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The oxidation of alpha-tocopherol (TH) in beef was analyzed using a stable isotope dilution capillary gas chromatography-mass spectrometry assay. TH decreased while alpha-tocopherolquinone (TQ) and 2,3-epoxy-alpha-tocopherolquinone (TQE(2)) increased in ground longissimus lumborum (LL) and psoas major (PM) muscles during storage (P < 0.10). In LL steaks, the relative concentrations of TH decreased and TQ and TQE(2) increased in surface samples; changes were less dramatic in deep samples. Deuterated alpha-tocopherolhydroquinone (THQ) standard was not recovered and endogenous THQ was not detected in meat; THQ was measurable in microsomes isolated from PM and incubated in the presence of 2, 2'-azobis(2-amidopropane)HCl (ABAP) or myoglobin. ABAP-challenged microsomes yielded a tocopherol product profile which favored 5, 6-epoxy-alpha-tocopherolquinone (TQE(1)) and TQE(2), while the use of myoglobin as prooxidant resulted in a higher proportion of TQ and THQ. Results demonstrated that concentrations of TH decreased and TQ and TQE(2) increased in meat during storage and are consistent with the peroxy-radical scavenging function of tocopherol.

Hereford-Angus crossbred heifers were fed a cottonseed meal-based diet containing gossypol (14 mg free gossypol x kg body wt(-1) x d(-1); CSM), a soybean meal-based diet (SBM), or alpha-tocopherol-supplemented diets (4,036 IU vitamin E x heifer(-1) x d(-1) for 90 d; CSM+E and SBM+E). The effects of diet on color stability and aerobic metmyoglobin reducing ability of beef longissimus lumborum (LL) and psoas major (PM) were evaluated. The CSM containing gossypol did not affect alpha-tocopherol concentration, a* value, or hue angle value of beef muscles obtained from control or vitamin E-supplemented cattle compared to their SBM counterparts. Vitamin E supplementation increased endogenous alpha-tocopherol concentrations and color stability in LL and PM muscles compared with controls from either diet (P < .05). In the aerobic metmyoglobin reducing ability study, LL and PM muscles were stored in 1% O2:99% N2 (a pigment-oxidizing atmosphere) for 48 h and subsequently stored aerobically for an additional 48 h. Within the LL, alpha-tocopherol supplementation delayed metmyoglobin formation in LL exposed to 1% O2 (P < .05). Within the PM, no differences in metmyoglobin formation were found between controls and vitamin E treatments in SBM or CSM diets. Relative aerobic metmyoglobin reduction was the same (P > .05) in LL and PM muscles within SBM or CSM diets for control and vitamin E treatments. Alpha-tocopherol did not seem to affect metmyoglobin aerobic reducing ability in LL and PM muscles.

Dietary supplementation of livestock with vitamin E results in improved quality of meat subsequently obtained from these animals. The effect is especially noteworthy in cattle, in which the primary effects are delayed discoloration and lipid oxidation. A threshold level of alpha-tocopherol in muscle ensures a detectable effect; dietary strategies for attaining this threshold must consider tocopherol status of cattle arriving at the feedyard and duration and level of supplementation. The alpha-tocopherol concentration in muscle must be determined before proper interpretation of experimental results can be made. Muscles vary in their color stability, and this relative difference is not changed by vitamin E supplementation. Several in vitro models have been used to characterize the interaction between alpha-tocopherol, lipid oxidation, and oxymyoglobin oxidation. Alpha-tocopherol seems to exert its color-stabilizing effect by indirectly delaying oxymyoglobin oxidation via direct inhibition of lipid oxidation. However, recent results demonstrating a protective effect of alpha-tocopherol toward oxymyoglobin in low-oxygen atmospheres indicate that additional mechanisms may exist. A better understanding of the fundamental bases for protection of water-soluble myoglobin by lipid-soluble alpha-tocopherol is needed to optimize this beneficial effect.

Vitamins E and C are important antioxidants in animals. Their antemortem activity continues to function in postmortem muscle (meat), where they have a critical role in maintaining quality in the food product. Dietary supplementation of vitamin E, and intravenous infusion of vitamin C immediately before harvest, are efficacious techniques for increasing the concentration of these vitamins in beef skeletal muscle. Meat with elevated levels of either and probably both of these antioxidant vitamins possesses greater stability of oxymyoglobin and lipid, which results in less discoloration and rancidity, respectively. A model is proposed for the redox relationships between myoglobin and phospholipid in beef with emphasis on vitamins E and C. Antemortem nutritional intervention appears to be a promising approach for improving the quality of fresh meat products subsequently obtained from livestock.

