- Email: [email protected]
Effect of Dietary Vitamin E on the Oxidative Stability of Raw and Cooked Rabbit Meat
Meat Science, Vol. 50, No. 2, 153±161, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain PII: S0309-1740(98)00026-6 0309-1740/98/$19.00+0.00
Eect of Dietary Vitamin E on the Oxidative Stability of Raw and Cooked Rabbit Meat C. Castellini,a* A. Dal Bosco,a M. Bernardinia & H. W. Cyrilb a
Istituto di Zootecnica Generale, FacoltaÁ di Agraria, UniversitaÁ di Perugia, Borgo XX Giugno 74, 06100 Perugia, Italy b Department of Animal Science, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka (Received 24 October 1997; revised version received 9 March 1998; accepted 12 March 1998)
ABSTRACT The eect of dietary a-tocopheryl acetate supplementation (200 mg/kg diet) on plasma and muscle levels of a-tocopherol and the oxidative stability of raw and cooked rabbit meat was determined. Two groups of 20 male hybrid rabbits were fed the experimental diets from 35 to 80 days of age. Feed intake, live weight, feed eciency and qualitative traits of the carcass and meat were recorded. The a-tocopherol levels in plasma and muscle were signi®cantly higher (p0.01) in the supplemented group, which also showed an increase in oxidative stability in both raw and cooked meat. The higher a-tocopherol level improved the physical traits of the meat, signi®cantly reducing shear value and increasing water-holding capacity; n-3 fatty acids in raw and cooked meat increased (p0.05) and the thrombogenic index decreased (p0.05). Dietary vitamin E did not in¯uence weight gain, feed intake and dressing yield. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION Rabbit meat is widely consumed in almost all of Europe (Italy, France, Spain, Portugal, Belgium and Hungary) as well as in other countries like the Ukraine, China and Russia where over 100 000 tonnes are consumed (Colin and Lebas, 1996). Rabbit meat has many positive dietetic characteristics for example low lipid and cholesterol levels and a high content of polyunsaturated fatty acids (PUFA), which can be further increased by speci®c dietary strategies (Castellini and Dal Bosco, 1998). Reported bene®ts of long-chain PUFA, mainly C20:5n3 and C22:6n3, on human health (Kinsella et al., 1990; Nettleton, 1991) have increased the interest in animal products with high levels of these acids (Hargis and Van Elswik, 1993; Nash et al., 1995). Unfortunately PUFA easily undergoes peroxidative damage during storage and cooking and as a consequence ¯avour, colour, texture and *To whom correspondence should be addressed. Fax: 00 39 75 585 3122; e-mail: [email protected] 153
154
C. Castellini et al.
nutritional value are decreased (Kanner et al., 1991) and atherogenic compounds can be generated (Addis and Park, 1989). The incorporation of antioxidants in the diet has shown favourable eects on meat characteristics of dierent species. Intake of vitamin E above the daily requirement increased a-tocopherol levels in plasma and tissues, improving lipid stability (Lin et al., 1989; Liu et al., 1995). In the rabbit protection against peroxide damage depends on vitamin E rather than on selenium (Cheeke, 1987) because the kidneys and liver have a high level of non-seleniumdependent glutatione peroxidase activity (Lee et al., 1979), hence the vitamin E requirement for rabbits is higher than for ruminants (Jenkins et al., 1970). Our previous ®ndings (Bernardini et al., 1996) demonstrated the positive role of vitamin E in protecting raw meat from peroxidation mainly in rabbits fed diets containing a small amount of ®sh meal. The aim of the present study was to con®rm these results and to check the eectiveness of supplemental dietary vitamin E in preventing the peroxidative processes in cooked meat. MATERIALS AND METHODS Animals and diets The study was carried out at the experimental rabbitry of the Animal Production Institute of the University of Perugia where the temperature was 18.53.1 C and the photoperiod was 16 h light/day. Forty hybrid males, weaned at 35 days, were divided into two homogeneous groups and fed ad libitum standard diets with 2% herring meal to enrich the long-chain n-3 fatty acids (>20 carbons) (Bernardini et al., 1996). The diet of group 1 was supplemented with a low level of a-tocopheryl acetate, (50 mg/kg diet, control) and that of group 2 with a high level of a-tocopheryl acetate (200 mg/kg supplemented). The ingredients and chemical composition of the diets are presented in Tables 1 and 2, respectively. TABLE 1 Ingredients of Rabbit Diet Ingredient Dehydrated alfalfa meal Barley meal Soyabean meal Fish meal Wheat straw Molasses CaCo3 Calcium diphosphate Ligninsulfunate Salt Coccidiostatic DL-methionine Vitamin±mineral premixa -tocopheryl acetate
% composition 40 31.5 18 2 4 0.8 1 0.6 0.5 0.5 versus 0.4985 0.06 0.04 1 0 versus 0.0015
Added per kg: vit. A 11 000 UI; vit. D3 2000 UI; vit. B1 2.5 mg; vit. B2 4 mg; vit. B6 1.25 mg; vit. B12 0.01 mg; -tocopheryl acetate 50 mg; biotine 0.06 mg; vit. K 2.5 mg; niacine 15 mg; folic acid 0.30 mg; d-panthotenic acid 10 mg; choline 600 mg; Mn 60 mg; Fe 50 mg; Zn 15 mg; 10.5 mg; Co 0.5 mg. a
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
155
TABLE 2 Chemical Composition and Nutrititional Value of the Diets Crude protein Ether extract Crude ®bre Ash N-free extract NDF-Neutral Detergent Fiber ADF-Acid Detergent Fiber ADL-Acid Detergent Liquid Hemicellulose Cellulose Digestible energy (estimated) -tocopherol
% dry matter " " " " " " " " " MJ/kg dry matter mg/kg
17.75 2.74 17.58 8.65 53.28 29.19 19.35 3.57 9.84 15.48 10.26 67 versus 263
Feed intake and live weight were recorded weekly and feed eciency was estimated as the ratio between consumption and weight gain. In vivo antioxidant capacity At 84 days of age, blood samples were drawn. The blood was collected over Na2ETDA (1±2 mg/ml blood) and immediately centrifuged (10 000 g for 10 min at 4 C). The supernatant was used for evaluating plasma antioxidant capacity expressed as total (Peroxil) radical-trapping antioxidant parameter (TRAP) (Miller et al., 1993). Slaughter, sample collection and physical analyses Rabbits were sacri®ced at 84 days of age. The drip loss was calculated as the dierence between the weight of hot and refrigerated carcasses (at 4 C for 24 hr), according to Blasco et al. (1993). From the refrigerated carcasses longissimus dorsi muscles were removed and carefully freed from connective and adipose tissues and a portion of them was used for chemical and physical analyses, (cooking loss, water-holding capacity, shear force and colour). Samples (622 cm) of about approximate 20 g were placed in open aluminium boxes and cooked for 15 min in an electric oven pre-heated to 200 C (Cyril et al., 1996). After cooking, the samples were dried with a paper towel. Total cooking loss was estimated on each sample cooled for 30 min to 15 C as the percentage ratio between cooked and raw weight. Water-holding capacity (WHC) was estimated, as indicated by Nakamura and Katoh (1985), by centrifuging 1 g of muscle for 4 min at 1500 g and determining the residual water by drying the sample at 70 C overnight. WHC was calculated as follows: WHC
weight after centrifugation ÿ weight after drying 100 initial weight
Shear force was evaluated on cores (1.25 2 cm) obtained from the mid-portions of the cooked samples by cutting them perpendicular to ®ber direction, using an Instron, model 1011, equipped with Warner-Blatzler meat shear apparatus. The colour parameters (L*, a*, b*) were evaluated using a tristimulus analyser (Minolta Chroma Meter CR-200) with the CIELAB Colour System (1976); from the chromaticity coordinates, hue and chroma were calculated.
