Addressing Eating Quality Traits In Fresh Pork Products

To provide products that consumers prefer, pork processors have worked to learn more about the traits in fresh pork that can help predict eating quality.

These traits include pH (a measure of the acidity in meat) and marbling (the visible intramuscular lipid). A higher pH means less acidity and expectations for a higher-quality fresh pork product. Greater lipid content has often been linked to softer texture and juicier product.

Animal and food scientists at Iowa State University conducted an analysis to determine the relative contribution of both of these traits to fresh pork quality.

Researchers examined data from a group of fresh pork loins from the National Barrow Show progeny tests in 1991, 1992 and 1994, focusing on composition, pH and sensory quality. Loins from Berkshire, Chester White, Duroc, Hampshire, Landrace, Poland China, Spotted and Yorkshire pigs were represented.

After accounting for variation due to year, breed, gender, test date and halothane genotype, the contributions of lipid (determined chemically) and pH to fresh pork tenderness, chewiness and juiciness were determined.

In general, lipid was not shown to be a good indicator of eating quality. However, high pH consistently resulted in fresh pork that was more tender and juicy.

At higher pH (greater than 5.8), lipid did not improve fresh pork sensory quality. This was likely because the product was of superior quality at high pH. At low pH (lower than 5.5), the product was neither tender nor juicy. Under these conditions, adding lipid did not improve pork quality.

The results suggest that high pH product (above 5.8) is superior to lower pH product for sensory quality, texture and cooking loss.

In general, at high pH, adding lipid doesn't improve tenderness, chewiness, juiciness or star probe values. At low pH (below 5.5), pork is of inferior quality in virtually every category. At low pH, greater lipid content doesn't improve pork quality.

Lipid content does contribute to pork sensory traits in pork loins with intermediate pH (between pH 5.5 and 5.8). This effect of lipid content within the intermediate pH classifications indicates that only a small portion of the variation in sensory quality can be attributed to variation in lipid content.

Researcher: Steven M. Lonergan, Iowa State University. Contact Lonergan by phone (515) 294-9126, fax (515) 294-9143 or e-mail slonerga@iastate.edu.

Halothane Gene Still Exists In Small Numbers of Hogs

The halothane gene mutation (HAL-1843) still is relatively widespread in the U.S. hog population, but apparently at a relatively low level, according to a survey of packing plants conducted by researchers at the University of Illinois. The gene was detected in about 11% of farms that were represented.

Tissue samples were collected from 2,018 hogs processed at four Midwest packing plants, including 644 dead on arrival (DOA), 725 non-ambulatory, non-injured (NANI) and 649 normal pigs to determine the frequency of the halothane gene. The sampled pigs originated from 454 farms, transported on trailers averaging 152 pigs/load at an average weight of 275 lb.

Frequency of the HAL-1843 gene was only 2.7% of the total pigs sampled being either homozygous recessive (two copies of the gene) or carriers (one copy of the gene) for the mutation, and 97.3% of pigs being homozygous dominant for the normal allele gene (no stress genes).

The 55 pigs with at least one copy of the mutation came from 53 different farms, suggesting that the mutation was relatively widespread. Of the 11% identified as carrying the mutation, 2% of the farms had homozygous-recessive animals and 9% had carrier animals.

There were differences among plants in the frequency of carrier animals, but the differences were modest and a larger study would be required to detect any difference in the frequency of homozygous-recessive animals between the plants.

The gene mutation was found in all three classes of pigs tested — 1.8% of normal, 1.8% of NANI and 4.7% of DOA animals having at least one copy. There was a higher frequency of carriers in DOA than normal and NANI pigs (3.74 vs. 1.64 and 1.61%, respectively).

However, the frequency of the mutation was low in all classes, suggesting that although this mutation may be a factor in transport losses for individual animals, it is not a major cause. Therefore, efforts to reduce transport losses should focus on other genetic and non-genetic causes.

Researchers: M. Ellis, M.J. Ritter, G.R. Hollis and J.M. Schlipf, University of Illinois. Contact Ellis by phone (217) 333-6455, fax (217) 333-7088 or e-mail mellis7@uiuc.edu.