Aldehyde lipid oxidation products and protein:aldehyde adducts were detected in vitro and in stored ground beef. Propional, pentenal, hexanal and 4-hydroxynonenal (4-HNE) were the primary aldehydes formed during lipid oxidation. The 4-HNE concentration was higher in 1,2-dilinoleoyl-phosphatidylcholine liposomes (PCL) exposed to Mb than to AAPH (P < 0.05). Elevated concentrations of α-tocopherol (α-Toc) in PCL or microsomes reduced the production of aldehyde lipid oxidation products compared to controls (P < 0.05). Proteins adducted by 4-HNE, malondialdehyde, and hexenal, heptenal, octenal and nonenal (C6-C9enal) were detected in PCL, microsomes and beef by indirect ELISA. These results demonstrate that aldehydes produced during lipid oxidation can form adducts with proteins and that this may have implications for protein stability and functionality. [ABSTRACT FROM AUTHOR]

BSTRACT Effect of vitamin E (Vit E), vitamin C (Vit C) and their combination (Vit E + C) on pigment and lipid stability in raw ground beef was studied during 7 days illuminated display at 4°C. Oxidations of pigment and lipid were greatest in controls. Vit E treatment showed moderate pigment and lipid oxidation, and Vit C treatment showed low pigment and lipid oxidation. Vit E+C treatment resulted in the lowest pigment and lipid oxidation. [ABSTRACT FROM AUTHOR]

BSTRACT Pigment and lipid oxidation was investigated in fresh ground sirloin from control and vitamin E-supplemented (370 I.U./head/day) Holstein steers. Alpha-tocopherol levels were higher (P<0.05) in muscle from supplemented animals than from controls. During 6 days storage at 4°C, metmyoglobin accumulation and lipid oxidation (TBA) were greater (P<0.05) in beef from control versus supplemented animals. TBA value and % metmyoglobin were highly correlated in the control (r = 0.91) and supplemented (r = 0.72) groups. TBA values of cooked sirloin slices subsequently stored for 2 days at 4°C, and for frozen ground sirloin patties stored at -18°C for 1.5 and 3 months, were lower (P<0.05) in beef from supplemented animals than from controls. Meat which contained in excess of ca. 0.3 mg α-tocopherol/100 g tissue displayed the least oxidation of both pigments and lipids. [ABSTRACT FROM AUTHOR]

Colorimetric measurements were recorded for sirloin steaks from control and vitamin E-supplemented (370 I.U./animal/day) Holstein steers. Chroma and Hunter 'a' values of steaks from the supplemented group were significantly greater (P&0.01) on days 2, 4, 6, and 8 of 4°C storage. Color difference (ΔΕ) between the two treatment groups increased from days 0 to 6 and decreased between days 6 and 8. [ABSTRACT FROM AUTHOR]

Abstract: This study was carried out to determine an effective combination of chelators, reductants and free radical scavengers for enhancing color stability and minimizing lipid oxidation in muscle foods fortified with n −3 fatty acids. Chelators (sodium tripolyphosphate, STPP; sodium citrate, CIT), reductants (sodium erythorbate, ERY) and radical scavengers (butylhydroxyanisole, BHA; mixed tocopherols from two different sources, 30 or 95TOC; rosemary extract, ROSE) were incorporated in various combinations into ground beef (15% fat) with or without n −3 oil fortification (n =8). Individually, STPP and CIT had no significant effect on a* values except day 4, but showed higher a* values when combined with ERY (STPP+ERY and CIT+ERY) (P &#60;0.05). CIT had lower hue angle values than STPP on days 4 and 6, but CIT+ERY showed more discoloration than STPP+ERY (P &#60;0.05). CIT+ERY showed less lipid oxidation than CIT alone (P &#60;0.05), whereas there was no difference between STPP and STPP+ERY. CIT+ERY+ROSE demonstrated higher a* values than CIT+ERY+95TOC on days 4 and 6 (P &#60;0.05); there was no difference between ROSE and 95TOC groups when n −3 oil was incorporated into ground beef patties (P >0.05). The combination of ROSE and ERY appeared to be effective in slowing the decline of a* values. All antioxidant combinations were effective at delaying lipid oxidation when compared to CON or n −3. A combination of CIT, ERY and ROSE was most effective for stabilizing color and delaying lipid oxidation. [Copyright &y& Elsevier]