Pasture and Grain Finishing Affect the Color Stability of Beef M.C. LANARI, M. BREWSTER, A. YANG, AND R.K. TUME

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1 JFS: Pasture and Grain Finishing Affect the Color Stability of Beef M.C. LANARI, M. BREWSTER, A. YANG, AND R.K. TUME ABSTRACT: We determined the effect of pasture feeding (P0) or sorghum feeding with 2500 IU/head/d; (G2500) or without (G0) vitamin E supplementation on the color stability of gluteus medius (GM), longissimus lumborum (LL) and semimembranosus (SM). Diets did not affect the total pigment concentration of the muscle. Color stabilities were G2500 > P0 > G0 for fresh GM and SM and G2500 > G0 > P0 for fresh LL. Color stabilities of aged beef from the P0 and G2500 treatments were similar and higher than those from unsupplemented animals. Color stability of minced beef ranked as: P0 aged > G0 and G2500 fresh > P0 fresh > G0 and G2500 aged. Keywords: beef color, pasture and grain finishing, vitamin E, a-tocopherol Introduction COLOR PERCEPTION PLAYS A MAJOR ROLE IN THE EVALUATION of meat quality as consumers use color as an indicator of freshness. In most countries beef production is based on pasture feeding. Although this system offers many animal welfare and economic advantages compared with feedlot finishing, some consumers consider pasture-fed beef inferior, as it is sometimes darker than meat from grain-fed cattle (Bidner and others 1981). Information regarding the influence of pasture on beef color and color stability is scarce, often contradictory and mostly based on subjective evaluation. Several authors (Reagan and others 1977; Crouse and Seideman 1984; Crouse and others 1984; Therkildsen and others 1998; Vestergaard and others 2000) reported that, in comparison with beef from grain-fed cattle, pasture feeding produced darker meat. However, in all these studies, the pasture-fed steers were 10- to 12-mo older. As meat becomes darker with an increase in animal age (Renerre 1990), the reported effect of the finishing system was confounded with that of animal age. Reagan and others (1977) concluded that beef from pasture-fed steers was less color-stable than that from grain-fed cattle. In contrast, Thomas (1981) showed that beef from pasturefed steers had the least color change during retail display. Reasons for these disparities may include variations in animal age and carcass weight between both production systems, a lack of objective color measurements and not considering the fundamental role played by the antioxidants and the fats of the diet on the oxidative status and color stability of the muscle. Inclusion of antioxidants and/or fats into the animal diet can be an effective way of altering the balance between anti- and pro-oxidant compounds and, hence, the color stability of the muscle. Several reports (Liu and others 1995; Houben and others 1998; Mercier and others 1998) have shown that dietary vitamin E significantly improved the lipid and color stability of grain-fed beef, pork, poultry, and fish. In contrast, feeding cattle with highly unsaturated fats like fish oil or linseed oil, which increases the content of polyunsaturated fatty acids (PUFAS) in the muscle, resulted in reduced color and lipid stability (Mandell and others 1997; Vatansever and others 1998). Cereals, grains, and green forages can modify the fatty acid composition of beef phospholipids (Larick and others 1989; Enser and others 1998; Srinivasan and others 1998). Larick and others (1989) and Enser and others (1998) showed that PUFA content was higher in grass-fed than in grain-fed beef. As a result of the high content of -tocopherol in good quality pasture (Jukola and others 1996), grazing animals on such pasture will result in elevated concentrations of -tocopherol in muscles, similar to those found in meat of grain-fed steers supplemented with 2500 IU vitamin E (Lanari and others 1999). However, the effectiveness of -tocopherol, or any other antioxidant, on the color stability of pasture-fed meat may be compromised by a more oxidative phospholipid fraction. Recently, Lanari and others (1999) showed that the nutritional background (pasture or grain) produced significant alterations to the color and lipid stability of beef. However, because of differences in carcass weight between the dietary treatments used in that study, it was not possible to determine the effect of diet per se on color stability as it was confounded with differences in the chilling rate (Lanari and others 1999). Pasture feeding is the most common production system in most