Correlation of fresh muscle firmness with sensory characteristics of pork loins destined for export to a quality focused market

Abstract Text: Because pork processors use subjective firmness at 1d postmortem to sort loins for quality-driven export markets, the objective was to correlate firmness at either 1d or 28d postmortem with sensory characteristics.  Boneless loins (N=154; 2.86-5.58kg) were aged for 28 days at 1.7°C.  Firmness was assessed at 1d postmortem using a 5-point subjective scale at the 10^th rib. On 28d, subjective firmness scores were assigned using the same scale on the ventral side of the loin at three locations: the area of the 10^th rib, the anterior half, and the posterior half.  Durometer readings were collected at the 10^th rib on both dorsal and ventral sides of the loin and then averaged for average loin objective firmness. Loin flop and circumference were measured. Chops were cut and frozen on 28d to assess sensory, quality, and mechanistic characteristics.  Data were analyzed using the correlation procedure of SAS with Spearman correlation coefficients to account for the non-normality of data.  Subjective firmness measures on 1d and 28d postmortem were correlated to 28d loin flop distance and loin circumference (P<0.01). Dorsal and ventral durometer readings at 28d postmortem were not correlated to these traits (P>0.30).  Day 28 subjective loin firmness was negatively correlated with purge loss and accounted for between 7.3% (10^th rib) and 12.0% (anterior portion) of the total variation in purge (P<0.01).  Though 1d subjective firmness accounted for 3.0% of the variation in 28d Warner Bratzler shear force (WBSF; P=0.03), 28d subjective firmness measures were not correlated to WBSF (P>0.36).  Sensory tenderness was weakly correlated with subjective anterior firmness (P=0.03; r=0.17), but no other firmness measures.  Sensory chewiness was weakly correlated with 28d 10^th rib and anterior firmness (P<0.05; r= -0.18 and -0.19, respectively).  Day 28 loin dorsal durometer readings accounted for 3.6% of the total variation in sensory juiciness (P=0.02), and 1d and 28d subjective anterior firmness tended to correlate with juiciness (P≤0.10; r=0.14 and 0.13, respectively). Averaged 28d loin durometer readings and 1d subjective firmness measures did not correlate with sensory characteristics (P≥0.10).  Initial (1d) firmness accounted for 4.0% of the variation in intramuscular fat iodine value (P=0.02). No firmness measures correlated with soluble or insoluble collagen content (P>0.05).  These results suggest that 1d postmortem firmness measures do not correlate to pork quality or sensory characteristics at 28d.  Although a small amount of variation in sensory attributes can be explained by 28d firmness measures, results are not consistent throughout the loin.

Keywords: Firmness, Quality, Sensory