- Email: [email protected]
The effects of dietary α-tocopheryl acetate supplementation and modified atmosphere packaging (MAP) on the quality of lamb patties
Meat Science 56 (2000) 61±66
www.elsevier.com/locate/meatsci
The eects of dietary a-tocopheryl acetate supplementation and modi®ed atmosphere packaging (MAP) on the quality of lamb patties J.P. Kerry a,*, M.G. O'Sullivan a, D.J. Buckley a, P.B. Lynch b, P.A. Morrissey a a
Department of Food Science and Technology, University College Cork Ð National University of Ireland, Cork, Ireland b Teagasc, Moorepark, Fermoy, Co. Cork, Ireland Received 3 July 1998; received in revised form 5 January 2000; accepted 26 January 2000
Abstract The eects of dietary a-tocopheryl acetate supplementation and/or packaging on the quality of lamb patties were investigated. Ewes (n=12) were selected and scanned to assess pregnancy. They were divided into two groups (n=6). The control group was fed a non-supplemented diet of 20 mg a-tocopheryl acetate/kg feed/day for 9 weeks ante-parturition and 3 weeks post-parturition. The lambs were weaned at 3 weeks and fed either the non-supplemented or supplemented diet for 10 weeks prior to slaughter. The M. longissimus dorsi from each carcass from each dietary group was stored at ÿ20 C for 7 months. Patties were formed from supplemented or control minced m. longissimus dorsi and held in either modi®ed atmosphere packs (MAP) under atmospheres of 70:30, 80:20 or 90:10 CO2:O2, under vacuum or in overwrapped trays. All packs were held under refrigerated (4 C, 616 lux) display for a period of 10 days. Patties were assessed for oxidative and colour stability on days 0, 2, 4, 6, 8 and 10. With each type of pack, dietary a-tocopheryl acetate supplementation signi®cantly increased oxidative and colour stability compared to control patties. As oxygen concentrations increased in MAP packs, colour stability was enhanced but the rate of lipid oxidation increased. Vacuum packaged patties had signi®cantly (P<0.05) higher Hunter `a' values, lower proportions of metmyoglobin and lower TBARS numbers than those held under all other forms of packaging. Aerobically packaged patties had lower Hunter `a' values, higher proportions of metmyoglobin and lower TBARS numbers compared to MAP patties. # 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction The three sensory properties by which consumers most readily judge meat quality are appearance, texture and ¯avour (Liu, Lanari & Schaefer, 1995). At the point of sale, colour and colour stability are the most important attributes of meat quality and various approaches have been used to meet consumer expectation that an attractive, bright-red colour indicates a long shelf-life and good eating quality (Hood & Mead, 1993). In red meats, consumers relate the bright red colour to freshness, while discriminating against meat which has turned brown in colour (Morrissey, Buckley, Sheehy & Monahan, 1994). The loss of the bright red colour is caused by the oxidation of the red oxymyoglobin to the * Corresponding author. Tel.: +353-21-902256; fax: +353-21276318. E-mail address: [email protected] (J.P. Kerry).