countries, therefore, determining the effect of pasture finishing compared with grain-feeding with and without vitamin E supplementation on the color stability of beef will provide useful information to those countries where the beef production system is pasture based. This experiment was designed to analyze the relationship between nutritional background (pasture and grain finishing) and dietary vitamin E on the color stability of fresh and aged primal cuts and minced beef. Materials and Methods Animals and Diets Twenty-one Hereford cross steers (approximately 300-kg body weight) were randomly divided into 3 groups of 7 animals. For 110 d prior to slaughter (August to November), each group was fed freely one of the following diets. (a) pasture-fed (P0) with predominantly Rhodes pasture (Chloris gayana L) (b) sorghum-based feedlot ration supplemented with 0 (G0) or 2500 (G2500) IU/head/d of all-rac -tocopheryl acetate (Vitamin E, Hoffman-La Roche Inc., Goodna, QLD Australia). To determine the -tocopherol and -carotene contents in grass during the feeding period, samples of Rhodes pasture were cut monthly. The average concentrations in Rhodes pasture over the feeding trial were 116 and 270 mg/g respectively. The daily vitamin E intake of the pasture-fed cattle was estimated consid Institute of Food Technologists Vol. 67, Nr. 7, 2002 JOURNAL OF FOOD SCIENCE 2467

2 ering a pasture consumption of 2.5% of the animal body weight. Vitamin E intake for the P0 and G0 treatments was calculated to be 3480 and 45 IU/head/d respectively, which corresponded to the vitamin E consumption from the basal ingredients. Therefore, the estimated consumption by the supplemented steers (G2500) was 2545 IU/head/d. The cattle were slaughtered under commercial conditions and at 24 h postmortem, the longissimus lumborum (LL), semimembranosus (SM) and the gluteus medius (GM) muscles were removed, vacuum-packed, and transported to the laboratory. Carcass chilling rates were determined by monitoring the temperature of the LL muscle between the 12th and 13th rib during the first 24 h postmortem. Color Stability At 48-h postmortem, cores (15-mm thick 35-mm dia.) were cut from each muscle (GM, LL, and SM) and wrapped in oxygenpermeable fresh meat PVC film (O 2 permeability = cm 3 /m 2 /24 h at 23 C) and either (a) kept in the dark at 4 C for 14 d (aerobic storage) or (b) cores from the LL and SM wrapped in PVC film were vacuum-packed and aged for 30 d at 1 C. Samples were then removed from the vacuum pack and stored for 10 d at 4 C in the dark. The color stability of ground meat was determined in LL that had been stored under vacuum at 1 C for 6 or 37 d. At each time postmortem, the LL was ground and 100-g samples were overwrapped with fresh meat film (PVC) and stored at 4 C for 8 d in the dark. Analysis -Tocopherol concentration in the feeds and muscles was determined using the method of Liu and others (1996b). -Carotene concentration was determined according to Yang and others (1992). Total pigment concentration of the muscle was estimated using the extraction method of van Laack and others (1996) on duplicate samples from each muscle/treatment combination. Meat color was daily measured on triplicate samples with a Minolta CR-200 Chroma Meter (Minolta, Osaka, Japan). Color was expressed by CIE L* (lightness), a* (redness), b* (yellowness), saturation index (SI) and hue angle (HA). SI, a measure of color intensity, was computed as: SI = (a* 2 +b* 2 ) 0.5 (Minolta 1993) HA represents the psychometric hue and was calculated as: HA = tan 1 (b/a) (Minolta 1993) An increase in HA and a reduction in SI or a* indicates a higher degree of meat browning (Liu and others 1996a), Statistical analysis Treatments were compared by analysis of variance using the Proc Mixed procedure of SAS (1998). For comparison pertaining to diet, muscle type, and storage time, a split-plot analysis was used to account for repeated measurements. The 3 dietary treatments, P0, G0, and G2500, were considered as the main plot, while muscle type and its interactions with the treatments previously named were analyzed as subplot variables. The effects of storage time and its interactions were analyzed as sub-subplot variables. Carcass weight and fat thickness can affect meat color by altering the rates at which the muscles cool. Thus, for all the Table 1 a-tocopherol concentrations (µg/g tissue) in muscle from pasture- and grain-fed cattle with or without vitamin E supplement (n = 7) Pasture Grain Muscle Control Control Supplemented GM 6.5 a 2.4 b 5.2 a LL 4.4 a 1.8 