156
C. Castellini et al.
Chemical analyses The chemical composition of the diets was analysed according to AOAC (1995), methods (1995). The -tocopherol level in diets, plasma and meat was determined by high performance liquid chromatography (Zaspel and Csallany, 1983). The fatty acids in the diets and meat were extracted according to Folch et al. (1957) and determined as methyl esters with a gas chromatograph using a DB wax capillary column (25 mm 1, 30 m length). Atherogenic and thrombogenic indices were calculated as indicated by Ulbricht and Southgate (1991). Lipid oxidation was assessed by the 2-thiobarbituric acid (TBARS) method (Ke et al., 1977) and expressed as mol malonaldehyde/kg tissue. Statistical analyses Statistical analyses were done using the following linear models [SAS/STAT (1990) GLM]: . Chemical composition of diets and in vivo parametersЮxed eect of diet (control versus supplemented); . Post-mortem itemsÐinteractive eect of diet and processing (raw versus cook meat). Statistical signi®cance of dierences were assessed by the t-test (SAS/GLM option PDIFF). RESULTS AND DISCUSSION -tocopherol level of diets The -tocopherol levels of the diets were 67 and 263 mg/kg diet (Table 2), indicating a good resistance of -tocopheryl acetate to feed processing (mixing and pelletting). Growing performance and plasma antioxidant capacity Productive performance was not signi®cantly aected by diet (Table 3). Only a slight reduction of feed intake (about 4 g/day) and a resulting lower weight gain (about 3 g/day) TABLE 3 Eect of -tocopheryl Acetate Supplementation on Productive Performance and Plasma Parameters Parameter
Slaughter weight Commercial carcass weight Dressing yield Weight gain Feed intake Feed eciency -tocopherol level Antioxidant capacity (TRAP) n=40; A,B = p0.01.
Treatment
g g % g/day g/day g/ml mol/l
Control
Supplemented
SE
2822.85 1752.85 62.14 38.29 140.16 3.69 1.56A 305.2A
2670.50 1676.28 62.73 35.12 136.24 3.92 4.67B 415.2B
305.66 199.40 1.55 5.54 7.06 0.59 1.65 51.0
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
157
were observed in supplemented animals; this is in agreement with previous ®ndings in beef (Arnold et al., 1993a). Autocatalytic peroxidation in muscle begins immediately after slaughter. The balance between pro-oxidative factors and antioxidant capacity aects the oxidative stability of tissues and consequently of meat (Buckley et al., 1995). In blood plasma there is a complex antioxidant system and although -tocopherol provides only a marginal contribution to TRAP (about 5±10%) it plays a speci®c role in trapping radicals directly and avoiding breakage of the fatty acid chain (Wayner et al., 1987). In our trial (Table 3) the plasma -tocopherol level increased signi®cantly (1.56 versus 4.67 g/ml; p0.01) according to the dietary level, which is in agreement with reports by other authors in other species (Bartov and Frigg, 1992; Arnold et al., 1993a). The plasma antioxidant capacity showed the same trend (305.2 versus 415.2 (mol/l; p0.01), con®rming our previous results (Bernardini et al., 1996). Physical characteristics, -tocopherol level and oxidative stability of raw and cooked meat Vitamin E supplementation signi®cantly (p0.05) reduced drip loss in the carcass (1.06 versus 1.56%) and shear force (4.53 versus 5.17 kg/cm2) in the cooked meat (Table 4). The positive eect on drip loss, although calculated dierently, has also been reported by Monahan et al. (1990) in pig and Mitsumoto et al. (1995) in beef. Asghar et al. (1989) suggested that -tocopherol preserves biomembranes and their ability to act as a semipermeable barrier, reducing the exudative loss (Stanley, 1991). In addition, Cheah et al. (1995) observed a positive eect of dietary vitamin E supplementation on drip loss and membrane stability. This eect is presumably due to the inhibition of phospholipase A2 activity, which consequently reduces the freeing of long-chain phospholipids from mitochondria and Ca++ release with a consequent decrease of post-mortem glycolysis and drip loss. As regards the weight loss a slightly higher value in the treated group was obtained, which is in agreement with Mitsumoto et al. (1995), who observed, in beef, that TABLE 4 Eect of -tocopheryl Acetate on Physical Traits of Raw and Cooked Meat, on of -tocopherol level and TBARS Parameter
Moisture Drip loss of carcass Shear value WHC Cooking loss
Raw
%. % kg/cm2 % %
Colour L* a* b* hue chroma -tocopherol level TBARS
/g mol/ MDA/kg
n=80; A,B: p0.01; a,b: p0.05.