undesirable brown metmyoglobin (Faustman & Cassens, 1990). Discolouration in retail meats during display conditions may occur as a combined function of muscle pigment oxidation (oxymyoglobin to metmyoglobin) and lipid oxidation in membrane phospholipids (Sherbeck, Wolf, Morgan, Tatum, Smith & Williams, 1995). The rate of colour loss in fresh meat is dependent on the temperature of storage (Renerre, 1990). Low storage temperature combined with high oxygen tension or the exclusion of air are the preferred methods of preserving fresh meat colour (Gill, 1996). Modi®ed atmosphere packs (MAP) are becoming popular with retailers for packaging fresh meat cuts. The evolution of MAP for fresh meat has also occurred in response to the need for de®ned packaging environments related to the properties of meat from dierent species and the need to satisfy speci®c marketing requirements (Hood & Mead, 1993). It is now widely accepted that dietary supplementation with a-tocopheryl acetate eectively controls lipid
0309-1740/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(00)00021-8
62
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
oxidation and colour deterioration in red meats like lamb (Guidera, Kerry, Buckley, Lynch & Morrissey, 1997a,b) and beef (Sherbeck et al., 1995). While a number of studies have investigated the relationship between lamb quality and MAP (Doherty, Sheridan, Allen, McDowell & Blair, 1997) and the eects of dietary vitamin E supplementation on colour and oxidative stability in lamb (Guidera et al., 1997a,b; Strohecker, Faustman, Furr, Hoagland & Williams, 1997), only a limited number of studies have been reported on the eects of vitamin E supplementation and MAP on red meat quality (Formanek, Kerry, Buckley, Morrissey & Farkas, 1998; Kerry, Burkley, O'Sullivan, Lynch, Buckley & Morrissey, 1996; Lanari, Schaefer, Cassens & Scheller, 1995a; Lanari, Schaefer & Scheller, 1995b). The aim of this study was to examine the eects of dietary a-tocopheryl acetate supplementation, the use of MAP in relation to other forms of packaging and the eects of storage time, on a-tocopherol content, oxidative properties, colour and overall keeping quality of lamb patties, held under refrigerated (4 C) display. 2. Materials and methods 2.1. Chemicals All chemicals were of AnalaR grade and obtained from the British Drug House, Poole, Dorset, UK; Sigma Chemical Co. Ltd., Poole, Dorset, UK and Rathburn Chemical Co. Ltd., Walkerburn, Peableshire, Scotland, UK. a-Tocopheryl acetate was obtained from Roche Products Ltd., Welwyn, Garden City, Hertfordshire, UK. 2.2. Animals and diet Twelve CheviotBorder Leicester ewes, scanned to assess that they were pregnant with twins, were randomly assigned to two groups (n=6) which were fed diets containing 20 (non-supplemented) and 1000 (supplemented) mg a-tocopheryl acetate/kg feed/day for 9 weeks prior and 3 weeks post-parturition. Lambs remained on the same level of supplementation as their mothers throughout the experiment. Lambs were slaughtered 13 weeks post-parturition. The conditions of housing and diets of both ewes and lambs have been reported previously (Guidera et al., 1997a). 2.3. Sampling and analysis After slaughter and evisceration, the lamb carcasses were chilled overnight, then the m. longissimus dorsi was removed from each carcass, vacuum-packed and stored at ÿ20 C for 7 months. Frozen m. longissimus dorsi was thawed (4 C for 12 h) and minced using a MAINCA
rust-free steel meat mincer (MAINCA, C/Jaume Ferran s/n, Granollers, Barcelona, Spain) through a plate diameter of 5 mm into plastic bags. Patties (80 g) were formed from both supplemented and non-supplemented lamb meat prior to packaging. 2.4. Packaging and storage conditions Lamb patties were placed on polystyrene/EVOH/ polyethylene trays and overwrapped with oxygen permeable (6000±8000 cm3/m2/24 h at STP) polyvinylchloride ®lm (Wrap Film Systems Ltd., Shropshire, UK) for aerobic packaging, or heat-sealed within these trays to create headspace using a low oxygen permeable (8±12 cm3/m2/24 h at STP) polyester-EVOH-polyethylene ®lm (Boss Packaging Ltd., Bad Homburg, Germany) for MAP using packing machine type: VS 100 BS (Gustav MuÈller and Co., Zum Wingert 5, 6380 Bad Homburg 6, Germany). The gas mixtures used for MAP were 70:30, 80:20 or 90:10 oxygen:carbon dioxide. Patties were vacuum-packaged using a Webomatic type: D463 (Webomatic Vacuum Packaging Systems, Werner Bonk, Mausegatt 59, D 463 Bochum 6, Germany) vacuum packer. The vacuum packaging material consisted of Cryovac polyamide/polyethylene 20/70 low oxygen permeable multi¯ex ®lms (Cryovac, W.R. Grace Europe Inc., Av. Montchoisi 35, 1001 Lausanne, Switzerland) (45 cm3/m2/24 h at STP). Patties were displayed for up to 10 days at 4 C under ¯uorescent light (616 lux). 2.5. -Tocopherol determination The a-tocopherol contents of m. longissimus dorsi from supplemented or non-supplemented lamb were determined in lamb meat after slaughter, after thawing and mincing previously frozen (ÿ20 C for 7 months) primal cuts and from patties held under dierent packaging conditions. a-Tocopherol in minced lamb was extracted using the method of Sheehy, Morrissey and Flynn (1993) and quanti®ed by HPLC using a Waters model S10 pump, a Waters 717 autosampler, a Machery-Nagel Nucleosil 5 C18 (2500.4 mm) reverse phase column and a Waters model 486 UV±visible wavelength detector (Millipore Corporation, Milford, MA 01757, USA) set at 292 nm. The mobile phase was methanol:water (97:3) at a ¯ow rate of 2 ml/min. Data were recorded and evaluated using a Millipore Millenium 2010 chromatography management system (Millipore Corporation, Milford, MA 01757, USA). 2.6. Determination of lipid oxidation Lipid oxidation was assessed by the 2-thiobarbituric acid method (TBARS) (Ke, Ackman, Linke & Nash, 1977) and expressed as mg malonaldehyde/kg muscle.