b 4.8 a SM 4.5 a 2.6 b 6.4 a 1 Means within the same row with different superscripts are statistically different (P < 0.05). color parameters, these factors were considered as covariates. Differences across means were determined using least square means. The variation in a* over time was fitted by nonlinear regression (SAS 1998). Results and Discussion a-tocopherol content in muscle Table 1 presents the effect of the dietary treatments on the tocopherol concentrations of the 3 muscles. In accordance with our previous work (Lanari and others 1999), grazing cattle on Rhodes grass containing 116 mg/g of natural vitamin E resulted in -tocopherol concentrations in muscle similar to those obtained after supplementing with 2545 IU/head/d of all-rac -tocopheryl acetate for 110 d. As expected from previous publications (Lanari and others 1996; Liu and others 1996a), supplementing grain-fed cattle with 2545 IU/head/ increased (P < 0.05) the -tocopherol concentration of all the muscles. Effect of pasture- and grain-feeding on the color stability of primal cuts Renerre & Bonhomme (1991) showed that an increase in the chilling rate significantly reduced redness in beef. Mallikarjunan and Mittal (1994) reported that variations in carcass weight and fat thickness might alter significantly the carcass chilling rate and consequently meat color. In the current study, the carcasses from the pasture-fed cattle chilled considerably faster than those from the grain-fed animals (data not shown); the time necessary to reach 13.5 C was 4 h longer in the grain-fed than in the pasture-fed carcasses. Therefore, carcass weight and fat thickness effects on meat color were assessed by covariance analysis. The average carcass weights were (P0), (G0), and kg (G2500), while the subcutaneous fat depth (measured at the 8 th rib site) were: 5.0, 12.6, and 10.3 mm. Although carcass weight and fat thickness of the P0 cattle were significantly lower (P < 0.05) than those from the grain-fed cattle, their effects on all the color parameters were not significant (P > 0.30). Within each muscle type, the effect of supplementation and nutritional background did not influence the L* or b* values (P > 0.60) of fresh or aged beef during aerobic storage at 4 C (data not shown). The average L* values across treatments and d were (GM), (LL), and (SM) for fresh meat and and for aged LL and SM respectively. b* values for fresh beef were: (GM), 9.50 (LL), and (SM). Aging did not affect (P > 0.15) yellowness, the average b* values across treatments for the LL and SM were 8.61 and 10.24, respectively. Variations of a* values over time for the different muscle X treatment combinations (Figure 1) showed that, in accordance with previous publications (Schaefer and others 1996, Liu and others 1996a), dietary vitamin E delayed (P < 0.05) the loss of redness (a*) in all the fresh grain-fed muscles during 14-d aero JOURNAL OF FOOD SCIENCE Vol. 67, Nr. 5, 2002

3 bic storage. There was a significant muscle X treatment interaction. From day 0 to 5, a* values of GM and SM (Figure 1a and 1c) were: G2500 > G0 = P0 (P < 0.01). From day 6 to 14, a* for P0 and G2500 GM were similar (P > 0.65) and significantly higher (P < 0.05) than for G0 GM. For the same period, no treatment effect (P > 0.25) was detected in the redness values of the SM. In accordance with a previous work (Lanari and others 1999), between days 0 and 7, no significant effect of supplementation (P > 0.46) was detected on the a* values of the LL of grain-fed cattle. However, from day 8 to 14, supplementation improved (P < 0.05) color stability. The effect of the nutritional background on the color and color stability of the LL did not follow the same pattern as in the other muscles. During the 14-d storage, grain feeding with and without supplementation improved the color and color stability of the LL compared to pasture feeding (P < 0.003). Reagan and others (1977), using subjective measurements, reported similar results. Analysis of the SI (data not shown) response to the different treatments resulted in similar conclusions. Figure 2 shows the effect of the different dietary treatments on HA values during 14 d aerobic storage. Between day 0 and 3, the dietary treatments did not influence (P > 0.60) the color stability of the 3 muscles. From day 4 to 14, pasture feeding resulted in significantly lower (P < 0.02) HA values for the GM (Figure 2a), the treatment effect ranked: P0 = G2500 < G0. The overall mean values for that period were 30.6, 32.1, and 35.2 for the P0, G2500, and G0 treatments, respectively. Figure 2b shows the effect of the nutritional background and vitamin E supplementation on the LL. The LL from pasture-fed cattle had the highest HA values Figure 1 Effect of pasture and grain feeding with vitamin E supplementation on a* of fresh GM (a) and fresh and aged LL (b) and SM (c). The lines represent a* values predicted by the kinetic model. Figure 2 Effect of pasture and grain-feeding with vitamin E supplementation on HA of fresh GM (a) and fresh and aged LL (b) and SM (c) Vol. 67, Nr. 5, 2002 JOURNAL OF FOOD SCIENCE 2469

