Predicting loin-eye area from ultrasound and grading probe measurements of fat and muscle depths in pork carcasses

Abstract

The mathematical relationships between loin-eye area (m. longissimus thoracis) and linear measurements of fat and muscle depth were studied on digitalized images from 250 hog loins cut between the 3rd- and 4th-last ribs. Depth measurements were collected using (1) an Ultrascan 50 ultrasound system on immobilized, live animals, (2) a Hennessy grading probe on hanging carcasses under normal slaughtering conditions and (3) image analysis on digitalized images of chops separated between the 3rd- and 4th-last ribs. Loin-eye area was accurately predicted by its depth when the measurement was performed on digitalized images (R2 > 0.86; RSD < 1.87 cm2). The accuracy of the relationship between loin-eye area and muscle depth was reduced using ultrasound (R2 = 0.58, RSD = 3.29 cm2) or the probe (R2 = 0.29, RSD = 4.28 cm2) due to measurement errors on muscle depth. Muscle flatness, the perimeter irregularity or its angle in relation to the midline did not improve prediction accuracy. Consequently, muscle depth as measured by the Ultrascan 50 ultrasound system should be used with caution to predict loin-eye area since the measurement is only moderately accurate. Measurements obtained with the Hennessy probe under normal slaughtering conditions are not recommended for predicting loin-eye area in pork carcasses. Key words: Pork, backfat, muscle depth, loin-area, ultrasound, prediction