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
63
2.7. Colour analysis
3.2. Colour stability of lamb patties
Hunter L, a, b values were determined using a Minolta Chromameter CR-300 (Minolta Camera Co., Osaka, Japan). Colour readings were measured by placing the calibrated hand held probe of the Minolta Chromameter in contact with the overwrapped patties. Metmyoglobin formation (Krzywicki, 1979) was also determined in these samples using a Perkin-Elmer (Lambda 2) spectrophotometer (Perkin-Elmer Corporation, Norwalk, CI, USA).
3.2.1. Hunter 'a' values The eects of dietary a-tocopheryl acetate supplementation on Hunter 'a' values of lamb patties for various packaging systems are shown in Fig. 1. Hunter 'L' and 'b' values showed no overall trends during storage. Higher Hunter 'a' values were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs from days 2 to 6 (P<0.01) and days 8 to 10 (P<0.05), aerobically on days 2 (P<0.01) and day 4 (P<0.05) and under vacuum on d 2 (P<0.05). Both supplemented and nonsupplemented lamb patties packaged under vacuum had higher Hunter 'a' values compared to all other packaging systems and these dierences were signi®cant on day 4 (P<0.05) and days 6 to 10 (P<0.01). Supplemented lamb patties packaged in MAP packs had signi®cantly (P<0.05) higher Hunter 'a' values than patties held in aerobic packaging from day 2 to 6. Nonsupplemented lamb patties held in aerobic packs had the lowest Hunter 'a' values of all meat samples on day 2 and 4. These values were signi®cantly lower than nonsupplemented patties held in MAP packs. However, on day 6, Hunter 'a' values for 90:10 O2:CO2 were signi®cantly (P < 0.05) lower than those for aerobically packaged or other MAP non-supplemented patties. By day 10, all non-supplemented patties held in MAP had signi®cantly (P<0.05) lower Hunter 'a' values than aerobically packaged or supplemented patties held
2.8. Statistical analysis Comparisons between dietary treatments for a-tocopherol levels were tested using Student's t-test. ANOVA repeated analysis of variance was performed on data obtained from the oxidative and colour analysis of patties using the statistical package SPSS (SPSS Ltd., West St, Woking, Surrey, UK). 3. Results and Discussion 3.1. -Tocopherol levels in lamb meat a-Tocopherol concentrations were higher (P<0.05) in supplemented (5.30.3 mg/g muscle) than non-supplemented (0.80.2 mg/g muscle) m. longissimus dorsi. A signi®cant (P<0.001) decrease from 5.30.3 to 2.90.1 mg a-tocopherol/g muscle was observed in minced supplemented m. longissimus dorsi after frozen storage at ÿ20 C for 7 months. These results are in agreement with those reported by Guidera et al. (1997a). The a-tocopherol levels in non-supplemented lamb meat held in vacuum packs, aerobically or in 70:30, 80:20 or 90:10 O2:CO2 MAP packs after 10 days were 0.60.1, 0.50.1, 0.10.0, 0.10.1 and 0.10.1 mg/g meat, respectively. a-Tocopherol levels present in supplemented m. longissimus dorsi patties held in vacuum packs, aerobically or in 70:30, 80:20 and 90:10 O2:CO2 MAP packs after 10 days were 2.90.1, 2.60.3, 1.50.2, 1.20.1 and 0.80.1 mg/g meat, respectively. The decreases in a-tocopherol levels in both supplemented and non-supplemented lamb meat held under MAP were signi®cant (P<0.05) in all cases. These results have not been presented for lamb previously but are in agreement with those reported by Formanek et al. (1998) for a-tocopheryl acetate supplemented beef held under MAP conditions. They reported that over time, greater reductions in minced beef atocopherol levels occurred as oxygen concentrations increased within packs. Formanek et al. (1998). suggested that as oxygen concentrations increased within packs, an increase in the oxygen reactive species also occurred, thereby consuming a-tocopherol.
