Farms, Slaughter Plants Share Pork Quality Responsibilities

University of Illinois researchers recently discovered farm-of-origin and slaughter plant can have a big impact on pork quality.

Members of the pork industry are very aware that a meat case full of pale, soft and exudative (PSE) pork products is not very consumer friendly. Consequently, some packers have threatened to penalize producers for poor meat quality. Researchers noted that many factors work together to influence pork quality.

Previous research has shown quality attributes such as loin color, water-holding capacity and incidence of PSE pork are affected by genetics, animal handling and pre-slaughter management. Illinois researchers recognized that little information is available about how farm-of-origin and slaughter plant may cause variation in fresh pork quality under commercial conditions.

As part of the research project, a total of 4,500 commercial hybrid pigs were harvested at two slaughter plants on four different days. The pigs originated from four different farms, but all represented the same genetic line. The four slaughter days were spread out over the seasons, with one day falling within the spring, summer, fall and winter.

One truckload of pigs from each farm was sent to each plant on the respective slaughter days. Pigs were slaughtered following an overnight rest period. Eight hundred pigs were randomly selected for meat quality evaluation. The sample was broken down as 25 pigs/farm/plant/slaughter day.

The researchers found considerable pork quality differences between the two plants. One plant produced pork with greater loin pH, improved tenderness and juiciness, and lower purge loss and drip loss. Pork from this plant was darker in color, juicier and more tender. The product also had greater water-holding capacity.

Researchers were surprised to find great pork quality differences between the farms, too, particularly in terms of loin pH and water-holding capacity. Research results also suggested the slaughter plant which generated the most desirable loin quality differed among the four farms, meaning there were significant farm-of-origin by slaughter plant interactions for most of the important pork quality attributes.

The researchers say results from this study highlight the importance of optimizing conditions during the final crucial steps before slaughter. This includes focusing on the pork quality implications at the farm, during handling and transport procedures and at the slaughter plant.

Researchers: Dan Hamilton, Brian Bidner, Floyd McKeith and Michael Ellis, University of Illinois. Contact Ellis at (217) 333-6455, or email mellis7@uiuc.edu.

Baking Soda Resolves Long-Standing Pork Quality Problems

Quality problems due to pale, soft and exudative (PSE) pork have plagued pork products for more than 50 years.

Efforts to reduce this problem through genetics or rapid postmortem cooling have proven only partially successful.

Depending on the breed, 5-15% of hogs produce PSE meat. The pigs are healthy, but the pork is of inferior quality.

A research team at the University of Wisconsin has addressed this problem by injecting a compound long used for baking and treating indigestion — baking soda or sodium bicarbonate — into the meat right after slaughter.

Researchers note that PSE occurs because of natural changes in muscle chemistry. Meat from all animals typically becomes more acidic after slaughter. But meat from PSE pigs becomes acidic too rapidly. When that happens, the meat loses water and becomes pale and soft.

To deal with PSE problems, the Wisconsin research team developed and patented a technique that controls the acidity of the meat. A sodium bicarbonate solution is injected into loins, hams and other cuts, where it diffuses throughout the tissue and lowers acid levels.

In a trial of 16 halothane-positive gilts, at approximately 15 minutes after slaughter, sodium bicarbonate was injected into meat cuts from half the carcass of a PSE animal. The other side of cuts was left untreated.

All concentrations resulted in a higher ultimate pH, improved muscle color and reduced drip loss.

In a second experiment, the compound was injected into muscle tissue from 23 pigs at either 15 minutes or 24 hours after slaughter. PSE meat injected at 15 minutes postmortem was superior to meat injected 24 hours postmortem in all areas except in reducing drip loss.

From this work, researchers determined they could slow the rate and reduce the level of acid development in the muscle of PSE pigs to the extent that water-holding capacity and meat color were similar to meat from non-PSE pigs.

The treatment seems to reverse the affect of the PSE condition through the muscle structure actually opening up and retaining more fluid, which causes the meat to become less pale.

The injection process has been patented by the Wisconsin Alumni Research Foundation. Hormel Foods, based in Austin, MN, acquired the exclusive license to the technique and is using the compound on fresh, shelf-ready, retail pork cuts.

Researchers: Robert Kauffman, Marion Greaser and Ronald Russell, University of Wisconsin; Ed Pospiech, visiting scientist from Poland. Phone Kauffman at (608) 238-7878 or e-mail rgkauffm@facstaff.wisc.edu.

Berkshire Meat Quality Not Affected by Paylean

Michigan State University researchers say Paylean may be used to improve the growth rate and lean yield of Berkshire-sired pigs, without impacting their superior pork quality.

Paylean (Elanco) is the trade name for ractopamine hydrochloride. This repartitioning agent causes a pig's metabolism to shift nutrients from fat to muscle growth.

Researchers compared Berkshire-sired and Yorkshire-sired pigs to Berkshire-sired pigs fed Paylean (supplemented at 9 g./ton of ration for the last four weeks of finishing). The Berkshire-sired pigs not fed Paylean served as the controls.

Sixteen pigs were assigned to each of the three experimental groups at a weight of approximately 180 lb. All pigs received a diet containing 16% crude protein and 0.9% lysine. Growth traits were not statistically analyzed due to limited pen numbers.

The Berkshire-sired pigs receiving Paylean and the Yorkshire-sired pigs had 19% higher average daily gain and 18% higher feed efficiency than Berkshire control pigs.

Pigs were slaughtered over two days at a commercial packing plant. Carcass weights did not differ among groups. Berkshire-sired pigs fed Paylean and Berkshire-sired pigs fed Paylean and the Yorkshire-sired pigs produced carcasses with larger loineye areas, heavier hams and more total fat-free lean than the Berkshire control pigs.

