Farm-Scape, Episode 2139

Researchers in Manitoba are striving to apply the use of ultrasound to evaluate marbling in pork through readings taken on both the live hog prior to slaughter and on the carcass after slaughter.

Approximately 85 percent of the hogs that are produced in Manitoba go for export and those customers, especially in the higher value markets such as Japan, want marbling.

Breeders Reverse the Trend Away From Marbling

“Five to six years ago we had no marbling and now it's starting to creep back in,“ observes Dr. Bob McKay a research scientist with the Brandon based Swine Research and Development Corporation.

“We need the marbling if we want the export sales. Marbling adds flavor and taste to the meat.“

Dr. McKay along with his team which includes ultrasound technician Tracy Curtain and herdsmen Bob Wedderburn and Tom Curtis have kicked off a project under which they are attempting to correlate ultrasound images taken from the live hog and from the slaughtered carcass with the amount of marbling in the meat.

“What we’re doing,“ explains Dr. McKay, “is we have a group of pigs going through our barn and we ultrasound them just before we ship them for slaughter. We ultrasound the carcass within 45 minutes of slaughter and then we come in the next day after an 18 hour chill, split that carcass, because we’re probing over the last four ribs of the loin. We take that segment out, cut it parallel to the backbone so that we’re probing at the grade site and then we scan that half loin with a flat bed scanner into the computer for evaluation. Then we take that half piece of loin off the four ribs and send it away for chemical fat [analysis].“

He says, “What we’re trying to do is tie the live animal to the carcass scan to what we see visually and chemically.“

“We know what marbling looks like because we’ve also split carcasses. What we’re doing is we’re trying to quantify how much marbling is there when we look at it with the ultrasound on the live animal and also on the carcass and then tie that back to what we see when we look at the cold carcass the next day. The ultimate measure back is the chemical fat that’s in that loin sample.“

Marbling Key to Taste

The presence of marbling in the meat will have a profound effect on taste. Dr. McKay suggests, “The simple test is go to the grocery store and look at the pork chops and pick out a bunch of pork chops that have no marbling and pick out some that do have marbling. Cook them up and keep them separate and you’ll be able to tell the difference. They [un-marbled cuts] just don’t have the same taste. If they haven’t got the taste people aren’t going to buy.“

“There are many choices out there. They’re not restricted to your choice is pork or pork. If they don’t like the pork they can have beef, they can have chicken, they can have fish so we have to have a product that is desirable to the palate as well as to the eye.“

He notes, “A lot of what we sell to the Japanese market are boneless backs which is basically the loin eye muscle removed and it’s cut into chops or steaks or what ever over there. The bulk of the marbling has to be in there and if we don’t have it they’re not going to buy it.“

Discovery Described as a Fluke

The ability of ultrasound to identify the presence of marbling actually came about by chance. Dr. McKay recalls, “We were going to a show and we decided to cut some loin samples, a four rib sample over the last four ribs and cut it two inches off the mid line so we could demonstrate our probing and what we’re actually measuring. I was looking at the marbling and I went, wow look at that! I went back and looked at the image and the same pattern was there. The light went on and I said hey wait a minute, we’re actually picking up the marbling. We hadn’t noticed that before.“

He says, while the process is able to determine if there is or isn’t marbling present in the meat, it would be nice to quantify the data to determine just how much there is.

“It’s one thing to say yes there is or no there isn’t, but we have to think in terms of the end product. We have to remember what a pig is. A pig is just packaging for two shoulders, two loins, two bellies and two hams and we have to always think in terms of that end product. If we’re probing a boar for example, he’s going to be producing loins that are going to go to a Japanese market or a Taiwanese market or what ever and we have to have the quality measures. The only meat quality measure that you can measure on a live animal is marbling. Color has to be 18 hours post mortem, texture is 18 hours post mortem but marbling you can do on a live animal.“

Image Collection an Exacting Science

One down side, collecting accurate ultrasound readings is an exacting science requiring considerable expertise.

“We take three measurements,“ explains ultrasound technician Tracy Curtain. “One is a longitudinal scan and it’s the last four ribs of the pig off of the mid-line of the pig so it measures the last four ribs and measures the fat, the loin depth. We also take a belly shot which is the last four ribs as well but further down on the side of the pig by the belly and that measures the fat and the lean ratio. We also take a cross sectional image and that brings up a picture, almost like what you would see at the supermarket as a pork chop, and we do loin eye area on that one.“

She stresses, “You want to take a clean accurate measurement at the right location. If you take a poor quality image and it’s off of your designated areas you get skewed results. We have to make sure our placement is accurate and that our image that we capture is clean and clear and you can actually see what you’re looking for.“

Technology Expected to Result in Advantages Throughout the Pork Production Chain

Dr. McKay is confident this approach has potential applications for both the selection of breeding stock and for sorting carcasses at the packing plant.

“If this works out the selection of breeding stock is going to be quite revolutionary.“ He suggests, “If, for example, we’re probing [for] somebody that’s producing breeding boars it would be great if we could walk in there and say this boar has a large amount of marbling or a medium amount or a small amount or no marbling so that we can have boars, depending on your needs, that can help out a herd. If a herd has no marbling then you want a boar that has lots of marbling. If you’ve got some marbling then you don’t need to go that much.“

He continues, “More importantly there is great potential and great interest in incorporating this technology into packing plants so, when they use ultrasound grading because that’s available now, they can assess how much marbling is in the loin so that they can target specific loins for specific markets.“

He explains, “From a packing plant standpoint, if they can sort carcasses instantaneously once they’re killed as to which one has marbling and which one has enough marbling to meet a specific market it means that cutting becomes far more efficient and then you don’t have to cut a loin, for example, to check to see if there’s marbling because once you cut a loin it’s no good for the export market.“ He concedes, “That’s fantasy time to an extent but fantasy can become reality pretty quick.“

Staff Farmscape.Ca