4 Table 2 Rate constants (k) and initial and asymptote values of a* for fresh and aged primal cuts (n = 7) Muscle Treatment Aging a RM b C c 1 k d (d 1 ) C e f GM P (± 1.16) 0.43 (± 0.05) (± 0.24) GM G (± 0.81) 0.21 (± 0.03) (± 0.59) GM G (± 0.85) 0.24 (± 0.03) (± 0.59) LL P (± 0.46) 0.23 (± 0.04) (± 0.34) LL G (± 0.28) (± 0.1 x 10 2 ) LL G (± 0.66) 0.18 (± 0.02 x 10 2 ) (± 0.40) SM P (± 0.74) 0.24 (± 0.03) (± 0.49) SM G (± 0.85) 0.16 (± 0.03) (±1.10) SM G (± 0.48) 0.04 (± 0.2 x10 2 ) LL P (± 0.27) 0.01 (± 0.22 x 10 2 ) LL G (± 0.37) 0.04 (± 0.30 x 10 2 ) LL G (± 0.34) 0.02 (± 0.20 x 10 2 ) SM P (± 0.44) 0.05 (± 0.5 x 10 2 ) SM G (± 0.36) 0.06 (± 0.3 x 10 2 ) SM G (± 0.52) 0.05 (± 0.4 x 10 2 ) a aging time (d); b Regression model, 2 = Eq. 2; 3 = Eq. 3; c amplitude (±SE); d rate constant; e asymptote value (P < 0.002) while no significant difference (P > 0.91) in HA values was detected between G0 and G2500. For the SM (Figure 2c), the HA variation over time was independent (P > 0.60) of the treatments. For all the treatment/muscle combinations, HA results were consistent with the conclusions obtained from the a* and SI data. Figures 1b and 1c show a* variation over time for 30 d aged LL and SM. From day 0 to 4 there was no significant difference (P > 0.40) between treatments in the LL or SM samples. However, from day 5 to 10, the color stability of pasture and supplemented grainfed LL was similar (P > 0.35). Both pasture feeding and vitamin E supplementation improved (P < 0.05) color stability; a* values of the pasture and supplemented grain-fed LL were higher (P < 0.05) than those of the control grain-fed LL. Aging for 30 d did not alter (P > 0.40) a* values of pasture-fed LL (Figure 1b). In contrast, a* values in grain-fed aged LL were lower (P < 0.01) than in their fresh counterparts. At d 10, a* values for fresh and aged P0 samples were 18.3 while for grain-fed meat, a* values were 22.1 (G2500 fresh), 20.8 (G0 fresh), 17.8 (G2500 aged) and 15.4 (G0 aged). Comparison across muscle type showed that color response to aging in P0 LL and SM differed. In contrast with the LL, aging of SM significantly diminished (P < 0.01) a* levels. At day 10, a* values of fresh and aged P0 SM were 18.1 and 13.8 respectively. The response of the grain-fed SM to aging was similar to that observed in grain-fed LL. At day 10, a* values were (G0 fresh), (G2500 fresh), (G0 aged), and (G2500 aged). An analysis of the treatment effects on SI (data not shown) and HA (Figure 2b and 2c) resulted in similar conclusions. Mathematical description Lanari and others (1996) showed that the oxidation of red oxymyoglobin to form brown metmyoglobin in refrigerated beef followed first-order kinetics. Since color coordinates depend on the relative concentrations of the myoglobin forms, we can assume that the variations of a*, SI or HA with time will also follow the same kinetics. Based on these considerations, the following expressions were derived: dc/dt = - k * C (1) C = C 1 * e ( k * t) + C f (2) C represents a*, SI or HA at time t, k (d 1 ) the rate constant, C f is the asymptotic value of C and C 1 is the difference between the initial and asymptotic values of C. When the reaction rate was slow enough so that the asymptotic levels were not attained, C f = 0. Under these conditions, the integrated solution is: C = C 1 * e ( k * t) C (3) The 3 model parameters, C 1, k, and C f, were estimated using nonlinear regression analysis (SAS 1998). Experimental data of a*, SI, and HA obtained from fresh and aged meat were satisfactorily fitted by either Equation 2 or 3. Selection of the best fitting equation was based on the following criteria: (a) independent parameters; (b) minimum error mean square and (c) homogeneous distribution of residuals against storage time. The type of regression equation and the rate constants, amplitude and asymptote values for a* are given in Table 2. Storage life of primal cuts Subjective assessment of meat color performed in this laboratory indicated that a*= 18 could be