Cooked
SE
Control
Supplement
Control
Supplement
75.58A 1.56b 3.21a 57.11b Ð
76.94B 1.06a 2.95a 58.98c Ð
52.36 Ð 5.17c 48.98a 30.72
52.13 Ð 4.53b 50.02a 32.25
1.05 0.32 1.09 1.15 1.48
58.65A 5.53B 0.85A 0.25A 5.62A 1.14A 1.34b
60.72A 5.17B 1.09A 0.18A 5.63A 3.51B 0.71a
80.13B 3.97A 10.67B 1.21B 11.40B 1.08A 9.33B
81.32B 3.78A 9.52B 1.17B 10.30B 3.11B 3.45A
2.30 0.56 2.38 0.08 2.27 0.15 1.19
158
C. Castellini et al.
dietary vitamin E supplementation shifted weight loss from drip loss to cooking loss. As previously stated, supplementation presumably aected the integrity of the muscle ®ber, and consequently the moisture (p0.01) and WHC (p0.05) of the fresh muscle increased. Colour parameters did not show variations ascribable to the diet. Faustman et al. (1989) reported that the eect of vitamin E on the level of metmyoglobin, which causes the brown pigmentation of meat, was evident after some days of storage, while after 24 h only a light decrease of a* (red index) appeared in treated animals. It is also possible that in rabbit meat the oxidative processes are slower and less manifest because of the low amount of myoglobin. The -tocopherol level in raw muscle (Table 4) was signi®cantly higher (3.51 versus 1.14 g/g; p0.01) on increasing the dietary level to 200 mg/kg, in agreement with reports in rabbit (Lopez-Bote et al., 1997), poultry (Sklan et al., 1983), pig (Monahan et al., 1990) and beef (Arnold et al., 1993b; Liu et al., 1994). The level of -tocopherol was not reduced by cooking, as also reported by Liu et al. (1994), con®rming that vitamin E withstands heating (Machlin, 1984) and thus performs as an antioxidant also in cooked products (Faustman et al., 1989). This fact has positive implications in human nutrition because vitamin E, besides the speci®c protection of n-3 fatty acids, reduces cholesterol oxidation and therefore its cytotoxicity and atherogenecity (Kumar and Singhal, 1991). The oxidative processes in muscle are negatively correlated with -tocopherol level; the lowering of TBARS is equal to 47% in fresh meat and 63% in cooked meat. TBARS values in fresh muscle agree with those obtained in rabbit by Lopez-Bote et al. (1997) and in other animal species by Tsai et al. (1978) and Wulf et al. (1995). For cooked meat, our TBARS values are higher than those reported in beef and pig (Monahan et al., 1990; Liu et al., 1994). Furthermore, the positive eect of supplementation was more evident in our trial. According to Allen and Foegeding (1981), one of the most important factors aecting lipid oxidation in muscle is the PUFA content. The high PUFA level of rabbit meat probably activates more intense peroxidative processes; in these conditions the eectiveness of vitamin E could be greater. Fatty acid composition of meat Supplementary -tocopheryl acetate signi®cantly increased the n-3 fatty acid level (Table 5), both in raw (+14.1%) and in cooked meat (+37.6%). Tsai et al. (1978) did not observe, in swine, variations either in the fatty acid distribution or in the amount of unsaturation, but the authors did not analyse the long-chain PUFA, which in our trial contributed to making the dierences consistent. Lopez-Bote et al. (1997) did not observe any signi®cant eect of vitamin E supplementation on the fatty acid pro®le of rabbit in polar and neutral lipids. This disagreement is probably due to the presence of herring meal in our diets, which enhanced the protective eect of -tocopherol. The atherogenic index did not show signi®cant variations, while the trombogenic index was lower in supplemented animals with the higher n-3 level. It is concluded that -tocopheryl acetate supplementation was eective in increasing vitamin E and n-3 PUFA in raw and cooked meat, and in reducing the thrombogenic index, with consequent bene®ts on the nutritional quality for consumers. In fact, an increased intake of n3 fatty acids without adequate antioxidant protection could result in increased free radicals and lipid oxidative by-products (Wander et al., 1997). In this context, the supplementation of 200 mg/kg vitamin E provides a very dietetic meat, rich in n-3 and adequately protected. Further research is needed to ascertain the vitamin E dose with respect to duration of administration, and the eventual synergy between vitamin E and vitamin C in protecting the meat from oxidative processes during cooking and storage.
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
159
TABLE 5 Eect of -tocopheryl Acetate on Fatty Acid Composition (g per 100 g) in Raw and Cooked Meat Fatty acid
C8:0 C10:0 C12:0 C14:0 C14:1n6 C15:0 C16:0 C16:1n7 C17:0 C18:0 C18:1n9 C18:2n6 C18:3n6 C18:3n3 C18:4n3 C20:1n6 C20:2n6 C20:3n6 C20:4n6 C20:3n3 C20:5n3 C21:5n3 C22:5n3 C22:6n3 C24:0 C24:1 SFA MUFA PUFA n-3 Atherog. index Tromb. index
Raw
Cooked
Control
Supplement
Control
Supplement
0.55 0.42 0.44 3.25 0.45 0.76 27.77a 3.61 0.65 5.81 20.75 25.33b 0.17 2.64 0.96A 0.10 0.12a 0.36 3.83 0.04 0.18A 0.05A 0.48 0.75a 0.15a 0.38 39.80 25.30 34.90b 5.10b 0.68 0.86b
0.45 0.44 0.60 3.62 0.49 0.81 28.49a 4.11 0.73 4.47 19.74 24.61b 0.17 2.55 1.42A 0.12 0.11a 0.41 3.85 0.06 0.29B 0.15B 0.49 0.96b 0.28b 0.58 39.91 25.04 35.05b 5.92c 0.70 0.80a
0.65 0.60 0.61 3.56 0.45 0.87 30.56b 3.40 0.74 5.31 20.15 23.27ab 0.11 2.72 0.83A 0.10 0.20b 0.35 3.81 0.05 0.12A 0.17B 0.11 0.63a 0.15a 0.48 43.05 24.58 32.37a 4.63a 0.79 0.97c
0.41 0.47 0.49 3.63 0.46 0.83 30.35b 3.85 0.66 5.31 20.20 22.41a 0.02 2.45 1.27B 0.13 0.22b 0.57 3.48 0.03 0.26B 0.23B 0.34 0.79a 0.27b 0.47 42.42 25.11 32.43a 5.37b 0.78 0.87b
SE 0.43 0.35 0.24 0.73 0.15 0.10 2.65 1.24 0.07 2.11 2.45 2.59 0.09 0.46 0.68 0.09 0.06 0.58 0.95 0.05 0.07 0.06 0.24 0.26 0.06 0.15 3.41 3.01 2.99 0.67 0.11 0.10
n=80; A,B = p0.01; a,b,c = p0.05.
ACKNOWLEDGEMENT Research supported by the National Research Council of Italy. Special Project RAISA. Sub-Project no. 3. Paper no. 2984. REFERENCES Addis, P. B. and Park, S. W. (1989) Role of lipid oxidation products in atherosclerosis. In: Food Toxicology, a perspective on the relative risk, eds. S. Raylor and R. Scanalan, pp. 297±330. Marcel Dekker, New York. Allen, C. E. and Foegeding, E. A. (1981) Some lipid characteristics and interactions in muscle foods. A review. Food Technology 35, 253±257.
