Introduction

The increasing demand for pork can be addressed by increasing slaughter weight and exploring alternative feed ingredients in swine diets. Vitamin E (VE) is an antioxidant and plays an important role in improving the oxidative stability of pork. However, interactions among VE isoforms, dietary fat sources, and pork quality are rarely reported. Therefore, the objective of this study was to evaluate the effects of supplementing the vitamin E isoforms alpha-tocopheryl acetate (ATA) and gamma-tocopherol (GT) in combination with corn oil (CO) and tallow (TW) on the color characteristics of fresh pork loins from heavy-weight pigs (>150 kg).

Materials and methods

The experiment was conducted in accordance with protocols approved by the Institutional Animal Care and Use Committee of the University of Kentucky. A total of 72 individually fed pigs (n = 72) were blocked by sire, body weight, and sex and randomly assigned to individual pens. Dietary vitamin E treatments consisted of four levels of ATA (11, 40, 100, and 200 ppm) and two levels of mixed tocopherols, primarily GT (40 and 100 ppm). Pigs were humanely slaughtered at approximately 150 kg live weight at the University of Kentucky USDA-inspected Meat Laboratory. At 24 h postmortem, a 2.54-cm chop was collected from the longissimus thoracis, placed on foam trays, and overwrapped with polyvinyl chloride (PVC) film for instrumental color evaluation. Instrumental color measurements included lightness (L*), redness (a*), yellowness (b*), hue angle (H*), and chroma (C*), which were obtained from three random locations on the light-exposed surface using a HunterLab MiniScan XE colorimeter (HunterLab Associates, Reston, VA) equipped with a 2.54-cm diameter aperture, illuminant A, and a 10° standard observer. Measurements were conducted on days 1, 3, 5, and 7 of retail display under 1,300 lux. Data was analyzed using SAS by least squares analysis of variance with the generalized linear model (GLM) as a randomized complete block design, with the individual pig serving as the experimental unit. Statistical significance was declared at P ≤ 0.05, and tendencies were identified at P ≤ 0.10.

Results

Overall, chops from pigs supplemented with GT tended to exhibit greater lightness (P ≤ 0.10) throughout retail display compared with chops from pigs fed equivalent levels of ATA. Pigs supplemented with TW also tended to have greater lightness (P ≤ 0.10) by the end of the retail display period compared with those fed CO. Supplementation with GT at 40 ppm resulted in greaterlightness (P < 0.05) and hue angle (P < 0.05), along with lower redness (P < 0.05) and chroma (P < 0.05), indicating a paler and less red color compared with 40 ppm ATA. In contrast, supplementation with GT at 100 ppm resulted in lower lightness (P < 0.05) and hue angle (P < 0.05), and greater redness (P < 0.05) and chroma (P < 0.05) during the first 7 d of retail display, indicating a darker and redder color compared with 100 ppm ATA. Chops from pigs fed TW exhibited greater lightness and yellowness values (P < 0.05) during extended retail display compared with chops from pigs fed CO.

Conclusions

These findings demonstrated that supplementation with 40 ppm GT reduced redness and increased lightness of fresh pork. In contrast, supplementation with 100 ppm GT resulted in a darker appearance during the first seven days of retail display compared with ATA. The combined use of GT and TW may be exploited as a pre-harvest strategy to enhance color stability of fresh pork from heavy-weight pigs during retail display.

Acknowledgments

This work was supported by the National Pork Board, Fats and Proteins Research Foundation, and DSM.

Ana Paula Salim, Marlee Kelley, Ding Wang, Gregg Rentfrow, Merlin Lindemann and Surendranath P. Suman are with the Department of Animal and Food Sciences, University of Kentucky, Lexington (e-mail apaulasalim@uky.edu).