Re-Defining Pork Quality with pH
By Jane Messenger
| Tuesday, March 01, 2005
When it comes to pork quality, “good taste is just the beginning,” says Ken Prusa, Iowa State University food scientist. “Several programs address antibiotic-free or animal welfare, but these pertain to attributes, not quality. At the end of the day, we still have to look at muscle quality, and we keep coming back to ultimate pH.”
The bar is rising throughout the pork chain in terms of wanting more uniform products. “The consumer looks for consistency with color, purge and a good eating experience,” says Len Huskey, vice president of quality assurance, Swift & Company. “Pork processors also are looking for consistent raw materials that will help to guarantee these attributes.”
International markets lead this trend. “It all began with Japan, but there is increased interest and increased expectations domestically as well,” notes Huskey.
Swift and Hormel have each found that a high muscle pH leads to a product’s ability to hold moisture, an improved appearance and overall better taste for the consumer. It’s worth noting that a high pH level doesn’t impact the product’s nutritional profile, unlike a high intramuscular fat content.
When talking about pH, Prusa says a level of 5.8 or higher is desirable. “It’s a much different eating experience when you get down to 5.4 pH, which is a paler, softer product,” he notes. “A higher pH level indicates lower purge and a darker red color.” (See accompanying chart.)
Many factors influence muscle pH from the farm through the packing plant. They include everything from genetics, feeding programs, animal handling from the farm to the plant and carcass chill rate after slaughter. In terms of the critical mechanism – when an animal is slaughtered, the blood flow stops and lactic acid produced in the muscle increases. If the pH drops too rapidly, you end up with pale, soft and exudative pork.
“I have to commend producers and packers,” says Prusa. “We used to see ugly, white, PSE muscle, but recently, I saw only one case in more than 1,000 loins. With more emphasis at the production level and with the new deep-chill technologies available to packers, it’s harder to find low pH (moderate PSE) and pure PSE products.”
What does high pH offer?
According to Jerry Cannon, research scientist, Hormel Foods, high muscle pH has many advantages.
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The product has improved visual appeal, especially the color and firmness.
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Reduced purge equals higher retail yield.
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Less purge in the product tray also equals more consumer value because it looks more “normal,” less wasteful and there’s less mess to clean up.
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Improved product tenderness and juiciness.
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Increased meat-case shelf life because bright/reddish lean muscle holds its color longer than pale products.
More producer focus and education is needed to identify pigs that produce high pH pork, says Prusa. Keep in mind that you can’t test live animals for pH; it’s something the packer has to do on the final product.
Something you can do is talk to your genetic supplier. Ask the geneticist how the supplier is improving pH in its genetic lines. These days the supplier should have pH breeding values – and pH is highly heritable. Remember, there are breed-line differences and genetic differences within a breed.
Then there’s the packing plant. “Producers should request information from their packer. Look at the daily pH average of the plant and compare it with their pigs to get a running database,” says Prusa.
Huskey agrees. “Producers need to work with the packer to whom they’re marketing hogs, and see what information is available,” he says. For instance, if your packer is measuring pH, ask if your pigs can be screened so that you can compare them to the plant average.
It’s also wise to talk to your packer about feed withdrawal when shipping your pigs. Prusa and Cannon agree that 18 to 24 hours of feed withdrawal is optimal. Cannon explains that longer feed withdrawals can boost pork quality, but there are challenges as well. These include carcass weight loss after 36 hours. Current marketing programs are set up to take multiple cuts out of pens, but pigs that are taken off feed and remain in the barn may suffer growth setbacks.
Another suggestion is to become more informed on the subject of pH. You can find pH and other pork-quality information on the National Pork Board Web site at www.pork board.org. Click on the “Science and Technology” section, or contact Mark Boggess, animal science director.
Packers will eventually include pH in future procurement programs. “It’s the next step,” Prusa says. “We (pork industry) have gone about as far as we can on leanness.”
While packers know the average pH of pork in their plants, and the genetics of those hogs, they face challenges in measuring it at line speed.
Neither Hormel nor Swift have put pH in their payment systems. But there is that potential in the future, Huskey says. One obstacle is that measuring pH before a carcass is chilled reduces the predictability of ultimate pH (which is the final measurement taken 24 to 48 hours after slaughter.) Another challenge is that the producer’s identity is lost if pH isn’t measured until the carcass is cut.
“We’re working on maintaining the chilled carcass’ identity back to the farm, but don’t have the ability to do that yet,” says Huskey.
“We’re still a ways off from paying for pH, but producers could potentially address this within their market contracts, such as using specific genetics and feeding regimes,” adds Cannon.
Hormel personnel are looking at various processes that influence pH. These include the animal’s genetic makeup; nutrition and feeding regimens, including feed withdrawal; how the animal is handled in the late-finishing phase, transportation and lairage; and slaughter processes. Cannon says they’re also looking at stunning practices, time on the kill floor, carcass chilling and enhancement.
“Anything we can do to improve products, such as increasing pH, is good for us,” he continues. “Seventy-five percent of our products are further processed products where pH is important to cooking and smoking yields.” Of course, water-holding capacity is always important, especially in enhanced products, he notes.
Results from the National Pork Benchmarking audit have shown the value of high pH through enhanced products. For example, enhanced products were more tender and juicy, with less purge. Consumers paid 15 cents more per pound for those products versus non-enhanced ones because they taste and perform better.
Prusa has worked with Swift to take pH readings on boneless loins to get an idea of the packer’s general supply. Swift also will profile a specific producer’s pigs for pH on a cost-share basis if he is looking to establish a marketing contract or wants to make genetic changes.
Swift has meat-quality expectations expressed through a ranking system, called Pork IQ, that Prusa helped develop. In this system, the packer looks at different meat-quality attributes, such as water-holding capacity, color score, intramuscular fat, cooking loss, tenderness and juiciness, along with compostion and lean percent. The system helps Swift track pork quality traits of the hogs sold to its plants and determine where changes need to be made.
What does pH mean to packers? “We have to continue doing what we’re doing – profiling meat quality from specific producers and genetic types so that we know what to expect,” says Huskey. “We also have to continue working toward online pH measurements so we can have the average and range of pH values for each lot – just as we do for percent lean.”
Prusa believes retailers will have an interest in selecting pork products based on pH levels. He has worked with several large retailers on different aspects of meat quality. As retailers begin looking at pH-based products, there will be a learning curve to determine an appropriate range for pH and other meat-quality attributes. Today, when they go into packing plants retailers want to know why some international markets are getting the best pork, and why they can’t offer it to U.S. customers. Hormel is working with retailers on understanding pH and selection levels.
When retailers get serious about pH-based products, Prusa expects the packer will put someone on the processing line to select for pH. That’s what’s being done for the Japanese market, which places emphasis on color and pH. You can expect retailers to set the pH limit on products they will buy.
Cannon says retailers could use pH as a differentiation point, and packers will have to hit the mark to sell them product. Hormel is working with retailers to help them understand how selecting products for pH will provide their customers with better products.
As the bar continues to rise, the ability to measure pork-quality traits will be increasingly important to the entire pork chain. Good taste may be the beginning, but higher quality and more uniform products are the future.
