Effects of Vitamin C Supplemented Through Drinking Water on Pork Quality
S.J. Pion, E. van Heugten, and M.T. See
North Carolina State University Pork Quality Research from 2002. Supplementing swine with 500 or 1,000 ppm of vitamin C through the drinking water did not result in consistent improvements in measures of pork quality. In fact, supplementation at the 500 mg/L level appeared to have negative effects on pork quality. Consequently, it can be concluded that vitamin C supplementation through the drinking water may not be an effective method towards improving pork quality and decreasing the incidence of PSE pork. Timing of slaughter relative to vitamin C supplementation may be critical in order to observe improvements in pork quality and needs to be studied further.
Introduction
Addressing pork quality issues and concerns is of the highest priority in order to maintain pork as a major protein source in today’s global market. Many nutritional strategies are currently being investigated to improve the quality of pork that is being produced. Supplementation of vitamin E, magnesium, or conjugated linoleic acid (CLA) are just a few of the strategies that are believed to have beneficial effects on pork quality characteristics. Vitamin C has been suggested to improve pH values, color scores, and water holding capacity in pork (Kremer et al., 1999; Mourot et al., 1992; and Cabadaj et al., 1983). Furthermore, vitamin C is water soluble and can therefore easily be supplemented through the drinking water. This may be beneficial as it can be supplemented for short periods of time and at critical time periods pre-slaughter. Economically, vitamin C can be supplemented at a cost of less than $0.15 per pig. Therefore, the following experiment was designed to investigate the effects of vitamin C supplementation through the drinking water on measurements of pork quality and to assess an optimum cost-effective level of supplementation.
Materials and Methods
General Procedure: This experiment was conducted in late spring at the North Carolina State University Swine Educational Unit. Thirty PIC pigs (118.2 kg BW) were housed in individual pens in order to determine individual water and vitamin C intake. Water was supplied to the pigs through individual water systems. Pigs were blocked by sex and weight and assigned to one of three treatments. The treatments consisted either of 0, 500, or 1000 mg/L vitamin C (Lascorbic acid; F. Hoffman-La Roche LTD., Nutley, NJ). Vitamin C treatments were supplemented for a 48-hour period pre-slaughter. Supplementation was started at 7:00 a.m. The supplemented drinking water was changed every 12 hours during the 48-hour supplementation period and fresh vitamin C water was prepared in order to minimize vitamin C degradation during the treatment period. Actual L-ascorbic acid concentrations for treatment 2 were within the range of 612 to 1086 mg/L with an average concentration of 755 mg/L. Actual L-ascorbic acid concentrations for treatment 3 were within the range of 869 to 1562 mg/L with an average concentration of 1105 mg/L. At the end of the 48-hour period water supplementation was ceased and all 30 pigs were transported to a commercial slaughter plant. Once at the slaughter plant, the pigs were randomly selected, stunned and exsanguinated in groups of four. All 30 pigs were stunned by electrical stimulation and exsanguinated between four and five hours after the end of vitamin C supplementation. All pigs were dehaired by scalding, eviscerated, and chilled for 24 hours.
Measurements: Carcass temperature was measured at 1 hour post-slaughter and both initial (1 hour post-slaughter) and ultimate (24 hours post-slaughter) loin pH measurements were determined (Sentron Red-Line LanceFET pH probe; Sentron, Inc., Gig Harbor, WA) on all carcasses. After chilling for 24 hours, the 30 carcasses were processed into primal cuts and three loin chops (longissimus dorsi) were removed from the left loin of each carcass. The first loin chop was cleaned of bone and debris and allowed to bloom for 15 minutes. After fifteen minutes, visual color scoring, Minolta color measurements, and the degree of fluid loss measurements were conducted on each loin chop. The visual color scores were assessed utilizing the National Pork Producer’s Council (NPPC) visual color scoring cards and given a score of 1 through 6. Minolta L*, a*, and b* color values were read, using a Minolta Chromameter 210. The water-holding capacity for each loin chop was assessed utilizing the filter paper method as described by Kauffman (1986). Loin chops were then deboned, placed in cryovac bags, vacuum packaged, heat-sealed, and stored at –20°C for subsequent TBAR analysis (resistance to oxidation). The remaining 60 loin chops (2 from each carcass) were weighed 24 hours post-slaughter and packaged for retail display. All 60 boneless loin chops were displayed in conditions similar to retail display in a refrigerated cooler at temperatures of 1°C. One chop from each of the 30 carcasses was displayed for four days with the remaining 30 chops being displayed for a total of eight days. At the end of the display time, the loin chops were weighed and the degree of fluid that was lost was calculated as a percentage of the original 24 hour post-slaughter chop weight. Furthermore, both visual and Minolta L*, a*, and b* color scores were assessed at the end of the display time as described earlier. Each chop was then placed into a cryovac bag, vacuum packaged, heat-sealed, and stored at –20°C for subsequent TBAR analysis using the method of Salih et al. (1987).
