Elsevier

Meat Science

Volume 70, Issue 1, May 2005, Pages 35-44
Meat Science

Influence of pasture or grain-based diets supplemented with vitamin E on antioxidant/oxidative balance of Argentine beef

https://doi.org/10.1016/j.meatsci.2004.11.018Get rights and content

Abstract

Argentine meat has been traditionally produced on pasture. However, to comply with some market requirements, grain finishing is becoming more common among producers. The main goal of the present work was to study lipid oxidation in fresh meat from animals fed different diets in relationship with their antioxidant vitamin status. Attributes were evaluated in beef from pasture or grain-fed animals with (PE and GE) or without supplementation (P and G) with vitamin E (500 UI/head/day). Fresh meat produced on grain (G and GE) had higher fat (4.0 ± 1.6 and 4.7 ± 1.4 g/100 g) and cholesterol content (51.0 ± 3.0 and 52.0 ± 4.0 mg/100 g) than meat from pasture (P and PE) fed animals (2.7 ± 1.2 to 2.9 ± 1.1 g/100 g and 48.0 ± 5.0 to 49.0 ± 4.0 mg/100 g of intramuscular fat and cholesterol respectively). Fatty acid composition was clearly affected by diet. Beef from pasture-fed cattle had higher percentage of linolenic acid, less linoleic acid and, overall, higher percentage of polyunsaturated fatty acids than beef from grain-fed animals (P < 0.05).

Thiobarbituric acid reactive substances number and volatile levels of hexanal, pentanal, heptanal, octanal and 3-methylbutanal were higher in grain than in pasture samples (P < 0.05). P + PE meat had higher content of antioxidant vitamins than G + GE samples (P < 0.001). Values ranged from: 15.92 ± 3.48 (G) to 17.39 ± 4.29 (GE) and 25.3 ± 10.0 (P) to 21.98 ± 5.11 (PE) μg/g of ascorbic acid; from 1.05 ± 0.73 (G) to 1.76 ± 0.97 (GE) and 3.08 ± 0.45 to 3.91 ± 0.74 μg/g of α-tocopherol; and from 0.06 ± 0.03 (G) to 0.05 ± 0.01 (GE) and 0.45 ± 0.21 (P) to 0.63 ± 0.27 (PE) μg/g of β-carotene. In addition, principal component analysis clearly separated grain from pasture samples regardless of their supplementation with vitamin E. This level of supplementation did not improve the antioxidant status of fresh meat (P > 0.05). We conclude that pasture diet contributes natural antioxidants in sufficient amounts and is an efficient way to prevent lipid oxidation in fresh beef.

Introduction

Oxidative damage is the major non-microbial factor responsible for quality deterioration of muscle foods. Particularly, the oxidative status of meat is indicated by its colour stability and susceptibility to rancidity.

Lipid oxidation in muscle foods is initiated by stressors arising from both internal and external sources. The most important stressors are the reactive oxygen species (ROS) including free radicals and peroxides (Morrisey, Sheehy, Galvin, Kerry, & Buckeley, 1998).

During handling, processing and storage of fresh meat, released endogenous iron is partially responsible for the catalysis of lipid oxidation (Gutteridge et al., 1981, Halliwell and Gutteridge, 1986).

Propagation of lipid peroxidation in membranes promotes myoglobin oxidation resulting in colour deterioration, formation of rancid odours and other off-flavours in fresh meat (Gorelik & Kanner, 2001). Red meat is specially susceptible to the prooxidant effect of haem proteins in combination with endogenous iron (Monahan, Crackel, Gray, Buckeley, & Morrissey, 1993).

The action of ROS is opposed by enzymatic and non-enzymatic antioxidant defence systems (Halliwell, 1997). Among the non-enzymatic antioxidants, vitamin E, and more specifically α-tocopherol, is widely recognised as enhancer of the antioxidant activity in meat. Many authors described its usefulness in diminishing discoloration of meat induced by oxidation (Arnold et al., 1993, Faustman et al., 1998). Moreover, several authors reported a negative correlation between oxidation and α-tocopherol levels in fresh bovine meat (Gatellier et al., 2001, Jakobsen and Bertelsen, 2000, Lawlor et al., 2000, Renerre et al., 1999).

