped with PVC film. Overwrapped packages were placed in a gas-flushed modified atmosphere bulk package with sets of chops from a single loin placed in each bulk package. Chops were stored until 9 d postmortem. At the conclusion of the aging period, chops were placed in a simulated retail display for 3d postmortem. Then, chops were cooked to either 63° C or 71° C and evaluated for sensory tenderness, juiciness, and flavor as well as instrumental slice shear force.
No differences were expected for ventral loin quality of loins designated for aging as intact loins or loins designated as case-ready chops because they were randomly assigned to aging treatments from a single set of loins within the two respective production focuses. There were no differences in early postmortem ventral quality except for redness values of intact loins were redder (P = 0.03) than case-ready loins. Aging treatment caused the chop surface of case-ready chops to be lighter (P < 0.001) and less red (P < 0.0001) than chop face of chops from intact loins after the aging period. Chops from case-ready loins also had greater (P < 0.0001) WBSF values and cook losses (P < 0.0001) than chops from intact loins. The ventral surface of intact loins became lighter (P < 0.0001), redder (P < 0.0001), and more yellow (P < 0.0001) during the postmortem aging period. Visual color and marbling did not change during the postmortem aging period, but pH declined (P < 0.0001).
Early postmortem color values on the ventral surface of the loin was correlated with aged postmortem color of the chop surface and those correlations did not differ regardless if a loin was aged as an intact loin or as a case-ready chop. Early postmortem ventral loin quality traits were not strongly correlated with WBSF or cook loss. Those correlations did not differ between intact loins and loins aged as case-ready chops.
There were no differences in sensory traits (P ≥ 0.30), slice shear force (P = 0.13), or cook loss (P = 0.06) among proposed USDA quality grades. There were no differences in sensory traits (P ≥ 0.06), slice shear force (P = 0.99), or cook loss (P = 0.12) between packaging types. Chops cooked to 63° C were rated more tender (P < 0.0001), more juicy (P < 0.0001) but less flavorful (P = 0.01) than chops cooked to 71° C. Likewise, chops cooked to 63° C had lesser slice shear force values (P = 0.01) and cook loss percentages (P < 0.0001) than chops cooked to 71° C.
Contact: Dustin Boler
University of Illinois