Statistical Analyses: All data were compared by analysis of variance using the general linear model procedure of SAS (1988). The model included replicate, sex, treatment, and the sex by treatment interaction.
Results and Discussion
Water intake from 36 to 48 hours of supplementation was decreased (P<0.05) by supplementing vitamin C at 1000 mg/L (Table 1). However, water intakes for the 48 hours of supplementation were similar across treatments. Average vitamin C intakes for the 48-hr period were 190 mg/hr/pig and 410 mg/hr/pig for the 500 and 1,000 ppm supplemental vitamin C treatments, respectively. No differences (P>0.10) in post-mortem carcass temperature were observed between the treatments (Table 2). Furthermore, both initial and ultimate post-mortem pH values were similar across treatments (Table 2).
Table 1. Differences in water consumption of pigs supplemented with vitamin C through the drinking water 48 hours pre-slaughter1
| Level of Vitamin C (mg/L) | 0 | 500 | 1000 |
|---|---|---|---|
| 0 – 12 hrs | 0.67 ± 0.04 | 0.66 ± 0.05 | 0.72 ± 0.04 |
| 12 – 24 hrs | 0.15 ± 0.03 | 0.17 ± 0.03 | 0.17 ± 0.03 |
| 24 – 36 hrs | 0.68 ± 0.04 | 0.54 ± 0.04 | 0.62 ± 0.04 |
| 36 – 48 hrs | 0.20 ± 0.02 | 0.14 ± 0.02 | 0.09 ± 0.02a |
| Total 48 hrs | 0.42 ± 0.02 | 0.38 ± 0.02 | 0.40 ± 0.02 |
1Each mean is accompanied by its standard error a1000 mg/L vs. 0 mg/L differ (P<0.05)
Table 2. The effect of vitamin C supplementation through the drinking water preslaughter on carcass temperature 1 hr post-mortem and muscle pH 1 hr (pHi) and 24 hrs (pHu)post-mortem1
| Vitamin C Level (mg/L) | 0 | 500 | 1000 |
|---|---|---|---|
| Temperature (°C) | 24.0 ± 1.0 | 24.6 ± 1.0 | 23.0 ± 1.0 |
| pHi | 6.0 ± 0.07 | 5.9 ± 0.07 | 6.0 ± 0.07 |
| pHu | 5.4 ± 0.02 | 5.4 ± 0.02 | 5.5 ± 0.02 |
1Each mean is accompanied by its standard error
Minolta L* color scores (Table 3) measured on day 4 of retail display were greater (P<0.05) in loin chops from pigs supplemented with 500 mg/L vitamin C compared to treatments 1 and 3. No differences in Minolta L* color scores were observed between treatments for chops displayed for 0 or 8 days. Minolta a* color scores (Table 3) at day 0 were greater (P<0.10) in loin chops from pigs supplemented at the 500 mg/L level in relation to treatments 1 and 3 with no further differences observed at day 4 and 8 of retail display Vitamin C supplementation at the 500 mg/L level resulted in loin chops having greater Minolta b* color scores at day 0 (P<0.05), 4 (P<0.10), and 8 (P<0.05) of retail display when compared to treatments 1 and 3 (Table 3). However, no differences in visual color scores were observed between the three treatments (Table 3).