160
C. Castellini et al.
AOAC (1995). Ocial Methods of Analysis. 15th Edn. Association of Ocial Analytical Chemists, Washington. Arnold, R. N., Scheller, K. K., Arp, S. C., Williams, S. N. and Shaefer, D. M. (1993a) Dietary atocopheryl acetate enhances beef quality in Holstein and beef breed steers. Journal of Food Science 58, 28±33. Arnold, R. N., Arp, S. C., Scheller, K. K., Williams, S. N. and Shaefer, D. M. (1993b) Tissue equilibration and subcellular distribution of vitamin E relative to myoglobin and oxidation in displayed beef. Journal of Animal Science 71, 105±118. Asghar, A., Lin, C. F., Gray, J. I., Buckley, D. J., Booren, A. M., Crackel, R. L. and Flegal, C. J. (1989) In¯uence of oxidised oil and antioxidant supplementation on membrane bound lipid stability in broiler meat. British Poultry Science 30, 815±823. Bartov, I. and Frigg, M. (1992) Eect of high concentrations of dietary vitamin E during various age periods on performance, plasma vitamin E and meat stability of broiler chicks at 7 weeks of age. British Poultry Science 33, 393±402. Bernardini, M., Dal Bosco, A., Castellini, C. and Miggiano, G. (1996) Dietary vitamin E supplementation: antioxidant capacity and meat quality. Proceedings of the 6th World Rabbit Congress, 3, 137±140. Blasco, A., Ouhayoun, J. and Masoero, G. (1993) Harmonization of criteria terminology in rabbit meat research. World Rabbit Science 1, 3±10. Buckley, D. J., Morrissey, P. A. and Gray, J. I. (1995) In¯uence of dietary vitamin E on the oxidative stability of pig meat. Journal of Animal Science 73, 3122±3130. Castellini, C. and Dal Bosco, A. (1998) Eect of dietary herring meal on the omega-3 content of rabbit meat. Proceedings in Food and Health, Elsevier, pp. 67±71. Cheah, K. S., Cheah, A. M. and Krausgrill, D. I. (1995) Eect of dietary supplementation of vitamin E on pig meat quality. Meat Science 39, 255±263. Cheeke, P. R. (1987) Vitamins. In Rabbit Feeding and Nutrition, ed. T. J. Cunha. Vol. 9, pp. 145± 147. Gainesville, Florida. Academic Press, London. CIELAB Colour System (1976) Commission International de l'Eclairage. CIE, Publcation 36, Paris. Colin, M. and Lebas, F. (1996) Rabbit meat production in the world. A proposal for every country. Proceedings of the 6th World Rabbit Congress, 3, 323±330. Cyril, H. W., Castellini, C. and Dal Bosco, A. (1996) Comparison of three cooking methods of rabbit meat. Italian Journal of Food Science 8, 337±340. Faustman, C., Cassens, R. G., Schaefer, D. M., Buege, D. R., Williams, S. N. and Scheller, K. K. (1989) Improvement of pigment and lipid stability in Holstein steer beef by dietary supplementation with vitamin E. Journal of Food Science 54, 858±867. Folch, J., Lees, M. and Sloane-Stanley, H. (1957) A simple method for the isolation and puri®cation of total lipids from animal tissues. Journal of Biology and Chemistry 226, 497±509. Hargis, P. S. and Van Elswik, M. E. (1993) Manipulating the fatty acid composition of poultry meat and eggs for the health conscious consumer. World's Poultry Science Journal 49, 251±264. Jenkins, K. L., Hidiroglou, M., MacKay, R. R. and Proulx, J. G. (1970) In¯uence of selenium and linoleic acid on the development of nutritional muscolar dystrophy in beef calves, lambs and rabbits. Canadian Journal of Animal Science 50, 137±146. Kanner, J., Harel, S. and Granit, R. (1991) Oxidative processes in meat and meat products: quality implications. Meat Science 36, 169±189. Ke, P. J., Ackman, R. G., Linke, B. H. and Nash, D. M. (1977) Dierential lipid oxidation products in various parts of frozen mackerel. Journal of Food Technology 12, 37±47. Kinsella, J. E., Lokesh, B. and Stone, R. A. (1990) Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular disease: possible mechanism. American Journal of Clinical Nutrition 52, 1±28. Kumar, N. and Singhal, O. P. (1991) Cholesterol oxides and atherosclerosis: a review. Journal of Science of Food Agriculture 55, 497±512. Lee, Y. H., Layman, D. K. and Bell, R. R. (1979) Selenium-dependent and non selenium-dependent glutathione peroxidase activity in rabbit tissue. Nutrition Reproduction International 20, 573±578. Lin, C. F., Asghar, A., Gray, J. I., Buckley, D. J., Booren, A. M., Crackel, R. L. and Flegal, C. J. (1989) Eects of oxidised dietary oil and antioxidant supplementation on broiler growth and meat stability. British Poultry Science 30, 855±864.
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
161
Liu, Q., Scheller, K. K., Schaefer, D. M., Arp, S. C. and Williams, S. N. (1994) Dietary a-tocopheryl acetate contribute to lipid stability in cooked beef. Journal of Food Science 59, 288±290. Liu, Q., Lanari, M. C. and Schaefer, D. M. (1995) A review of dietary vitamin E supplementation for improvement of beef quality. Journal of Animal Science 73, 3131±3140. Lopez-Bote, C. J., Rey, A. I., Sanz, J. I. and Gray, J. I. (1997) Dietary vegetable oils and a-tocopherol reduce lipid oxidation in rabbit muscle. Journal of Nutrition 127, 1176±1182. Machlin, L. J. (1984) Vitamin E. In Handbook of Vitamins: Nutritional, Biochemical and Clinical Aspects, ed. L. Machlin pp. 99±145. Marcel Dekker, New York. Miller, N. J., Rice-Evans, C., Davies, M. J., Gopinathan, V. and Milner, A. (1993) A novel method for measuring antioxidant capacity and its application to monitoring the antioxidant status in premature neonates. Clinical Science 84, 407±412. Mitsumoto, M., Arnold, R. N., Schaefer, D. M. and Cassens, R. G. (1995) Dietary vitamin supplementation shifted weight loss from drip to cooking loss in fresh beef longissimus during display. Journal of Animal Science 73, 2289±2294. Monahan, F. J., Buckley, D. J., Gray, J. I. and Morrissey, P. A. (1990) Eect of dietary vitamin E on the stability of raw and cooked pork. Meat Science 27, 99±108. Nakamura, M. and Katoh, K. (1985) In¯uence of thawing method on several properties of rabbit meat. Bulletin of Ishikawa Prefecture College of Agriculture, Japan 11, 45±49. Nash, D. M., Hamilton, R. M. G. and Hulan, H. W. (1995) The eect of dietary herring meal on the omega-3 fatty acid content of plasma and egg yolk lipids of laying hens. Canadian Journal of Animal Science 2, 247±253. Nettleton, J. A. (1991) n-3 fatty acids: comparison of plant and seafood sources in human nutrition. Journal of American Dietetic Association 91, 331±337. SAS/STAT (1990) User's guide, Version 6, Cary, NC. Sklan, D., Tenne, Z. and Budowski, P. (1983) The eect of dietary fat and tocopherol on lipolysis and oxidation in turkey meat stored at dierent temperatures. Poultry Science 62, 2017±2021. Stanley, D. W. (1991) Biological membrane deterioration and associated quality losses in food tissues. Critical Review of Food Nutrition 30, 487±495. Tsai, T. C., Wellington, G. H. and Pond, W. G. (1978) Improvement in the oxidative stability of pork by dietary supplementation of swine rations. Journal of Food Science 43, 193±196. Ulbricht, T. L. V. and Southgate, D. A. T. (1991) Coronary heart disease: seven dietary factors. The Lancet 338, 985±990. Wander, R. C., Hall, J. A., Gradin, J. L., Du, S. and Jewell, D. E. (1997) The ratio of dietary (n-6) to (n-3) fatty acids in¯uences immune sistem function, eicosanoid metabolism, lipid peroxidation and vitamin E status in aged dogs. Journal of Nutrition 127, 1198±1205. Wayner, D. D. M., Burton, J. W., Ingold, K. U., Barclay, L. R. C. and Locke, S. J. (1987) The relative contributions of vitamin E, urate, ascorbate and proteins to the total peroxyl radicaltrapping antioxidant activity of human blood plasma. Biochimica et Biophysica Acta 924, 408± 419. Wulf, D. M., Morgan, J. B., Sanders, S. K., Tatum, J. B., Smith, G. C. and Williams, S. (1995) Eect of dietary supplementation of vitamin E on storage and caselife properties of lamb retail cuts. Journal of Animal Science 73, 399±405. Zaspel, J. B. and Csallany, S. (1983) Determination of alpha-tocopherol in tissue and plasma by high-performance liquid chromatography. Analytical Biochemistry 30, 146±150.