Fig. 1. Eect of dietary a-tocopheryl acetate and packaging on Hunter 'a' values in lamb patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. Hunter 'a' values in lamb patties from the nonsupplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2, (~,~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
64
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
under MAP conditions. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a, 1997b), Strohecker et al. (1997) and Wulf, Morgan, Sanders, Tatum, Smith and Williams (1995). However, as indicated above, no information is available regarding the use of dietary atocopheryl acetate supplemented lamb in relation to colour stability in various packaging systems. Lanari et al. (1995a) did observe that MAP increased colour stability in frozen beef when compared to aerobically packaged samples. They also found that the colour stability of MAP frozen beef samples was signi®cantly enhanced by a-tocopheryl acetate supplementation. Similar results were also reported by Kerry et al. (1996) for fresh beef samples following a-tocopheryl acetate supplementation. Therefore, it would appear that overall colour trends reported for studies investigating the eects of a-tocopheryl acetate supplementation and packaging on beef quality are in agreement with the data presented here for lamb. 3.2.2. Metmyoglobin formation The eects of dietary a-tocopheryl acetate supplementation on metmyoglobin formation in lamb patties held in various packaging systems are shown in Fig. 2. Lower proportions of metmyoglobin were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs on days 2 and 4 (P<0.01) and days 6 (P<0.05), aerobically on
Fig. 2. Eect of dietary a-tocopheryl acetate and packaging on metmyoglobin formation in patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. Metmyoglobin formation in lamb patties from the non-supplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2, (~, ~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
days 2 and 4 (P<0.01) and day 6 (P<0.05). No signi®cant dierences were observed between supplemented and non-supplemented lamb patties held in vacuum packs. Both supplemented and non-supplemented lamb patties packaged under vacuum had lower proportions of metmyoglobin compared to all other packaging systems and these dierences were signi®cant on days 2 to 10 (P<0.01). Supplemented lamb patties packaged in MAP packs had signi®cantly (P<0.05) lower proportions of metmyoglobin than patties held in aerobic packaging from days 2 to 6. Non-supplemented lamb patties held in aerobic packs had the highest proportions of metmyoglobin of all meat samples on days 2 and 4. These values were signi®cantly (P<0.05) higher than non-supplemented patties held in MAP packs on day 2. On days 8 and 10, no signi®cant dierences were observed between supplemented or non-supplemented lamb patties held in aerobic or MAP conditions. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a,1997b), Strohecker et al. (1997) and Wulf et al. (1995). However, no information is available regarding the use of dietary a-tocopheryl acetate supplemented lamb in relation to metmyoglobin development in various packaging systems. In beef studies, Taylor, Down and Shaw (1990) and Gill and Jones (1994) found that a lower percentage of metmyoglobin was detected in vacuum-packed beef than in MAP packaged samples during storage. These ®ndings support those presented for lamb in this study. Kerry et al. (1996) found that metmyoglobin formation in beef steak cores packaged under MAP and air increased at the same rate over 10 days of refrigerated display. However, these authors also found that metmyoglobin formation was reduced in all packs, particularly MAP (80:20, O2:CO2), when atocopheryl acetate supplemented beef was assessed. The combination eect of a-tocopheryl acetate supplementation and packaging type was also observed for lamb in this study. 3.2.3. Oxidative stability of lipids in lamb patties The eect of dietary a-tocopheryl acetate supplementation on TBARS values in lamb patties held in various packaging systems are shown in Fig. 3. Lower TBARS values were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs on days 2 to 10 (P<0.01), aerobically on days 2 to 10 (P<0.01) and under vacuum on days 8 and 10 (P<0.05). In general, both supplemented and non-supplemented lamb patties packaged under vacuum had lower TBARS values compared to other packaging systems. These dierences were signi®cant on days 2 to 10 for supplemented lamb patties and from days 4 to 8 (P<0.05) for non-supplemented lamb patties.