Table 3. The effects of supplementing finishing swine with vitamin C in the drinking water pre-slaughter on Minolta and Visual meat color scores of loin chops displayed for 0, 4, or 8 days1
| Vitamin C Level (mg/L) | 0 | 500 | 1000 |
|---|---|---|---|
| Minolta L* | |||
| d0 | 51.1 ± 1.2 | 54.4 ± 1.2 | 50.9 ± 1.2 |
| d4ab | 53.2 ± 0.7 | 55.9 ± 0.7 | 53.1 ± 0.7 |
| d8 | 53.1 ± 0.9 | 55.8 ± 0.9 | 53.6 ± 0.9 |
| Minolta a* | |||
| d0ad | 8.1 ± 0.4 | 9.4 ± 0.4 | 8.2 ± 0.4 |
| d4 | 8.4 ± 0.2 | 9.0 ± 0.2 | 8.6 ± 0.2 |
| d8 | 5.8 ± 0.2 | 6.03 ± 0.2 | 6.0 ± 0.2 |
| Minolta b* | |||
| d0ab | 6.1 ± 0.4 | 7.8 ± 0.4 | 6.0 ± 0.4 |
| d4bc | 8.2 ± 0.2 | 8.9 ± 0.2 | 8.0 ± 0.2 |
| d8ab | 7.3 ± 0.3 | 8.59 ± 0.3 | 7.3 ± 0.3 |
| Visual | |||
| d0 | 2.8 ± 0.2 | 2.4 ± 0.2 | 2.9 ± 0.2 |
| d4 | 2.8 ± 0.1 | 2.6 ± 0.1 | 2.9 ± 0.1 |
| d8 | 2.5 ± 0.2 | 1.9 ± 0.2 | 2.4 ± 0.2 |
1Each mean is accompanied by its standard error a500 mg/L vs. 0 mg/L differ at P<0.05 b500 mg/L vs. 1000 mg/L differ at P<0.05 c500 mg/L vs. 0 mg/L differ at P<0.10 d500 mg/L vs. 0 mg/L differ at P<0.10
The degree of fluid loss from day 0 chops (Table 4) was greater in loin chops from pigs that were supplemented with 500 mg/L vitamin C when compared to treatments 1 and 3. Furthermore, vitamin C supplemented at 500 mg/L further resulted in greater fluid losses at both 4 (P<0.05) and 8 (P<0.10) days of retail display compared to treatments 1 and 3 (Table 4). Vitamin C supplementation had no effect (P>0.10) on oxidative stability (Table 5).
Table 4. The effect of vitamin C supplemented through the drinking water pre-slaughter on degrees of fluid loss in loin chops after 0, 4, or 8 days of display1
| Vitamin C Level (mg/L) | 0 | 500 | 1000 |
|---|---|---|---|
| Day 0, mgb | 125.4 ± 14.4 | 154.9 ± 14.4 | 107.2 ± 14.4 |
| Day 4, %ac | 2.3 ± 0.3 | 3.9 ± 0.3 | 2.9 ± 0.3 |
| Day 8, %a | 4.3 ± 0.4 | 6.0 ± 0.4 | 5.4 ± 0.4 |
1Each mean is accompanied by its standard error a500 mg/L vs. 0 mg/L differ at P<0.05 b500 mg/L vs 1000 mg/L differ at P<0.05 c500 mg/L vs. 1000 mg/L differ at P<0.10
Table 5.The effect of vitamin C supplementation through the drinking water pre-slaughter on measures of oxidative stability (TBARS, mg/kg MDA) at 0, 4, and 8 days of retail display1
| Vitamin C Level (mg/L) | 0 | 500 | 1000 |
|---|---|---|---|
| 0 Days of Display | 0.10 ± 0.01 | 0.11 ± 0.01 | 0.12 ± 0.01 |
| 4 Days of Display | 0.11 ± 0.01 | 0.11 ± 0.01 | 0.12 ± 0.01 |
| 8 Days of Display | 0.15 ± 0.009 | 0.13 ± 0.01 | 0.14 ± 0.009 |
1Each mean is accompanied by its standard error
Results obtained in this study indicate that supplementing swine with 500 and 1000 mg/L vitamin C in the drinking water did not affect pH values, visual color scores, or oxidative stability. These results are in contrast with those reported by Mourot et al. (1990 and 1992) and Kremer et al. (1999). Kremer et al. (1999) observed increases in muscle pH, decreased L* color scores, and decreased water loss when pigs were supplemented with 738 and 2348 mg/kg of vitamin C for 4 hours prior to stunning. In addition, Mourot et al. (1990, 1992) observed similar improvements in measures of pork quality (pH and color) when supplementing finishing swine with 250 mg vitamin C per kg feed from 35 kg to 100 kg BW. On the other hand, several reports have documented no effect (Rajic, 1971) or even negative effects of vitamin C supplementation (Rajic, 1971; Cabadaj et al., 1983). Although vitamin C can regenerate vitamin E, which in turn could decrease lipid oxidation in meat (Monahan et al., 1992; Monahan et al., 1993; and Cannon et al., 1996), we did not observe an effect of vitamin C supplementation on oxidative stability. This observation is in agreement with Tsai et al. (1978), who reported that supplementing swine with 2000 ppm ascorbic acid in the feed from 10 kg to 91 kg BW failed to improve the oxidative stability of pork muscle.