Eect of Dietary Vitamin E on the Oxidative Stability of Raw and Cooked Rabbit Meat C. Castellini,a* A. Dal Bosco,a M. Bernardinia & H. W. Cyrilb a
Istituto di Zootecnica Generale, FacoltaÁ di Agraria, UniversitaÁ di Perugia, Borgo XX Giugno 74, 06100 Perugia, Italy b Department of Animal Science, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka (Received 24 October 1997; revised version received 9 March 1998; accepted 12 March 1998)
ABSTRACT The eect of dietary a-tocopheryl acetate supplementation (200 mg/kg diet) on plasma and muscle levels of a-tocopherol and the oxidative stability of raw and cooked rabbit meat was determined. Two groups of 20 male hybrid rabbits were fed the experimental diets from 35 to 80 days of age. Feed intake, live weight, feed eciency and qualitative traits of the carcass and meat were recorded. The a-tocopherol levels in plasma and muscle were signi®cantly higher (p0.01) in the supplemented group, which also showed an increase in oxidative stability in both raw and cooked meat. The higher a-tocopherol level improved the physical traits of the meat, signi®cantly reducing shear value and increasing water-holding capacity; n-3 fatty acids in raw and cooked meat increased (p0.05) and the thrombogenic index decreased (p0.05). Dietary vitamin E did not in¯uence weight gain, feed intake and dressing yield. # 1998 Elsevier Science Ltd. All rights reserved
INTRODUCTION Rabbit meat is widely consumed in almost all of Europe (Italy, France, Spain, Portugal, Belgium and Hungary) as well as in other countries like the Ukraine, China and Russia where over 100 000 tonnes are consumed (Colin and Lebas, 1996). Rabbit meat has many positive dietetic characteristics for example low lipid and cholesterol levels and a high content of polyunsaturated fatty acids (PUFA), which can be further increased by speci®c dietary strategies (Castellini and Dal Bosco, 1998). Reported bene®ts of long-chain PUFA, mainly C20:5n3 and C22:6n3, on human health (Kinsella et al., 1990; Nettleton, 1991) have increased the interest in animal products with high levels of these acids (Hargis and Van Elswik, 1993; Nash et al., 1995). Unfortunately PUFA easily undergoes peroxidative damage during storage and cooking and as a consequence ¯avour, colour, texture and *To whom correspondence should be addressed. Fax: 00 39 75 585 3122; e-mail: [email protected] 153
154
C. Castellini et al.
nutritional value are decreased (Kanner et al., 1991) and atherogenic compounds can be generated (Addis and Park, 1989). The incorporation of antioxidants in the diet has shown favourable eects on meat characteristics of dierent species. Intake of vitamin E above the daily requirement increased a-tocopherol levels in plasma and tissues, improving lipid stability (Lin et al., 1989; Liu et al., 1995). In the rabbit protection against peroxide damage depends on vitamin E rather than on selenium (Cheeke, 1987) because the kidneys and liver have a high level of non-seleniumdependent glutatione peroxidase activity (Lee et al., 1979), hence the vitamin E requirement for rabbits is higher than for ruminants (Jenkins et al., 1970). Our previous ®ndings (Bernardini et al., 1996) demonstrated the positive role of vitamin E in protecting raw meat from peroxidation mainly in rabbits fed diets containing a small amount of ®sh meal. The aim of the present study was to con®rm these results and to check the eectiveness of supplemental dietary vitamin E in preventing the peroxidative processes in cooked meat. MATERIALS AND METHODS Animals and diets The study was carried out at the experimental rabbitry of the Animal Production Institute of the University of Perugia where the temperature was 18.53.1 C and the photoperiod was 16 h light/day. Forty hybrid males, weaned at 35 days, were divided into two homogeneous groups and fed ad libitum standard diets with 2% herring meal to enrich the long-chain n-3 fatty acids (>20 carbons) (Bernardini et al., 1996). The diet of group 1 was supplemented with a low level of a-tocopheryl acetate, (50 mg/kg diet, control) and that of group 2 with a high level of a-tocopheryl acetate (200 mg/kg supplemented). The ingredients and chemical composition of the diets are presented in Tables 1 and 2, respectively. TABLE 1 Ingredients of Rabbit Diet Ingredient Dehydrated alfalfa meal Barley meal Soyabean meal Fish meal Wheat straw Molasses CaCo3 Calcium diphosphate Ligninsulfunate Salt Coccidiostatic DL-methionine Vitamin±mineral premixa -tocopheryl acetate
% composition 40 31.5 18 2 4 0.8 1 0.6 0.5 0.5 versus 0.4985 0.06 0.04 1 0 versus 0.0015
Added per kg: vit. A 11 000 UI; vit. D3 2000 UI; vit. B1 2.5 mg; vit. B2 4 mg; vit. B6 1.25 mg; vit. B12 0.01 mg; -tocopheryl acetate 50 mg; biotine 0.06 mg; vit. K 2.5 mg; niacine 15 mg; folic acid 0.30 mg; d-panthotenic acid 10 mg; choline 600 mg; Mn 60 mg; Fe 50 mg; Zn 15 mg; 10.5 mg; Co 0.5 mg. a
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
155
TABLE 2 Chemical Composition and Nutrititional Value of the Diets Crude protein Ether extract Crude ®bre Ash N-free extract NDF-Neutral Detergent Fiber ADF-Acid Detergent Fiber ADL-Acid Detergent Liquid Hemicellulose Cellulose Digestible energy (estimated) -tocopherol
% dry matter " " " " " " " " " MJ/kg dry matter mg/kg
17.75 2.74 17.58 8.65 53.28 29.19 19.35 3.57 9.84 15.48 10.26 67 versus 263
Feed intake and live weight were recorded weekly and feed eciency was estimated as the ratio between consumption and weight gain. In vivo antioxidant capacity At 84 days of age, blood samples were drawn. The blood was collected over Na2ETDA (1±2 mg/ml blood) and immediately centrifuged (10 000 g for 10 min at 4 C). The supernatant was used for evaluating plasma antioxidant capacity expressed as total (Peroxil) radical-trapping antioxidant parameter (TRAP) (Miller et al., 1993). Slaughter, sample collection and physical analyses Rabbits were sacri®ced at 84 days of age. The drip loss was calculated as the dierence between the weight of hot and refrigerated carcasses (at 4 C for 24 hr), according to Blasco et al. (1993). From the refrigerated carcasses longissimus dorsi muscles were removed and carefully freed from connective and adipose tissues and a portion of them was used for chemical and physical analyses, (cooking loss, water-holding capacity, shear force and colour). Samples (622 cm) of about approximate 20 g were placed in open aluminium boxes and cooked for 15 min in an electric oven pre-heated to 200 C (Cyril et al., 1996). After cooking, the samples were dried with a paper towel. Total cooking loss was estimated on each sample cooled for 30 min to 15 C as the percentage ratio between cooked and raw weight. Water-holding capacity (WHC) was estimated, as indicated by Nakamura and Katoh (1985), by centrifuging 1 g of muscle for 4 min at 1500 g and determining the residual water by drying the sample at 70 C overnight. WHC was calculated as follows: WHC
weight after centrifugation ÿ weight after drying 100 initial weight
Shear force was evaluated on cores (1.25 2 cm) obtained from the mid-portions of the cooked samples by cutting them perpendicular to ®ber direction, using an Instron, model 1011, equipped with Warner-Blatzler meat shear apparatus. The colour parameters (L*, a*, b*) were evaluated using a tristimulus analyser (Minolta Chroma Meter CR-200) with the CIELAB Colour System (1976); from the chromaticity coordinates, hue and chroma were calculated.