Yorkshire carcasses had lighter bellies, less 10th rib and average backfat and a higher percent fat-free lean than both the Berkshire control and Berkshire pigs fed Paylean.

Loin muscle pH was similar at 20 minutes, 45 minutes, three hours and 24 hours postmortem for both the Berkshire groups. However, the carcasses of the Berkshire pigs fed Paylean had higher 20-minute pH and 45-minute pH than the Yorkshire carcasses. Both Berkshire groups had higher three-hour and 24-hour pH than the Yorkshire carcasses.

Berkshire pigs fed Paylean had lower 20-minute loin muscle temperatures than both the Yorkshire and Berkshire control groups, and lower 45-minute temperature than Yorkshires.

Fluid loss was higher in Yorkshire than in Paylean-fed Berkshire pigs, and tended to be higher in Yorkshire loin muscle vs. Berkshire control groups. Yorkshire loin muscle had higher purge loss than both of the Berkshire groups when stored for seven days postmortem in vacuum packaged bags at 4°C (39.2°F). Loin chop tenderness did not differ between groups.

Researchers say Paylean helped the Berkshire-sired pigs improve loineye area by 1 sq. in., wholesale ham weights by 1.2 lb. and increase fat-free lean by 5 lb. Carcass backfat thickness was not reduced.

The Berkshire progeny receiving Paylean were similar to the Yorkshire control pigs in average daily gain, feed efficiency, loineye area, wholesale ham weights and pounds of fat-free lean. The Paylean treatment did not have any adverse impact on pork color, water-holding capacity or cutability of Berkshire progeny.

According to the researchers, results suggest Paylean may be used as an effective management tool to improve growth rate and cutability of genetic lines with superior pork quality that have not been commercially accepted. If used appropriately, Paylean supplementation could allow pork producers the flexibility to utilize genetic lines with superior pork quality, explore niche markets and prevent sacrificing economically important production traits of growth rate and carcass muscularity.

Researchers: M.J. Ritter, C.P. Allison, and M.E. Doumit, Michigan State University. Contact Doumit at (517) 355-8452, ext. 203, or e-mail doumitm@msu.edu.

Harvest Process Influences Pork Loin, Ham Quality

Iowa State University (ISU) research recently demonstrated typical pork industry carcass dwell times — the interval between sticking and scalding during the slaughter process — may be too long.

Previous recommendations suggested minimum dwell times of five minutes, and a maximum of 10 minutes.

By reducing dwell times to a maximum of five minutes, carcasses can move to the chilling stage much faster and pork quality may be improved.

Removing heat from the carcass early in the harvest process can have significant pork quality implications, too. Therefore, with funding from the National Pork Board, researchers set out to identify the extent to which dwell time between exsanguination and scalding can influence pork color and water-holding capacity.

The experiment included 32 Duroc x Yorkshire crossbred barrows and 32 Duroc x Yorkshire crossbred gilts. The pigs weighed an average 248 lb. at slaughter. Eight barrows and eight gilts were slaughtered per week over a four-week period at the ISU meat laboratory. Researchers utilized a two-by-two treatment arrangement, with 16 pigs per treatment combination.

Carcasses were held for five or 10 minutes after sticking before entering the scald tank. Carcasses spent five or eight minutes in the scald tank at a water temperature of 60°C. (140°F.).

Temperature and pH were measured on the inside ham muscle (semimembranosus) and loin muscle (longissimus) at 45 minutes, two-, four-, six- and 24-hours postmortem. All carcasses were placed in the cooler at 50 minutes postmortem.

Hams and loins were removed from the left side of the carcass at 24 hours postmortem. Two, 2.5-cm. (1 in.) chops from the last rib region of the loin were used to determine subjective scores of color, firmness, wetness and marbling. Drip loss and Hunter L*, a* and b* values were measured on longissimus chops from the center loin.

The sirloin end of the loin was utilized to determine purge loss in a vacuum package over a six-day storage period. Hunter L, a, and b values were obtained on the semimembranosus and biceps femoris of the ham. Researchers recorded ultimate pH of the semimembranosus and biceps femoris from each carcass. Approximately 3.3-lb. portions of the semimembranosus and biceps femoris were utilized to determine purge loss in a vacuum package for a six-day period.


Results

The first two minutes after sticking yielded 97.57% of the total amount of blood collected (Figure 1). The researchers say there is evidence that processing facilities can decrease dwell time prior to scalding because very little blood was collected after two minutes Decreasing the dwell time would allow carcasses to enter the cooler sooner after postmortem, which may improve overall pork quality.

The researchers sought to determine the impact of early postmortem processing traits on overall pork quality. Scald time, dwell time, harvest date and sex of the animal were the independent variables in the analysis.

The longer scald time tended to result in a lower loin pH at 45 minutes and at two-hours postmortem (Figure 2). Researchers observed lower temperatures at two hours postmortem in the semimembranosus muscles of the carcasses in the shorter scald time treatment groups (Figure 3). No consistent effect of dwell time was observed (Figures 4 and 5).

These observations suggest a change in the harvest procedure has the potential to alter pH and temperature in the early postmortem period. Slowing down the rate of pH decline and increasing the chilling rate both have potential to improve pork quality.

Although the harvest treatments appeared to minimally influence pH and temperature decline early postmortem, treatment effects on pork quality measures were not consistently observed.

The data summarized in Figure 6 shows that shorter dwell and scald times did not negatively influence pork quality. According to the ISU research, it seems lengthening the period between stunning and evisceration may be detrimental to tenderness of fresh pork. This observation should be investigated further. Click here to download figures. (This requires Adobe Acrobat Reader, download at: www.adobe.com.)

Researchers: Steven Lonergan and Matt Gardner, Iowa State University. Contact Lonergan at (515) 294-9126, or e-mail slonerga@iastate.edu.