Improving the quality of pork presented to consumers has become increasingly important to the entire pork chain - from the producer through the retailer. Unlike backfat thickness, which is relatively easy to measure using several types of measurement methods with comparable accuracy, pork quality requires many measures, often with poor consistency.
Most packers have tried several on-line quality measurement systems to sort carcasses for quality prior to chilling and cooler storage. There have been few successes in this quest to date.
The NPPC Quality Lean Growth Modeling project provided a good sample of pigs that had genetic type, diet, sex, HAL (halothane) genotype and weight documented. In addition, an extensive set of loin and ham quality measures were taken on each pig in the project. The quality measures shown in Table 1 are described here:
48-hour loin drip loss - this is a good measure of purge from the loins.
48-hour loin pH - high pH (5.8 or higher) is associated with better tenderness and low drip loss.
48-hour ham pH - high pH (5.8 or higher) means less cooking and processing loss.
Loin Hunter color - loin color is measured with a Colorimeter; the lower the score the darker the meat.
Ham Hunter color - ham color is also taken with a Colorimeter; again, lower scores mean darker meat.
Loin lipid content - percent intramuscular fat by lab analysis.
Cooked loin Instron measurement - a good tenderness measure where lower scores are best.
Sensory panel loin juiciness - taste panel scores of cooked-loin juiciness; higher is better.
Sensory panel loin tenderness - taste panel scores of cooked-loin tenderness; higher is better.
Loin cooking loss - percent weight loss by cooking loin; less is better.
The packer's on-line measures for the QLGM project included both commercial and experimental equipment. Not all of the measures were used for all of the pigs. However, each piece of equipment measured at least 500 carcasses. The measurement methods included:
Fat-O-Meater reflectance: This is a light reflectance measure captured when the Fat-O-Meater probe passes through the layers of fat and muscle in the carcass. Backfat and loin thickness are reported along with the reflectance measurement.
Meat Check probe: This probe was inserted into carcasses about three hours after slaughter.
Bind-O-Meter probe: Measured pressure on a cut loin surface.
Tetrapolar electrode: This prototype from Purdue University measured electrical conductivity. Data was too inconsistent to report.
pH probe: Loin pH was measured three hours after slaughter.
Table 1 summarizes the relationship of on-line measures with various loin and ham 48-hour, post-slaughter quality measures.
The Fat-O-Meater reflectance did not relate to any quality measures. This has been found in other trials. The manufacturer makes no claims for quality measures.
The Meat Check probe seems to be closely related to 3-hour loin pH measures. However, there were few, 48-hour quality measures that were related to Meat Check probe measures.
The Bind-O-Meter had practically no relationship with 48-hour quality. This is an experimental measure that may be further revised.
Best of the on-line measures was loin pH taken at 2-3 hours post slaughter. However, the loin and ham pH are changing for at least 12 hours post slaughter, so this is only an approximate measure. A correlation of .80 or higher would give most people confidence that one trait was a good indicator of another.
The table shows the 3-hour loin pH measure has a correlation of only .54 with the 48-hour loin pH. Likewise, the 3-hour ham pH measure has a correlation of only .50 with the 48-hour ham pH measure.
Best Quality Measure? Measurement of loin pH or ham pH at slaughter is the best of a poor group of measures. Practical problems include large, day-to-day variation in plant pH levels, line-speed measurement of pH, and large number of carcasses changing pH between slaughter and 48 hours.
As a final quality measurement, 48-hour loin pH is quite desirable because it is closely related to economically important traits such as color, drip loss, cooking loss, tenderness and juiciness. Ham quality traits, such as cooking yield and tenderness, are also better at a higher, 48-hour pH.
Packers Pay For Quality? What are the possibilities for on-line measurement and packer payment programs for quality?
Clearly, measurement of every carcass for quality is not yet feasible for modern packing plants. Many researchers and manufacturers are working on more accurate measures that could be captured at normal packer line speeds.
The practical approach being taken by several packers is to develop a producer database for quality. These packers are measuring a sample of each load of pigs (every fourth or fifth carcass, for example) to get a rolling average of quality from a source; pH is most commonly used. Eventually the packer will have a database on each producer-supplier including genetics, nutritional program, herd health status and pork quality measures. This information may then be used to influence base pricing and/or contracting opportunities in the future. If this type of packer referencing system is successful, on-line quality measurement of each carcass may not be necessary to establish premiums and discounts.
Producer Approach How should producers address pork quality issues? Currently the best procedure is constant communication with your packer regarding the quality sampling results on your hogs.
Any sampling program is subject to occasional "odd sample" results. Producers should be aware of any group of pigs that produced unusual results, particularly in the developmental stages of these programs.
Both genetic type and pig nutritional programs have large effects on pork quality. Producers should work with packers to establish a new database for their hogs whenever genetic types or nutritional programs are changed. This is important, otherwise pigs from the new programs will be averaged in with the old data base and producers will not realize the full benefit of their improved quality.
Pork quality is a key issue for the industry. Although the approaches taken to measure it may not be straightforward, communications among everyone in the pork chain will be essential.