156
C. Castellini et al.
Chemical analyses The chemical composition of the diets was analysed according to AOAC (1995), methods (1995). The -tocopherol level in diets, plasma and meat was determined by high performance liquid chromatography (Zaspel and Csallany, 1983). The fatty acids in the diets and meat were extracted according to Folch et al. (1957) and determined as methyl esters with a gas chromatograph using a DB wax capillary column (25 mm 1, 30 m length). Atherogenic and thrombogenic indices were calculated as indicated by Ulbricht and Southgate (1991). Lipid oxidation was assessed by the 2-thiobarbituric acid (TBARS) method (Ke et al., 1977) and expressed as mol malonaldehyde/kg tissue. Statistical analyses Statistical analyses were done using the following linear models [SAS/STAT (1990) GLM]: . Chemical composition of diets and in vivo parametersЮxed eect of diet (control versus supplemented); . Post-mortem itemsÐinteractive eect of diet and processing (raw versus cook meat). Statistical signi®cance of dierences were assessed by the t-test (SAS/GLM option PDIFF). RESULTS AND DISCUSSION -tocopherol level of diets The -tocopherol levels of the diets were 67 and 263 mg/kg diet (Table 2), indicating a good resistance of -tocopheryl acetate to feed processing (mixing and pelletting). Growing performance and plasma antioxidant capacity Productive performance was not signi®cantly aected by diet (Table 3). Only a slight reduction of feed intake (about 4 g/day) and a resulting lower weight gain (about 3 g/day) TABLE 3 Eect of -tocopheryl Acetate Supplementation on Productive Performance and Plasma Parameters Parameter
Slaughter weight Commercial carcass weight Dressing yield Weight gain Feed intake Feed eciency -tocopherol level Antioxidant capacity (TRAP) n=40; A,B = p0.01.
Treatment
g g % g/day g/day g/ml mol/l
Control
Supplemented
SE
2822.85 1752.85 62.14 38.29 140.16 3.69 1.56A 305.2A
2670.50 1676.28 62.73 35.12 136.24 3.92 4.67B 415.2B
305.66 199.40 1.55 5.54 7.06 0.59 1.65 51.0
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
157
were observed in supplemented animals; this is in agreement with previous ®ndings in beef (Arnold et al., 1993a). Autocatalytic peroxidation in muscle begins immediately after slaughter. The balance between pro-oxidative factors and antioxidant capacity aects the oxidative stability of tissues and consequently of meat (Buckley et al., 1995). In blood plasma there is a complex antioxidant system and although -tocopherol provides only a marginal contribution to TRAP (about 5±10%) it plays a speci®c role in trapping radicals directly and avoiding breakage of the fatty acid chain (Wayner et al., 1987). In our trial (Table 3) the plasma -tocopherol level increased signi®cantly (1.56 versus 4.67 g/ml; p0.01) according to the dietary level, which is in agreement with reports by other authors in other species (Bartov and Frigg, 1992; Arnold et al., 1993a). The plasma antioxidant capacity showed the same trend (305.2 versus 415.2 (mol/l; p0.01), con®rming our previous results (Bernardini et al., 1996). Physical characteristics, -tocopherol level and oxidative stability of raw and cooked meat Vitamin E supplementation signi®cantly (p0.05) reduced drip loss in the carcass (1.06 versus 1.56%) and shear force (4.53 versus 5.17 kg/cm2) in the cooked meat (Table 4). The positive eect on drip loss, although calculated dierently, has also been reported by Monahan et al. (1990) in pig and Mitsumoto et al. (1995) in beef. Asghar et al. (1989) suggested that -tocopherol preserves biomembranes and their ability to act as a semipermeable barrier, reducing the exudative loss (Stanley, 1991). In addition, Cheah et al. (1995) observed a positive eect of dietary vitamin E supplementation on drip loss and membrane stability. This eect is presumably due to the inhibition of phospholipase A2 activity, which consequently reduces the freeing of long-chain phospholipids from mitochondria and Ca++ release with a consequent decrease of post-mortem glycolysis and drip loss. As regards the weight loss a slightly higher value in the treated group was obtained, which is in agreement with Mitsumoto et al. (1995), who observed, in beef, that TABLE 4 Eect of -tocopheryl Acetate on Physical Traits of Raw and Cooked Meat, on of -tocopherol level and TBARS Parameter
Moisture Drip loss of carcass Shear value WHC Cooking loss
Raw
%. % kg/cm2 % %
Colour L* a* b* hue chroma -tocopherol level TBARS
/g mol/ MDA/kg
n=80; A,B: p0.01; a,b: p0.05.