Supranutritional supplementation with vitamin E to finishing steers improved beef colour as well as suppressed lipid oxidation and stabilised cell integrity. Therefore, supplementation of animal diets with vitamin E has been strongly proposed as a production strategy (Arnold et al., 1993, Faustman et al., 1989, Faustman et al., 1998, Liu et al., 1995, Mitsumoto et al., 1993, Mitsumoto et al., 1995).

Nevertheless, in addition to α-tocopherol content, some other factors that influence oxidative stability in muscle should be considered. For example, the contribution of polyunsaturated fatty acids content (PUFA > 18:2), upon the balance between pro-oxidant/antioxidant compounds (Jensen, Lauridsen, & Bertelsen, 1998).

β-carotene is another important fat soluble antioxidant that quenches sites localised within the hydrophobic region of biological membranes, contrasting with the scavenging activity of α-tocopherol close to the membrane surface (Fukuzawa, Inokami, Tokumura, Terao, & Suzuki, 1998). Therefore, although β-carotene is less reactive than α-tocopherol, both antioxidants can exert a co-operative antioxidant activity at different positions within the membrane (Tsuchihashi, Kigoshi, Iwatsuki, & Niki, 1995).

Pasture consumed by cattle is known to supply vitamin E requirements in addition to other natural antioxidants (Gatellier, Mercier, & Renerre, 2004). On the other hand, studies have shown that pasture feeding led to increased values of highly unsaturated fatty acids (Garcı́a et al., 1999, Larick and Turner, 1989, Melton et al., 1982, Yang et al., 2002b). Argentine beef has been traditionally produced on pasture. However, in order to comply with some market requirements, regarding consumer’s preference for meat with more marbling, grain supplementation is becoming more common among producers.

During post-slaughter, cellular antioxidant defences may no longer be tightly activated. Therefore, a considerable antioxidant status must be achieved before slaughter in order to maximise the protection of muscle lipids against peroxidation. The aim of this work was to determine naturally occurring antioxidant activity in fresh Argentine beef achieved by different production systems, and their relationship with lipid oxidation parameters.

Section snippets

Animals and diets

This study was part of a project conducted to determine the influence of finishing diets on meat quality and oxidative stability of fresh and aged meat of crossbreed steers.

Pasture: Twenty crossbreed steers were grown on green natural pastures composed mainly by tall fescue (Festuca arundinacea Schreb.), rescue grass (Bromus catharticus), alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) under continuous grazing at a forage rate of 1000/2000 kg dried pasture/ha. Ten

α-Tocopherol and β-Carotene contents in plasma and muscle homogenates

Vitamin E supplementation did not affect carcass quality or yield characteristics. As expected, the grain production system resulted in a major daily weight gain, but carcasses yielded the same at slaughter time with 480 kg live weight (Table 1).

Vitamin E supplementation increased fourfold the α-tocopherol content in plasma of grain-fed animals, which reached levels equivalent to those found for the pasture-fed group. However, no increment was detected in supplemented pasture-fed group when

Conclusions

Pasture diet improved the oxidative stability in PM muscle. As well, it contributed to reduce the n  6/n  3 fatty acids ratio in intramuscular fat and consequently may improve the nutritional quality of beef.

Principal component analysis differentiated meat from pasture or grain-fed animals when oxidation and antioxidant parameters were considered together. This effect was not influenced by supplementation of diets with 500 UI vitamin E/head/day. In addition, this work supports research indicating

Acknowledgements

The authors gratefully acknowledge the enthusiastic interest and skilled assistance of Ms. Ilda Avila and Ms. Rina Reynoso. We also thank Roche Argentina for providing the vitamin E preparations.

This study was financed by the National Agency of Science and Technology (ANPCyT) PICT 09-03517, BID 1201/OC-AR.

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