DSM Corporate | | Print | A A A

Vitamin C and meat quality

Although swine and most other livestock species begin synthesizing vitamin C early in life, researchers have reported promising benefits to health, performance and (or) meat quality with dietary vitamin C supplementation under various conditions. Now, a series of studies at Iowa State University (Kremer et al., 1999) has shown significantly better color and water retention of pork during retail display when pigs received a single feeding of vitamin C shortly before processing.

Poor color and water seepage in retail packages remain serious concerns for the swine industry, even though breeding companies have largely rid their lines of the halothane gene that predisposes pigs to produce pale, soft, exudative (PSE) pork. Other causes of these meat quality problems have not been fully identified, but at the cellular level they have long been associated with the reduction in muscle pH that follows slaughter.

More specifically, studies have linked seepage problems to postmortem glycolysis, or the conversion of glucose and other carbohydrates to lactic acid in the muscle. Kremer et al. (1999) and several previous researchers also linked postmortem glycolysis to poor meat color. Vitamin C supplementation is believed to limit these changes because the body converts excess vitamin C to oxalate, which inhibits the glycolytic enzyme pyruvate kinase.

Researchers have noted improvements in meat quality with vitamin C supplementation at least since Rajic (1971) reported an increase in the muscle color scores of pork from supplemented pigs. However, these earlier studies used relatively low levels of vitamin C in long-term supplementation regimens. Kremer et al. (1999) provided much higher vitamin C supplementation in a single feeding four hours before the pigs were sent to the packer. The researchers chose this timing to optimize oxalate concentrations and minimize glycolysis after processing.

Fortification levels in the Iowa State studies were 783 and 2,348 ppm. These levels provided average one-time vitamin C intake per animal of 290 and 704 mg, respectively. The supplemented pigs were estimated to have body-water concentrations of oxalate equivalent to two and six times the inhibitory constant for pyruvate kinase in the muscle at processing.

Muscle pH was then measured in the right longissimus (LM) muscle at 22, 45, 90 and 180 minutes postmortem. Researchers have associated PSE pork with an ultimate pH of 5.5 or below. In this work, none of the muscle declined to that level during the 180 minutes after slaughter. However, muscle from both supplemented groups had a significantly higher pH (P < 0.13) than muscle from the controls (Table 1).

These results would be of particular interest with genetic lines that tend to have a lower pH than the pigs in the Iowa State study, and thus have a stronger risk of PSE meat. At the same time, however, the Iowa State researchers also noted that the rate of pH decline is an important factor in subsequent water loss, independent of ultimate pH. In this work, differences in muscle pH between supplemented and unsupplemented animals increased with time.

The carcasses were then chilled to 32°F (0°C) for 24 hours, and the LM and semimembranosus muscles were cut into chops. Meat quality results for each treatment were similar for chops from both muscles. The authors noted that this demonstrated that vitamin C supplementation was effective at improving pork quality under the different conditions that exist in the two muscle types.

Water loss during storage was less (P < 0.15) for muscle from supplemented pigs than for controls, and again the difference increased over time (Figure 1). In control pigs, for example, mean water loss was 6.0 percent, compared with 5.8 percent in pigs that had received 290 mg of vitamin C and 5.2 percent in those receiving 704 mg of vitamin C.

Supplementation also improved color scores in the Iowa State work. The Hunter L* score, which measures the lightness of the meat, was lowest (which is best) for meat from the animals that had received 290 mg of vitamin C before processing. A normal range for these scores is 38 to 55, and a score over 50 is associated with greater risk of PSE pork. In this study, the meat from unsupplemented animals approached that level with a score of 49.5 after nine days of storage ( Figure 2). By comparison, meat from animals fed 290 mg of vitamin C scored 47.4, while those fed 704 mg of vitamin C scored 48.6. The Hunter a* value (P < 0.13), which measures redness, was also best for the meat from the animals receiving 290 mg of vitamin C.

The combination of improvements with vitamin C supplementation is especially notable because the Iowa State researchers reported less impressive results with other glycolytic inhibitors.

These results are in keeping with previous research on vitamin C supplementation and pork quality, as well as similar poultry research. For example, Mourot et al. (1990) reported significant improvements (P < 0.05) in both color and pH when barrows' and gilts' diets were fortified with 500 ppm of dietary vitamin C starting at 77 lbs (35 kg) of body weight and continuing through slaughter.

At 24 hours post-slaughter, the pH of muscle from supplemented barrows was 5.76, compared with only 5.6 for muscle from unsupplemented controls. Color scores, using a reflectometer to measure lightness, showed a 6.6 percent improvement in supplemented barrows and a 13 percent improvement in supplemented gilts compared with the control animals.

Poultry research has also shown improvements in carcass yield with vitamin C supplementation preceding slaughter. Krautman et al. (1990) supplemented broilers with 976 ppm vitamin C in the feed for 24 hours prior to harvest and reported significantly higher hot and chilled carcass yields than in unsupplemented birds.

Because vitamin C is one of the least stable of all the vitamins, it is wise to use a stabilized form of the vitamin such as Rovimix® Stay-C®, especially when the vitamin will not be fed right away. This phosphate ester of the vitamin is stable to heat processing and storage conditions while providing excellent absorption by the animal. With less stable product forms, degradation could compromise results by limiting the amount of vitamin C the animals actually received unless the most stringent management practices were followed.

References:

Krautmann, B.A., et al. 1990. Practical applications of ascorbic acid in poultry. Proc. 2nd Symposium Ascorbic Acid in Domestic Animals, Kartause Ittingen, Switzerland. P. 292.
Kremer, B.T., et al. 1999. The effect of dietary vitamin C on meat quality of pork. J. Anim. Sci. 77(1):46.
Mourot, J., et al. 1990. Effect of a dietary supplement of vitamin C on growth and pig meat quality. Proc. 2nd Symposium Ascorbic Acid in Domestic Animals, Kartause Ittingen, Switzerland. P. 176.
Rajic, I.D. 1971. The effect of ascorbic acid on the prevention of muscle degeneration and pale, soft and exudative meat in swine. Acta. Vet. Beograd. 21:253-265.