Cooked
SE
Control
Supplement
Control
Supplement
75.58A 1.56b 3.21a 57.11b Ð
76.94B 1.06a 2.95a 58.98c Ð
52.36 Ð 5.17c 48.98a 30.72
52.13 Ð 4.53b 50.02a 32.25
1.05 0.32 1.09 1.15 1.48
58.65A 5.53B 0.85A 0.25A 5.62A 1.14A 1.34b
60.72A 5.17B 1.09A 0.18A 5.63A 3.51B 0.71a
80.13B 3.97A 10.67B 1.21B 11.40B 1.08A 9.33B
81.32B 3.78A 9.52B 1.17B 10.30B 3.11B 3.45A
2.30 0.56 2.38 0.08 2.27 0.15 1.19
158
C. Castellini et al.
dietary vitamin E supplementation shifted weight loss from drip loss to cooking loss. As previously stated, supplementation presumably aected the integrity of the muscle ®ber, and consequently the moisture (p0.01) and WHC (p0.05) of the fresh muscle increased. Colour parameters did not show variations ascribable to the diet. Faustman et al. (1989) reported that the eect of vitamin E on the level of metmyoglobin, which causes the brown pigmentation of meat, was evident after some days of storage, while after 24 h only a light decrease of a* (red index) appeared in treated animals. It is also possible that in rabbit meat the oxidative processes are slower and less manifest because of the low amount of myoglobin. The -tocopherol level in raw muscle (Table 4) was signi®cantly higher (3.51 versus 1.14 g/g; p0.01) on increasing the dietary level to 200 mg/kg, in agreement with reports in rabbit (Lopez-Bote et al., 1997), poultry (Sklan et al., 1983), pig (Monahan et al., 1990) and beef (Arnold et al., 1993b; Liu et al., 1994). The level of -tocopherol was not reduced by cooking, as also reported by Liu et al. (1994), con®rming that vitamin E withstands heating (Machlin, 1984) and thus performs as an antioxidant also in cooked products (Faustman et al., 1989). This fact has positive implications in human nutrition because vitamin E, besides the speci®c protection of n-3 fatty acids, reduces cholesterol oxidation and therefore its cytotoxicity and atherogenecity (Kumar and Singhal, 1991). The oxidative processes in muscle are negatively correlated with -tocopherol level; the lowering of TBARS is equal to 47% in fresh meat and 63% in cooked meat. TBARS values in fresh muscle agree with those obtained in rabbit by Lopez-Bote et al. (1997) and in other animal species by Tsai et al. (1978) and Wulf et al. (1995). For cooked meat, our TBARS values are higher than those reported in beef and pig (Monahan et al., 1990; Liu et al., 1994). Furthermore, the positive eect of supplementation was more evident in our trial. According to Allen and Foegeding (1981), one of the most important factors aecting lipid oxidation in muscle is the PUFA content. The high PUFA level of rabbit meat probably activates more intense peroxidative processes; in these conditions the eectiveness of vitamin E could be greater. Fatty acid composition of meat Supplementary -tocopheryl acetate signi®cantly increased the n-3 fatty acid level (Table 5), both in raw (+14.1%) and in cooked meat (+37.6%). Tsai et al. (1978) did not observe, in swine, variations either in the fatty acid distribution or in the amount of unsaturation, but the authors did not analyse the long-chain PUFA, which in our trial contributed to making the dierences consistent. Lopez-Bote et al. (1997) did not observe any signi®cant eect of vitamin E supplementation on the fatty acid pro®le of rabbit in polar and neutral lipids. This disagreement is probably due to the presence of herring meal in our diets, which enhanced the protective eect of -tocopherol. The atherogenic index did not show signi®cant variations, while the trombogenic index was lower in supplemented animals with the higher n-3 level. It is concluded that -tocopheryl acetate supplementation was eective in increasing vitamin E and n-3 PUFA in raw and cooked meat, and in reducing the thrombogenic index, with consequent bene®ts on the nutritional quality for consumers. In fact, an increased intake of n3 fatty acids without adequate antioxidant protection could result in increased free radicals and lipid oxidative by-products (Wander et al., 1997). In this context, the supplementation of 200 mg/kg vitamin E provides a very dietetic meat, rich in n-3 and adequately protected. Further research is needed to ascertain the vitamin E dose with respect to duration of administration, and the eventual synergy between vitamin E and vitamin C in protecting the meat from oxidative processes during cooking and storage.
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
159
TABLE 5 Eect of -tocopheryl Acetate on Fatty Acid Composition (g per 100 g) in Raw and Cooked Meat Fatty acid
C8:0 C10:0 C12:0 C14:0 C14:1n6 C15:0 C16:0 C16:1n7 C17:0 C18:0 C18:1n9 C18:2n6 C18:3n6 C18:3n3 C18:4n3 C20:1n6 C20:2n6 C20:3n6 C20:4n6 C20:3n3 C20:5n3 C21:5n3 C22:5n3 C22:6n3 C24:0 C24:1 SFA MUFA PUFA n-3 Atherog. index Tromb. index
Raw
Cooked
Control
Supplement
Control
Supplement
0.55 0.42 0.44 3.25 0.45 0.76 27.77a 3.61 0.65 5.81 20.75 25.33b 0.17 2.64 0.96A 0.10 0.12a 0.36 3.83 0.04 0.18A 0.05A 0.48 0.75a 0.15a 0.38 39.80 25.30 34.90b 5.10b 0.68 0.86b
0.45 0.44 0.60 3.62 0.49 0.81 28.49a 4.11 0.73 4.47 19.74 24.61b 0.17 2.55 1.42A 0.12 0.11a 0.41 3.85 0.06 0.29B 0.15B 0.49 0.96b 0.28b 0.58 39.91 25.04 35.05b 5.92c 0.70 0.80a
0.65 0.60 0.61 3.56 0.45 0.87 30.56b 3.40 0.74 5.31 20.15 23.27ab 0.11 2.72 0.83A 0.10 0.20b 0.35 3.81 0.05 0.12A 0.17B 0.11 0.63a 0.15a 0.48 43.05 24.58 32.37a 4.63a 0.79 0.97c
0.41 0.47 0.49 3.63 0.46 0.83 30.35b 3.85 0.66 5.31 20.20 22.41a 0.02 2.45 1.27B 0.13 0.22b 0.57 3.48 0.03 0.26B 0.23B 0.34 0.79a 0.27b 0.47 42.42 25.11 32.43a 5.37b 0.78 0.87b
SE 0.43 0.35 0.24 0.73 0.15 0.10 2.65 1.24 0.07 2.11 2.45 2.59 0.09 0.46 0.68 0.09 0.06 0.58 0.95 0.05 0.07 0.06 0.24 0.26 0.06 0.15 3.41 3.01 2.99 0.67 0.11 0.10
n=80; A,B = p0.01; a,b,c = p0.05.
ACKNOWLEDGEMENT Research supported by the National Research Council of Italy. Special Project RAISA. Sub-Project no. 3. Paper no. 2984. REFERENCES Addis, P. B. and Park, S. W. (1989) Role of lipid oxidation products in atherosclerosis. In: Food Toxicology, a perspective on the relative risk, eds. S. Raylor and R. Scanalan, pp. 297±330. Marcel Dekker, New York. Allen, C. E. and Foegeding, E. A. (1981) Some lipid characteristics and interactions in muscle foods. A review. Food Technology 35, 253±257.