considered as the limit of acceptability for fresh beef. Combining this result with Equations 2 or 3, we calculated the color storage life for each treatment combination (Table 3). Color storage life ranges were determined for the storage time when the 95% confidence interval of the regression line included a* = 18. The color storage lives of the GM and LL from control and supplemented grain-fed steers determined in this study were similar or longer than those reported by Lanari and others (1999) working under similar conditions. With the parameters of the regression models fitted for SI and HA and the color storage life values previously obtained (Table 3), we determined the tolerance limits for SI and HA. SI values less than 20 and HA greater than 25 are equivalent to a limit value of 18 for a*. A comparison between the P0 and G0 treatments (Table 2) in fresh beef showed that pasture finishing increased the rate constants in all muscles when compared with grain feeding, suggest JOURNAL OF FOOD SCIENCE Vol. 67, Nr. 5, 2002

5 Table 3 Calculated mean values and 95% confidence intervals (CI) of the calculated color shelf life of fresh and aged beef (n = 7) Fresh Storage life (d) Storage life (d) Aged Storage life (d) storage life (d) Muscle Treament Mean CI (Liu and others 1996a) Mean CI (Liu and others 1996a) GM P to 6.2 GM G to to 3 GM G to to 3 LL P to to 10.9 LL G to to LL G2500 not discernible 8 to to SM P to to 4.1 SM G to to 3.3 SM G to to 3.4. ing a loss of color stability. However, no difference in color storage life was detected for the GM between both diets, while pasture feeding improved the color storage life of the SM by 2 d. After 10- d storage, the redness levels in the GM and SM from pasture-fed cattle were better, resulting in higher a* asymptotic values (C f ), than those from the G0 and G2500 treatments (Table 2). This enhancement of C f compensated for the detrimental effect of diet on the rate constants, increasing the color storage life. The influence of the diets on the color stability of the LL followed a different pattern. During the whole storage period the a* values of the pasture-fed LL were lower than those from the G0 and G2500 treatments, thus the C f levels of the P0 LL were also lower. This factor combined with an increase of the rate constant resulted in a significant reduction on color stability. The color storage life of the LL from pasture-fed animals was 12 d shorter than that from the unsupplemented grain-fed counterparts. The advantage of grain feeding with vitamin E supplementation as compared with pasture finishing was an increment of 1 and 2 d in color storage life for the SM and GM respectively. In the case of the LL, the improvement due to dietary vitamin E was high enough so that the limit for the color storage life was not discernible. Renerre (1984) and Liu and others (1996a) found that the color storage life of the G0 LL was longer than in the G0 SM. However, the results from the current study showed that in the case of the pasture-fed beef, the color storage life of the SM was 3-d longer than in the LL. In comparison with the G0 treatment, pasture feeding improved the color storage life in the 30-d aged SM and LL by 1 and 5 d, respectively. Results from the P0 and G2500 treatments showed that for the aged LL and SM there was no real benefit in vitamin E supplementation of grain-fed cattle over pasture feeding. Liu and others (1996a) determined the color stability at 14-d postmortem of the GM, LL, and SM of corn-fed cattle containing similar -tocopherol concentrations to those in the current study. From their results, we determined the time necessary to reach a*= 18 (Table 3). The color storage lives of fresh beef obtained in the present study were 25 to 300% higher than those reported by Liu and others (1996a). However, no difference was detected in aged LL. Although in the present study, beef was only 2-d postmortem, while Liu and others (1996a) worked with meat that had been aged for 14 d, this difference will not affect the color stability of the samples. Hood (1980) reported that the degree of discoloration was higher in meat after 2-d postmortem than in samples aged between 11 and 21 d. He also showed that aging up to 21 d Table 4 Concentration of total myoglobin (±SE) for pasture- and grain-fed beef muscle Total myoglobin (mg/g muscle) Pasture Grain LL 5.00 (± 0.92) 5.45 (± 0.49) GM 5.56 (± 0.88) 5.79 (± 0.56) SM 5.31 (± 0.94) 5.63 (± 0.86) did not affect the color stability of the LL (Hood 1980). A possible cause for the variation in color