The failure of vitamin C to improve pork quality in this experiment may be related to low water consumption during the 12 hrs preceding shipment to the slaughter facility and the 4 hr time period prior to slaughter. Ascobic acid has been hypothesized to affect pork quality through its metabolite oxalate, which inhibits glycolysis and lactic acid production in the muscle postmortem (Mourot et al., 1990). The lack of an effect of vitamin C on pork quality may have been due to the relatively rapid turnover of ascorbic acid and its metabolites and the extended period in which no vitamin C was consumed. This is consistent with the observation that ascorbic acid and oxalate concentrations in the plasma and muscle of pigs in this experiment were not affected by the supplementation of 500 or 1,000 ppm of vitamin C (data not shown).
Implications
On-farm supplemention of vitamin C in the water of finishing pigs did not appear to be an effective strategy to improve pork quality. Due to the rapid turnover of vitamin C and its metabolites, supplementation immediately prior to slaughter may be necessary to detect any positive effects and needs to be further evaluated.
Literature Cited
Cabadaj, R., J. Pleva, and P. Mala. 1983. Vitamin C in the prevention of PSE and DFD meat. Folia Veter. 27:81-87.
Cannon, J.E., J.B. Morgan, G.R. Schmidt, J.D. Tatum, J.N. Sofos, G.C. Smith, R.J. Delmore, and S.N. Williams. 1996. Growth and fresh meat quality characteristics of pigs supplemented with Vitamin E. J. Anim. Sci. 74:98.
Kauffman, R.G. 1986. The use of filter paper to estimate drip loss of porcine musculature. Meat Science. 18:191-200.
Kremer, B.T., T.S. Stahly, and R.C. Ewan. 1999. The effect of dietary vitamin C on meat quality of pork. J. Anim. Sci. 77(Suppl. 1) p. 46.
Monahan, F.J., J.I. Gray, A. Asghar, A. Haug, B. Shi, and D.J. Buckley. 1993. Effect of dietary lipid and vitamin E supplementation on free radical production and lipid oxidation in porcine muscle microsomal fractions. Food Chem. 46:1.
Monahan, F.J., J.I. Gray, A.M. Booren, E.R. Miller, D.J. Buckley, P.A. Morrissey, and E.A. Gomaa. 1992. Influence of dietary treatment on lipid and cholesterol oxidation in pork. J. Agric. Food Chem. 40:1310.
Mourot, J., A. Aumaitre, and P. Wallet. 1990. Effect of a dietary supplement of vitamin C on growth and pig meat quality. In: Proc. Ascorbic Acid in Domestic Animals. 2nd Symposium. Kartause Ittingen, Switzerland.
Mourot, J., P. Peiniau, A. Aumaitre, P. Chevillon. 1992. Effect of dietary vitamin C supplementation on growth performance and meat quality in Large White or Large White x Pietrain pigs. Journees Rech. Porcine En France. 24:55-64.
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.
Salih, A.M., D.M. Smith, J.F. Price, and L.E. Dawson. 1987. Modified extraction 2-thiobarbituric acid method for measuring lipid oxidation in poultry. Poult. Sci. 66:1483-1488.
SAS. 1988. SAS User’s Guide: Statistics. SAS Inst. Inc., Cary, NC.
Tsai, T.C., G.H. Wellington, and W.G. Pond. 1978. Improvement in the oxidative stability of pork by dietary supplementation of swine rations. J. Food Sci. 43:193-196.