Quality Lean Index is used to educate carcass contest participants about pork quality. It is also changing what it takes to win a Missouri hog show.

Pork quantity measured as percent lean wins state fair carcass contests. Pork quality measured in pleasant eating experiences wins the appetite of hungry consumers. But where is the balance between pork quantity and pork quality?

The Quality Lean Index (QLI) was developed at the University of Missouri to educate carcass contest participants about the importance of pork quality. The developers received the National Pork Producers Council innovation award for education at the Midwest section of the American Society of Animal Science for their efforts.

“Traditional carcass contests have rewarded production of very high lean content,” explains Missouri meat scientist Eric Berg. “When this concept originated, the industry was striving to produce leaner pigs. Now the expectations have shifted back toward moderation and emphasis on pork quality.”

Berg, Bill Lamberson, Missouri animal science professor, and Tim Safranski, state swine breeding specialist, developed the QLI.

The QLI uses carcass lean percent, Hunter L* value and pH to grade carcasses.

The Hunter L* measures the intensity of light reflectance and was chosen as a variable because of its association with consumer perceptions of fresh pork color.

Quality measurements are taken from the ham, thus avoiding cutting and devaluing the loin or belly to measure 10th rib backfat for contest carcasses.

Real-time ultrasound determines the backfat and loin eye area prior to slaughter.

Doing the Math

The mathematical equation developed for the index is QLI = (7.76 % lean) - (0.067 % lean2) - (1.9995 L* value) + (1.62 pH). The photographs and Table 1 illustrate how the QLI is used to judge two carcasses.

  • Percent lean The carcass lean content is determined by a certified ultrasound technician before slaughter.

  • Percent lean squared This variable is added to the index because of the negative correlation between very heavy muscled pigs and meat quality.

  • Color evaluation The QLI uses HunterLab MiniScan XE Plus spectrophotometer on the Gluteus medius muscle, the large muscle on the cut surface when the ham is removed from the carcass. Quality measures in this ham muscle have a high correlation to the color and pH of the loin muscle.

  • Muscle pH Obtained with an SPK pH-Star glass-tipped pH probe by insertion into the same ham muscle. The ultimate pH of normal meat is 5.5 to 5.7. Higher pH leads to a shorter shelf life for pork products, and lower pH is associated with acidity and drip loss.

Interest from Producers

Interest in the QLI is growing among the state's commercial swine producers, who are coming back to carcass contests, Berg says.

“Producers have recognized the direction and focus of the pork quality chain,” he says. “They enter these contests with the goal of obtaining information about the quality of their pigs, and actually winning the contest is a nice reward for being progressive in their management.”

The Missouri Pork Producers Association and the university have begun featuring the QLI at seminars for commercial producers.

The QLI was used to judge the 2000 Missouri State Fair barrow carcass show. A number of county market hog shows have incorporated use of the QLI, Safranski says.

Interest is also growing among organizers of barrow carcass contests in Ohio, Tennessee and Iowa, researchers say.

The hogs bred for barrow shows aren't the same as those commercially produced for meat, but Berg finds similarities.

“The show ring can be considered either an artificial representation of the industry or can be looked upon for trends in the future of pork production,” he says.

As with many “contest” environments, the hogs at the Missouri shows were becoming freakishly huge and atypically lean, Berg says. The QLI completely changed what type of hog participants need to win.

“I was surprised that the QLI was so widely and positively accepted by the Missouri show jocks,” he says. “It meant retooling and rethinking the efforts expended in winning a carcass contest.

“This also tells me they are aware of the direction of the industry regarding production of high quality pork and toward the ultimate goal of total customer satisfaction,” Berg says.

Table 1. Comparison of Two Carcasses Ranked by the Quality Lean Index
Carcass #1 Carcass #2
Percentage of carcass lean = 64% Percentage of carcass lean = 58%
Percentage carcass lean2 = 4096 Percentage carcass lean2 = 3364
Hunter L* value = 60 Hunter L* value = 48
Ham Gluteus medius muscle pH = 5.48 Ham Gluteus medius muscle pH = 5.64
Quality Lean Index Quality Lean Index
(7.76 64%) - (0.067 4096%) - (1.9995 60)
= (1.62 5.48) = 103.12
(7.76 58%) - (0.067 3364%) - (1.9995 48)
= (1.62 5.64) = 137.85
Carcass #2 has a superior Quality Lean Index