stability between the current study and that from Liu and others (1996a) may be the differences in the diets. The cattle used in the present study had access to good quality pasture immediately before the trial and were finished with a sorghum-based diet, while Liu and others (1996a) used a corn-based diet. Pasture provides high amounts of the natural form of vitamin E, the D -tocopherol that occurs as a single stereoisomer (Packer 1996), while the supplemented cattle received synthetic vitamin E or DL a-tocopheryl acetate, a mixture of 8 stereoisomers. Burton and others (1998), working with healthy human subjects, showed that the bioavailability of synthetic DL -tocopherol was roughly half that of natural D -tocopherol. Chung and others (1992) reported that D -tocopherol may be more effectively absorbed and retained by weanling swine than DL -tocopheryl acetate. Studies in rats compared the relative uptake of deuterated natural and synthetic -tocopherol. After 154 d, the ratio of natural to synthetic -tocopherol was 2.6 in lung, 1.2 in liver, and 5.3 in brain (Ingold and others 1987). In a study of 79 healthy subjects, oxidation of low-density lipoprotein was significantly delayed by daily supplementation of 400 IU of natural vitamin E; however, a similar amount of synthetic vitamin E offered a significantly lower protection (Devaraj and others 1997). Green pasture also contains carotenes (Yang and others 1992) and other antioxidants such as polyphenols. Corn and sorghum are rich in polyphenols like proanthocyanidins and phytic acid with a strong antioxidant activity. Frankel (1999) reported that the proanthocyanidins may not only act as radical scavengers but they can also have a synergistic effect by recycling vitamin E. Jood and others (1995) reported polyphenol and phytic acid concentrations in sorghum 30% higher than in corn. The cattle from the current study had access to good quality pasture immediately before the trial and were finished with a sorghum-based diet while Liu and others (1996a) used a corn-based diet. Conse- Vol. 67, Nr. 5, 2002 JOURNAL OF FOOD SCIENCE 2471

6 quently, the meat from our study may have contained a higher content of natural vitamin E, -carotenes, and polyphenols than the beef used by Liu and others (1996a) and these differences may explain the extension in storage life found in this work. Total pigment concentration Table 4 presents the total myoglobin concentration for each muscle type and nutritional background. The effect of vitamin E supplementation on the total content of myoglobin was not significant (P > 0.13); therefore, within each muscle type the data were pooled. Changing the finishing diet from pasture to grain did not alter (P > 0.30) the total myoglobin content in each muscle; therefore, the darker appearance of the pasture-fed beef was not due to a higher pigment content. Our results are in contrast to those of previous publications (Therkildsen and others 1998; Vestergaard and others 2000). However, in both studies the effect of the finishing system and animal age effects were confounded. As myoglobin concentration increased with animal age (Renerre 1990), this factor may explain the existing discrepancy. Color stability of minced beef from pasture- and grain-fed cattle Figure 3 shows the redness of minced beef (prepared from fresh and 37-d aged LL) during storage at 4 C. In accordance with previous publications (Mitsumoto and others 1993; Houben and others 1998), dietary vitamin E delayed discoloration in ground meat prepared from fresh LL. The production system had a significant effect on the redness of fresh ground LL; pasture finishing produced a darker (P < 0.05) ground meat than grain feeding. From day 1 to 6, the color stability of ground aged LL ranked as: P0 > G0 = G2500 (P < 0.01). A comparison between fresh and aged meat showed that during 6 d of storage the P0 aged samples had the best color (P < 0.05) followed by the fresh supplemented grain-fed LL. The benefits of pasture feeding on aged meat were reflected in the time necessary to reach a* = 18. Minced samples from pasture-fed aged LL remained acceptable for 6 to 7 d, whereas the control and supplemented fresh grainfed LL had a color storage life of 5 d. Pasture finishing and aging improved the color stability of ground LL by 2 d. The redness levels in the P0 fresh minced LL and in the aged G0 and G2500 mince were satisfactory for 1 to 2 d. Figure 3 Effect of pasture and grain feeding with vitamin E supplementation on the a* value of ground LL Conclusions THE ANTIOXIDANT CONCENTRATION