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
65
beef steaks and steak cores from cattle fed a control diet. However, this detrimental eect was oset or reduced by a-tocopheryl acetate supplementation. Similar to the results presented in this study, Formanek et al. (1998) reported that TBARS values in a-tocopheryl acetate supplemented minced beef were reduced in aerobic, vacuum and MAP packs compared to non-supplemented beef following refrigerated storage for 10 days. Similarly, these authors also showed that TBARS values increased in minced beef as oxygen levels increased in MAP packs and that vacuum packing was most eective in controlling the development of lipid oxidation. Acknowledgements Fig. 3. Eect of dietary a-tocopheryl acetate and packaging on the oxidative stability (TBARS) in lamb patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. TBARS from lamb patties from the non-supplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2 (~,~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
Supplemented lamb patties packaged in 70:30, O2:CO2 and 80:20, O2:CO2 MAP had equivalent TBARS values to those of aerobically packaged samples. Supplemented lamb patties held in 90:10, O2:CO2 MAP had signi®cantly (P<0.05) higher TBARS values than either aerobically packaged or 70:30, O2:CO2 and 80:20, O2:CO2 MAP samples. Non-supplemented lamb patties held in aerobic packs had higher TBARS values compared to supplemented lamb patties held in 90:10, O2:CO2 MAP from days 6 to 10 (P<0.05) and 70:30, O2:CO2 and 80:20, O2:CO2 MAP from days 2 to 10 (P<0.05). The highest TBARS values were determined for non-supplemented lamb patties packaged in all three MAP atmospheres and these were signi®cantly (P<0.01) higher than levels determined for other packaging systems from days 4 to 10. Non-supplemented patties packaged in 90:10, O2:CO2 MAP had signi®cantly (P<0.05) higher TBARS values than patties held in either 70:30, O2:CO2 or 80:20, O2:CO2 MAP atmospheres. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a,1997b), Strohecker et al. (1997) and Wulf et al. (1995). However, no information is available regarding the use of dietary a-tocopheryl acetate supplemented lamb in relation to oxidative stability in various packaging systems. However, similar results to those reported in this paper have been presented for beef. Kerry et al. (1996) found that MAP promoted lipid oxidation in
We would like to thank Homann-La Roche, Basel, Switzerland for the funding of this work. References Doherty, A. M., Sheridan, J. J., Allen, P., McDowell, D. A., & Blair, I. S. (1996). Physical characteristics of lamb primals packaged under vacuum or modi®ed atmospheres. Meat Science, 42, 315±324. Faustman, C., & Cassens, R. G. (1990). In¯uence of aerobic metmyoglobin reducing capacity on colour stability of beef. Journal of Food Science, 55, 1279±1283. Formanek, Z., Kerry, J. P., Buckley, D. J., Morrissey, P. A. & Farkas, J. (1998). Eects of dietary vitamin E supplementation and packaging on the quality of minced beef. Meat Science, 50, 203±210. Gill, C. O. (1996). Extending the storage life of raw chilled meats. Meat Science, 43, S99±S109. Gill, C. O., & Jones, T. (1994). The display of retail packs of ground beef after their storage in master packages under various atmospheres. Meat Science, 37, 281±295. Guidera, J., Kerry, J. P., Buckley, D. J., Lynch, P. B., & Morrissey, P. A. (1997a). The eect of dietary vitamin E supplementation on the quality of fresh and frozen lamb meat. Meat Science, 45, 33±43. Guidera, J., Kerry, J. P., Buckley, D. J., Lynch, P. B., & Morrissey, P. A. (1997b). The eect of dietary a-tocopheryl acetate supplementation on muscle a-tocopherol levels and lamb quality. Irish Journal of Agricultural and Food Research, 36, 241±247. Hood, D. E., & Mead, G. C. (1993). Modi®ed atmosphere storage of fresh meat and poultry. In R. T. Parry, Principles and applications of modi®ed atmosphere packaging of food (pp. 269±298). London: Blackie Academic and Professional. Ke, P. J., Ackman, R. G., Linke, B. H., & Nash, D. M. (1977). Differential lipid oxidation in various parts of frozen mackerel. Journal of Food Technology, 12, 37±47. Kerry, J. P., Burkley, E., O'Sullivan, M. G., Lynch, A., Buckley, D. J. & Morrissey, P. A. (1996). The eect of packaging on colour, oxidation and microbiological status of beef from vitamin E supplemented cattle. In Proceedings of the 42nd international congress of meat science and technology, (pp.94±95) 1±6 September, Lillehammer, Norway. Krzywicki, K. (1979). Assessment of relative content of myoglobin, oxymyoglobin and metmyoglobin at the surface of beef. Meat Science, 3, 1±10. Lanari, M. C., Schaefer, D. M., Cassens, R. G., & Scheller, K. K. (1995a). Atmosphere and blooming time aect color and lipid stability of frozen beef from steers supplemented with vitamin E. Meat Science, 40, 33±44.
