41 Characterizing the amount and variability of intramuscular fat deposition throughout the loin using barrows and gilts from two genotypes

Abstract

Pork quality is evaluated by commercial processors along the ventral surface of whole boneless loins. However, in retail settings boneless chops are evaluated individually for quality. The objective was to determine the variability in marbling attributable to chop location, sex, and sire line. The population of pigs evaluated were sired by commercial duroc boars selected for meat quality (MQ; n=96) or lean growth (LG; n=96) and equally split between sexes. Upon slaughter and fabrication, bone-in chops were removed from four locations along the loin (A=6th rib, B=10th rib, C=last rib, D=4th lumbar). Pairs of chops from each location were used for visual color, visual marbling, and subjective firmness, Warner-Bratzler shear force, and determination of moisture and extractable lipid (IMF). Variability across location, sex, and sire line was measured using a Levene’s test and the VARCOMP procedure of SAS was used to evaluate the proportion of variability each contributed to total variance. Barrows produced chops with greater IMF (3.64%) and variability (P< 0.001) than gilts (3.20%; P< 0.001). Chops from MQ pigs exhibited greater IMF (4.02%) and variability (P< 0.001) than LG (2.82%; P< 0.001). Chops from location A (3.80%) and D (3.77%) had greater IMF than B (3.34%; P< 0.001) with all three locations greater than C (2.77%; P< 0.001). Variance (s2) also differed (A=1.44% B=1.59% C=1.05% D=2.18%; P< 0.05) across chop locations. Of the variability in IMF, 33.0% was attributed to sire line, 10.16% to chop location and 4.01% to sex, with 52.83% unaccounted for. Location A chops were the most tender (2.57kg; P< 0.001) and C chops the least tender (2.93kg; P< 0.01). No differences in variability (s2; P=0.40) of tenderness were observed across chop location (A=0.31kg B=0.24kg C=0.24kg D=0.23kg). In conclusion, chop location, sex, and sire line all contribute to the amount and variability of pork loin marbling. Supported by National Pork Board Grant #18-118.

Performance of a Handheld Near-Infrared Spectroscopy Device to Predict Pork Primal Belly Fat Iodine Value and Loin Lean Intramuscular Fat Content

“…Variation was intermediate for belly fat PUFA, n-3, n-6 (CV = 15–30%), and the greatest variation was observed in chop lean IMF (CV > 30%). The mean chemically extracted fat % of chop lean (IMF) observed in this study (IMF = 3.91%) was comparable to the mid-loin IMF percentage calculated by chemical extraction (IMF = 2.70% IMF) in a prior study by Uttaro et al [ 8 ] Additionally, a study assessing IMF in various locations in pork loins of different sex and sire lines reported a range of 73.40–74.33% moisture in loin chop samples across sex and breed lines and a range of 2.77–4.02% extractable lipid of loin chops in the same animals, which are also comparable to the results reported in the current study [ 9 ]. The belly fat calculated IV in this study (mean IV = 68.0) was comparable to the belly fat IV calculated in a prior study (n = 52.5) by Lam et al [ 10 ] using fat from the outer layer of the posterior belly subcutaneous fat, as well as a study assessing pork subcutaneous fat of belly, ham, loin, and shoulder cuts (n = 162) was similar (mean IV = 68.54) [ 11 ].…”