OF PASTURE DEPENDS ON SEAsonal and climatic factors as well as on the forage species; therefore, the results from the present study may only be applicable within the experimental conditions used. The effects of nutritional background (pasture against grain) on the color and color stability of beef depended on the type of muscle. In the case of fresh beef (2-d postmortem), pasture finishing improved the color stability of color-unstable muscles like the GM or SM when compared with grain feeding with no vitamin E supplementation. However, the LL from pasture-fed cattle was darker than that from grain-fed steers. Although in this experiment pasture and supplemented grain fed cattle had similar -tocopherol concentrations in muscle, the color and color stability of supplemented grain-fed beef was better. After 30-d aging, meat from pasture-fed cattle had similar color and color stability to supplemented grain-fed beef and better than that from nonsupplemented grain-fed beef. As aging is a recommended practice, pasture finishing presents some advantages over grain feeding in terms of color stability. References Bidner TD, Schupp AR, Montgomery RE, Carpenter JC Acceptability of beef finished on all forage, forage plus grain or high-energy diets. 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7 Mitsumoto M, Arnold RN, Schaefer DM, Cassens RG Dietary versus postmortem supplementation of vitamin E on pigment and lipid stability in ground beef. J Anim Sci. 71(7): Packer L Antioxidant defenses in biological systems. In: Packer L, Traber MG, Wenjuan X, editors, Proc. Int. CSymposium on Natural Antioxidants, molecular mechanisms and health effects. Champaign ILL: AOCS Press, P Reagan JO, Carpenter JA, Bauer FT, Lowry RS Packaging and palatability characteristics of grass and grass-grain fed beef. J Anim Sci 45(4): Renerre M Variability between muscles and between animals of the color stability of beef meats. Sci Alim 4(4) Renerre M Factors involved in the discoloration of beef meat. Int J Food Sci Technol 25: Renerre M, Bonhomme J Effect of electrical stimulation, boning temperature and conditioning mode on display colour of beef meat. Meat Sci 29(3): SAS Institute Inc SAS User s guide statistics. SAS Institute Inc., Cary, NC, USA. Schaefer DM, Liu QP, Lanari MC Dietary vitamin E delays beef myoglobin and lipid oxidations. In: Coelho M, editor. Vitamin E in animal nutrition and management. BASF Corp. Mount Olive, NJ. p Srinivasan S, Xiong YL, Blanchard SP, Moody WG Proximate mineral and fatty acid composition of semimembranosus and cardiac muscles from grass and grain-fed and zeranol-implanted cattle. Food Chem 63: Therkildsen M, Vestergaard M, Jensen LR Andersen HR, Sjersen K Effect of feeding level, grazing and finishing on growth and carcass quality of young Friesian bulls. Acta Agric Scand, Sect A, Animal Sci 48: Thomas JD Quantitative and qualitative characteristics of forage and grainfed beef and ultrastructure of beef muscle as affected by sample preparation and cookery method. Diss Abst Int B42(3). van Laack RLJM, Berry BW, Solomon MB Variations in internal color of cooked beef patties. J Food Sci 61(2): Vatansever L, Kurt E, Scollan ND, Richardson I, Nute GR, Wood J The quality of beef from steers fed supplements of -2 polyunsaturated fatty acids. Proc 44 th Int. Congress Meat Sci & Technol. p Vestergaard M, Oksbjerg N, Henckel P Influence of feeding intensity, grazing and finishing feeding on muscle fiber characteristics and meat color of semitendinosus, longissimus dorsi and supraspinatus muscles of young bulls. Meat Sci 54(2): Yang A, Larsen TW, Tume RK Carotenoid and retinol concentrations in serum, adipose tissue and liver and carotenoid transport in sheep, goats and cattle. Australian Journal of Agricultural Research, 43: MS Submitted 3/21/01, Revised 5/20/01, Accepted 5/21/01, Received 5/31/01 We thank Meat and Livestock Australia for their support of this project. We thank Dr Heather Bruce, Mr Andrew Pow, Ms Sharon Rablin, Dr Robin Shorthose and Ms Larisa Skyring for their helpful assistance and Dr David Taylor and staff, Univ. of Queensland Gatton College, for managing the feeding trial. We would also like to acknowledge Dr Bob Elliott of Roche Products Pty Ltd, Vitamins and Fine Chemicals Division, Goodna, Qld for providing the vitamin E preparations. Authors are with Food Science Australia, Brisbane Laboratory, P.O. Box 3312 Tingalpa DC Qld 4173, Australia. Direct inquiries to author Lanari ( Maria.Lanari@foodscience.afisc.csiro.au). Vol. 67, Nr. 5, 2002 JOURNAL OF FOOD SCIENCE 2473