66
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
Lanari, M. C., Schaefer, D. M., & Scheller, K. K. (1995b). Dietary vitamin E supplementation and discoloration of pork bone and muscle following modi®ed atmosphere packaging. Meat Science, 41, 237±250. Liu, Q., Lanari, M. C., & Schaefer, D. M. (1995). A review of dietary vitamin E supplementation for improvement of beef quality. Journal of Animal Science, 73, 3131±3140. Morrissey, P. A., Buckley, D. J., Sheehy, P. J. A., & Monahan, F. J. (1994). Vitamin E and meat quality. Proceedings of the Nutrition Society, 53, 289±295. Renerre, M. (1990). Factors involved in the discolouration of beef meat. International Journal of Food Science and Technology, 25, 613±616. Sheehy, P. J. A., Morrissey, P. A., & Flynn, A. (1993). In¯uence of heated vegetable oils and a-tocopheryl acetate supplementation on a-tocopherol, fatty acids and lipid peroxidation in chicken muscle. British Poultry Science, 34, 367±381.
Sherbeck, J. A., Wulf, D. M., Morgan, J. B., Tatum, J. D., Smith, G. C., & Williams, S. N. (1995). Dietary supplementation of vitamin E to feedlot cattle aects retail display properties. Journal of Food Science, 60, 250±252. Strohecker, M. G., Faustman, C., Furr, H., Hoagland, T. A., & Williams, S. N. (1997). Vitamin E supplementation eects on lipid and colour stability of whole and ground lamb. Journal of Muscle Foods, 8, 413±426. Taylor, A. A., Down, N. F., & Shaw, B. G. (1990). A comparison of modi®ed atmosphere and vacuum skin packing for the storage of red meats. International Journal of Food Science and Tecnology, 25, 98±109. Wulf, D. M., Morgan, J. B., Sanders, S. K., Tatum, J. D., Smith, G. C., & Williams, S. (1995). Eects of dietary supplementation of vitamin E on storage and caselife properties of lamb retail cuts. Journal of Animal Science, 75, 399±405.
www.elsevier.com/locate/meatsci
The eects of dietary a-tocopheryl acetate supplementation and modi®ed atmosphere packaging (MAP) on the quality of lamb patties J.P. Kerry a,*, M.G. O'Sullivan a, D.J. Buckley a, P.B. Lynch b, P.A. Morrissey a a
Department of Food Science and Technology, University College Cork Ð National University of Ireland, Cork, Ireland b Teagasc, Moorepark, Fermoy, Co. Cork, Ireland Received 3 July 1998; received in revised form 5 January 2000; accepted 26 January 2000
Abstract The eects of dietary a-tocopheryl acetate supplementation and/or packaging on the quality of lamb patties were investigated. Ewes (n=12) were selected and scanned to assess pregnancy. They were divided into two groups (n=6). The control group was fed a non-supplemented diet of 20 mg a-tocopheryl acetate/kg feed/day for 9 weeks ante-parturition and 3 weeks post-parturition. The lambs were weaned at 3 weeks and fed either the non-supplemented or supplemented diet for 10 weeks prior to slaughter. The M. longissimus dorsi from each carcass from each dietary group was stored at ÿ20 C for 7 months. Patties were formed from supplemented or control minced m. longissimus dorsi and held in either modi®ed atmosphere packs (MAP) under atmospheres of 70:30, 80:20 or 90:10 CO2:O2, under vacuum or in overwrapped trays. All packs were held under refrigerated (4 C, 616 lux) display for a period of 10 days. Patties were assessed for oxidative and colour stability on days 0, 2, 4, 6, 8 and 10. With each type of pack, dietary a-tocopheryl acetate supplementation signi®cantly increased oxidative and colour stability compared to control patties. As oxygen concentrations increased in MAP packs, colour stability was enhanced but the rate of lipid oxidation increased. Vacuum packaged patties had signi®cantly (P<0.05) higher Hunter `a' values, lower proportions of metmyoglobin and lower TBARS numbers than those held under all other forms of packaging. Aerobically packaged patties had lower Hunter `a' values, higher proportions of metmyoglobin and lower TBARS numbers compared to MAP patties. # 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction The three sensory properties by which consumers most readily judge meat quality are appearance, texture and ¯avour (Liu, Lanari & Schaefer, 1995). At the point of sale, colour and colour stability are the most important attributes of meat quality and various approaches have been used to meet consumer expectation that an attractive, bright-red colour indicates a long shelf-life and good eating quality (Hood & Mead, 1993). In red meats, consumers relate the bright red colour to freshness, while discriminating against meat which has turned brown in colour (Morrissey, Buckley, Sheehy & Monahan, 1994). The loss of the bright red colour is caused by the oxidation of the red oxymyoglobin to the * Corresponding author. Tel.: +353-21-902256; fax: +353-21276318. E-mail address: [email protected] (J.P. Kerry).
