There’s nothing better than cutting into a tender, juicy pork chop. The problem is that some consumers end up with a tough, dry piece of pork. That’s why researchers and processors are working to determine which fresh pork traits best predict a positive eating experience.

Those traits primarily involve pH (a measure of the meat’s acidity) and marbling (the visible intramuscular fat or lipid content). A higher pH indicates less acid conditions, which usually translates into a higher quality, fresh pork product. Greater lipid content is attributed to softer texture and juicier meat. (See the chart on page 16  for more information on pH effect on sensory quality.)

“Pork quality and consumer satisfaction are important,” says Steven Lonergan, IowaStateUniversity meat scientist. “The challenge is to ensure that from the production and genetic standpoint. As pork has gotten leaner, there have been more quality issues. One approach is to get more marbling into fresh pork.”

Iowa StateUniversity animal and food scientists teamed up to analyze the contribution of both pH and marbling to fresh pork quality.

In a group of fresh pork loins generated from the National Barrow Show progeny tests back in 1991, 1992 and 1994, researchers also had collected data on lean composition, pH and sensory quality. The loins are from Berkshire, Chester White, Duroc, Hampshire, Landrace, PolandChina, Spotted and Yorkshire hogs.

Ken Stalder, IowaState animal scientist, explains those were the only years that researchers collected individual fatty acid information. But he says the data is still informative today. “Individual fatty acids make up intramuscular fat; it actually tells us about the relationship between sensory quality traits and pH,” says Stalder. “Those relationships still exist and are applicable today.”

After accounting for variation in the readings due to year, breed, gender, test date and halothane genotype, researchers could determine the contribution of lipid (evaluated chemically) and pH to fresh pork tenderness, chewiness and juiciness.

“The results show that a higher pH creates a more tender and juicy fresh pork loin,” says Lonergan.

Researchers also determined that at a high pH­ (greater than 5.8) lipid content did not improve fresh pork’s sensory quality. That’s likely because the product already had a superior sensory quality, texture and cooking-loss traits, so lipids could not contribute anything more. Therefore, adding lipids generally will not improve this product’s sensory tenderness, chewiness or juiciness.

Conversely, at low pH (less than 5.5), the pork product started with inferior quality in virtually every category. In other words, the product had sufficient quality challenges that couldn’t be overcome with intramuscular fat. Under those conditions, increasing lipid levels did not improve pork quality, points out Lonergan.

Only at intermediate pH levels (between pH 5.5 and 5.8) did lipid content improve the pork-loin sensory evaluation. While lipid content does improve pork sensory traits at intermediate pH levels, the study showed that only a small portion of the variation can be attributed to lipid content.

Still, Stalder says that pork producers would benefit by selecting for intramuscular fat levels, if for no other reason than to make slight improvements in some of the sensory traits, which could add to consumer acceptance. Many upscale restaurants and export markets demand intramuscular fat levels that are typically greater than levels found within average pork loins today. But, that’s mostly a flavor issue.

So, pH is gaining clout in terms of being the influential pork quality trait. One drawback is that any number of factors can affect lean-muscle pH, such as handling, transportation, inappropriate feed withdrawal and more.

Then there’s the fickle consumer factor. “When consumers select pork products, what they think they want is different than what they actually choose during a taste panel,” explains Stalder. In the raw state, consumers consistently select the leanest possible cut. “Some research has demonstrated that consumers actually prefer to eat pork with higher marbling content than they would select when choosing between packages of fresh pork cuts.”

Still, if a consumer cooks a pork chop and trims the external fat, he/she could have 5 percent intramuscular fat and have a 95 percent fat-free product. That 95 percent fat-free level is often touted as a desirable target.

As a producer, one thing you can do is talk to your genetic supplier. Find out how the supplier is improving pH, as well as other pork quality traits in his genetic lines. The supplier should have pH breeding values — and, pH is a highly heritable trait. Remember, there are significant breed-line differences as well as genetic differences within a breed.

Then there is the packer/processor’s role. You can’t test live animals for pH; it’s something that the packer has to do on the final product. But you should request and evaluate the pork pH readings collected from your hogs. Also, ask if you can compare them to the plant average.

Additionally, review and discuss how the pigs are handled on their way to the packing plant, once they’re at the plant and after they begin the harvesting process. All of those factors can contribute to pork quality issues.

Feed withdrawal is another factor. As a rule, an 18- to 24-hour withdrawal is optimal. Longer periods can boost pork quality, but there are challenges, including carcass weight loss after 36 hours.

This research is one more validation that monitoring pH and lipid levels can mean higher quality pork products for consumers. That in turn gives them even more reason to buy pork on a regular basis, which could help secure and increase domestic and foreign demand of U.S. pork products.


pH Effects on Pork Quality

This chart shows that pork products with higher pH are more tender and juicy than those with lower pH readings. Higher pH means lower acidity, which traslates into a better eating experience for consumers.

Sources: Steven Lonergan, meat scientist, and Ken Stalder, animal scientist, IowaStateUniversity.