160
C. Castellini et al.
AOAC (1995). Ocial Methods of Analysis. 15th Edn. Association of Ocial Analytical Chemists, Washington. Arnold, R. N., Scheller, K. K., Arp, S. C., Williams, S. N. and Shaefer, D. M. (1993a) Dietary atocopheryl acetate enhances beef quality in Holstein and beef breed steers. Journal of Food Science 58, 28±33. Arnold, R. N., Arp, S. C., Scheller, K. K., Williams, S. N. and Shaefer, D. M. (1993b) Tissue equilibration and subcellular distribution of vitamin E relative to myoglobin and oxidation in displayed beef. Journal of Animal Science 71, 105±118. Asghar, A., Lin, C. F., Gray, J. I., Buckley, D. J., Booren, A. M., Crackel, R. L. and Flegal, C. J. (1989) In¯uence of oxidised oil and antioxidant supplementation on membrane bound lipid stability in broiler meat. British Poultry Science 30, 815±823. Bartov, I. and Frigg, M. (1992) Eect of high concentrations of dietary vitamin E during various age periods on performance, plasma vitamin E and meat stability of broiler chicks at 7 weeks of age. British Poultry Science 33, 393±402. Bernardini, M., Dal Bosco, A., Castellini, C. and Miggiano, G. (1996) Dietary vitamin E supplementation: antioxidant capacity and meat quality. Proceedings of the 6th World Rabbit Congress, 3, 137±140. Blasco, A., Ouhayoun, J. and Masoero, G. (1993) Harmonization of criteria terminology in rabbit meat research. World Rabbit Science 1, 3±10. Buckley, D. J., Morrissey, P. A. and Gray, J. I. (1995) In¯uence of dietary vitamin E on the oxidative stability of pig meat. Journal of Animal Science 73, 3122±3130. Castellini, C. and Dal Bosco, A. (1998) Eect of dietary herring meal on the omega-3 content of rabbit meat. Proceedings in Food and Health, Elsevier, pp. 67±71. Cheah, K. S., Cheah, A. M. and Krausgrill, D. I. (1995) Eect of dietary supplementation of vitamin E on pig meat quality. Meat Science 39, 255±263. Cheeke, P. R. (1987) Vitamins. In Rabbit Feeding and Nutrition, ed. T. J. Cunha. Vol. 9, pp. 145± 147. Gainesville, Florida. Academic Press, London. CIELAB Colour System (1976) Commission International de l'Eclairage. CIE, Publcation 36, Paris. Colin, M. and Lebas, F. (1996) Rabbit meat production in the world. A proposal for every country. Proceedings of the 6th World Rabbit Congress, 3, 323±330. Cyril, H. W., Castellini, C. and Dal Bosco, A. (1996) Comparison of three cooking methods of rabbit meat. Italian Journal of Food Science 8, 337±340. Faustman, C., Cassens, R. G., Schaefer, D. M., Buege, D. R., Williams, S. N. and Scheller, K. K. (1989) Improvement of pigment and lipid stability in Holstein steer beef by dietary supplementation with vitamin E. Journal of Food Science 54, 858±867. Folch, J., Lees, M. and Sloane-Stanley, H. (1957) A simple method for the isolation and puri®cation of total lipids from animal tissues. Journal of Biology and Chemistry 226, 497±509. Hargis, P. S. and Van Elswik, M. E. (1993) Manipulating the fatty acid composition of poultry meat and eggs for the health conscious consumer. World's Poultry Science Journal 49, 251±264. Jenkins, K. L., Hidiroglou, M., MacKay, R. R. and Proulx, J. G. (1970) In¯uence of selenium and linoleic acid on the development of nutritional muscolar dystrophy in beef calves, lambs and rabbits. Canadian Journal of Animal Science 50, 137±146. Kanner, J., Harel, S. and Granit, R. (1991) Oxidative processes in meat and meat products: quality implications. Meat Science 36, 169±189. Ke, P. J., Ackman, R. G., Linke, B. H. and Nash, D. M. (1977) Dierential lipid oxidation products in various parts of frozen mackerel. Journal of Food Technology 12, 37±47. Kinsella, J. E., Lokesh, B. and Stone, R. A. (1990) Dietary n-3 polyunsaturated fatty acids and amelioration of cardiovascular disease: possible mechanism. American Journal of Clinical Nutrition 52, 1±28. Kumar, N. and Singhal, O. P. (1991) Cholesterol oxides and atherosclerosis: a review. Journal of Science of Food Agriculture 55, 497±512. Lee, Y. H., Layman, D. K. and Bell, R. R. (1979) Selenium-dependent and non selenium-dependent glutathione peroxidase activity in rabbit tissue. Nutrition Reproduction International 20, 573±578. Lin, C. F., Asghar, A., Gray, J. I., Buckley, D. J., Booren, A. M., Crackel, R. L. and Flegal, C. J. (1989) Eects of oxidised dietary oil and antioxidant supplementation on broiler growth and meat stability. British Poultry Science 30, 855±864.
Eect of Dietary Vitamin E on the Oxidative Stability of Rabbit Meat
161
Liu, Q., Scheller, K. K., Schaefer, D. M., Arp, S. C. and Williams, S. N. (1994) Dietary a-tocopheryl acetate contribute to lipid stability in cooked beef. Journal of Food Science 59, 288±290. Liu, Q., Lanari, M. C. and Schaefer, D. M. (1995) A review of dietary vitamin E supplementation for improvement of beef quality. Journal of Animal Science 73, 3131±3140. Lopez-Bote, C. J., Rey, A. I., Sanz, J. I. and Gray, J. I. (1997) Dietary vegetable oils and a-tocopherol reduce lipid oxidation in rabbit muscle. Journal of Nutrition 127, 1176±1182. Machlin, L. J. (1984) Vitamin E. In Handbook of Vitamins: Nutritional, Biochemical and Clinical Aspects, ed. L. Machlin pp. 99±145. Marcel Dekker, New York. Miller, N. J., Rice-Evans, C., Davies, M. J., Gopinathan, V. and Milner, A. (1993) A novel method for measuring antioxidant capacity and its application to monitoring the antioxidant status in premature neonates. Clinical Science 84, 407±412. Mitsumoto, M., Arnold, R. N., Schaefer, D. M. and Cassens, R. G. (1995) Dietary vitamin supplementation shifted weight loss from drip to cooking loss in fresh beef longissimus during display. Journal of Animal Science 73, 2289±2294. Monahan, F. J., Buckley, D. J., Gray, J. I. and Morrissey, P. A. (1990) Eect of dietary vitamin E on the stability of raw and cooked pork. Meat Science 27, 99±108. Nakamura, M. and Katoh, K. (1985) In¯uence of thawing method on several properties of rabbit meat. Bulletin of Ishikawa Prefecture College of Agriculture, Japan 11, 45±49. Nash, D. M., Hamilton, R. M. G. and Hulan, H. W. (1995) The eect of dietary herring meal on the omega-3 fatty acid content of plasma and egg yolk lipids of laying hens. Canadian Journal of Animal Science 2, 247±253. Nettleton, J. A. (1991) n-3 fatty acids: comparison of plant and seafood sources in human nutrition. Journal of American Dietetic Association 91, 331±337. SAS/STAT (1990) User's guide, Version 6, Cary, NC. Sklan, D., Tenne, Z. and Budowski, P. (1983) The eect of dietary fat and tocopherol on lipolysis and oxidation in turkey meat stored at dierent temperatures. Poultry Science 62, 2017±2021. Stanley, D. W. (1991) Biological membrane deterioration and associated quality losses in food tissues. Critical Review of Food Nutrition 30, 487±495. Tsai, T. C., Wellington, G. H. and Pond, W. G. (1978) Improvement in the oxidative stability of pork by dietary supplementation of swine rations. Journal of Food Science 43, 193±196. Ulbricht, T. L. V. and Southgate, D. A. T. (1991) Coronary heart disease: seven dietary factors. The Lancet 338, 985±990. Wander, R. C., Hall, J. A., Gradin, J. L., Du, S. and Jewell, D. E. (1997) The ratio of dietary (n-6) to (n-3) fatty acids in¯uences immune sistem function, eicosanoid metabolism, lipid peroxidation and vitamin E status in aged dogs. Journal of Nutrition 127, 1198±1205. Wayner, D. D. M., Burton, J. W., Ingold, K. U., Barclay, L. R. C. and Locke, S. J. (1987) The relative contributions of vitamin E, urate, ascorbate and proteins to the total peroxyl radicaltrapping antioxidant activity of human blood plasma. Biochimica et Biophysica Acta 924, 408± 419. Wulf, D. M., Morgan, J. B., Sanders, S. K., Tatum, J. B., Smith, G. C. and Williams, S. (1995) Eect of dietary supplementation of vitamin E on storage and caselife properties of lamb retail cuts. Journal of Animal Science 73, 399±405. Zaspel, J. B. and Csallany, S. (1983) Determination of alpha-tocopherol in tissue and plasma by high-performance liquid chromatography. Analytical Biochemistry 30, 146±150.