undesirable brown metmyoglobin (Faustman & Cassens, 1990). Discolouration in retail meats during display conditions may occur as a combined function of muscle pigment oxidation (oxymyoglobin to metmyoglobin) and lipid oxidation in membrane phospholipids (Sherbeck, Wolf, Morgan, Tatum, Smith & Williams, 1995). The rate of colour loss in fresh meat is dependent on the temperature of storage (Renerre, 1990). Low storage temperature combined with high oxygen tension or the exclusion of air are the preferred methods of preserving fresh meat colour (Gill, 1996). Modi®ed atmosphere packs (MAP) are becoming popular with retailers for packaging fresh meat cuts. The evolution of MAP for fresh meat has also occurred in response to the need for de®ned packaging environments related to the properties of meat from dierent species and the need to satisfy speci®c marketing requirements (Hood & Mead, 1993). It is now widely accepted that dietary supplementation with a-tocopheryl acetate eectively controls lipid
0309-1740/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(00)00021-8
62
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
oxidation and colour deterioration in red meats like lamb (Guidera, Kerry, Buckley, Lynch & Morrissey, 1997a,b) and beef (Sherbeck et al., 1995). While a number of studies have investigated the relationship between lamb quality and MAP (Doherty, Sheridan, Allen, McDowell & Blair, 1997) and the eects of dietary vitamin E supplementation on colour and oxidative stability in lamb (Guidera et al., 1997a,b; Strohecker, Faustman, Furr, Hoagland & Williams, 1997), only a limited number of studies have been reported on the eects of vitamin E supplementation and MAP on red meat quality (Formanek, Kerry, Buckley, Morrissey & Farkas, 1998; Kerry, Burkley, O'Sullivan, Lynch, Buckley & Morrissey, 1996; Lanari, Schaefer, Cassens & Scheller, 1995a; Lanari, Schaefer & Scheller, 1995b). The aim of this study was to examine the eects of dietary a-tocopheryl acetate supplementation, the use of MAP in relation to other forms of packaging and the eects of storage time, on a-tocopherol content, oxidative properties, colour and overall keeping quality of lamb patties, held under refrigerated (4 C) display. 2. Materials and methods 2.1. Chemicals All chemicals were of AnalaR grade and obtained from the British Drug House, Poole, Dorset, UK; Sigma Chemical Co. Ltd., Poole, Dorset, UK and Rathburn Chemical Co. Ltd., Walkerburn, Peableshire, Scotland, UK. a-Tocopheryl acetate was obtained from Roche Products Ltd., Welwyn, Garden City, Hertfordshire, UK. 2.2. Animals and diet Twelve CheviotBorder Leicester ewes, scanned to assess that they were pregnant with twins, were randomly assigned to two groups (n=6) which were fed diets containing 20 (non-supplemented) and 1000 (supplemented) mg a-tocopheryl acetate/kg feed/day for 9 weeks prior and 3 weeks post-parturition. Lambs remained on the same level of supplementation as their mothers throughout the experiment. Lambs were slaughtered 13 weeks post-parturition. The conditions of housing and diets of both ewes and lambs have been reported previously (Guidera et al., 1997a). 2.3. Sampling and analysis After slaughter and evisceration, the lamb carcasses were chilled overnight, then the m. longissimus dorsi was removed from each carcass, vacuum-packed and stored at ÿ20 C for 7 months. Frozen m. longissimus dorsi was thawed (4 C for 12 h) and minced using a MAINCA
rust-free steel meat mincer (MAINCA, C/Jaume Ferran s/n, Granollers, Barcelona, Spain) through a plate diameter of 5 mm into plastic bags. Patties (80 g) were formed from both supplemented and non-supplemented lamb meat prior to packaging. 2.4. Packaging and storage conditions Lamb patties were placed on polystyrene/EVOH/ polyethylene trays and overwrapped with oxygen permeable (6000±8000 cm3/m2/24 h at STP) polyvinylchloride ®lm (Wrap Film Systems Ltd., Shropshire, UK) for aerobic packaging, or heat-sealed within these trays to create headspace using a low oxygen permeable (8±12 cm3/m2/24 h at STP) polyester-EVOH-polyethylene ®lm (Boss Packaging Ltd., Bad Homburg, Germany) for MAP using packing machine type: VS 100 BS (Gustav MuÈller and Co., Zum Wingert 5, 6380 Bad Homburg 6, Germany). The gas mixtures used for MAP were 70:30, 80:20 or 90:10 oxygen:carbon dioxide. Patties were vacuum-packaged using a Webomatic type: D463 (Webomatic Vacuum Packaging Systems, Werner Bonk, Mausegatt 59, D 463 Bochum 6, Germany) vacuum packer. The vacuum packaging material consisted of Cryovac polyamide/polyethylene 20/70 low oxygen permeable multi¯ex ®lms (Cryovac, W.R. Grace Europe Inc., Av. Montchoisi 35, 1001 Lausanne, Switzerland) (45 cm3/m2/24 h at STP). Patties were displayed for up to 10 days at 4 C under ¯uorescent light (616 lux). 2.5. -Tocopherol determination The a-tocopherol contents of m. longissimus dorsi from supplemented or non-supplemented lamb were determined in lamb meat after slaughter, after thawing and mincing previously frozen (ÿ20 C for 7 months) primal cuts and from patties held under dierent packaging conditions. a-Tocopherol in minced lamb was extracted using the method of Sheehy, Morrissey and Flynn (1993) and quanti®ed by HPLC using a Waters model S10 pump, a Waters 717 autosampler, a Machery-Nagel Nucleosil 5 C18 (2500.4 mm) reverse phase column and a Waters model 486 UV±visible wavelength detector (Millipore Corporation, Milford, MA 01757, USA) set at 292 nm. The mobile phase was methanol:water (97:3) at a ¯ow rate of 2 ml/min. Data were recorded and evaluated using a Millipore Millenium 2010 chromatography management system (Millipore Corporation, Milford, MA 01757, USA). 2.6. Determination of lipid oxidation Lipid oxidation was assessed by the 2-thiobarbituric acid method (TBARS) (Ke, Ackman, Linke & Nash, 1977) and expressed as mg malonaldehyde/kg muscle.
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
63
2.7. Colour analysis
3.2. Colour stability of lamb patties
Hunter L, a, b values were determined using a Minolta Chromameter CR-300 (Minolta Camera Co., Osaka, Japan). Colour readings were measured by placing the calibrated hand held probe of the Minolta Chromameter in contact with the overwrapped patties. Metmyoglobin formation (Krzywicki, 1979) was also determined in these samples using a Perkin-Elmer (Lambda 2) spectrophotometer (Perkin-Elmer Corporation, Norwalk, CI, USA).
3.2.1. Hunter 'a' values The eects of dietary a-tocopheryl acetate supplementation on Hunter 'a' values of lamb patties for various packaging systems are shown in Fig. 1. Hunter 'L' and 'b' values showed no overall trends during storage. Higher Hunter 'a' values were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs from days 2 to 6 (P<0.01) and days 8 to 10 (P<0.05), aerobically on days 2 (P<0.01) and day 4 (P<0.05) and under vacuum on d 2 (P<0.05). Both supplemented and nonsupplemented lamb patties packaged under vacuum had higher Hunter 'a' values compared to all other packaging systems and these dierences were signi®cant on day 4 (P<0.05) and days 6 to 10 (P<0.01). Supplemented lamb patties packaged in MAP packs had signi®cantly (P<0.05) higher Hunter 'a' values than patties held in aerobic packaging from day 2 to 6. Nonsupplemented lamb patties held in aerobic packs had the lowest Hunter 'a' values of all meat samples on day 2 and 4. These values were signi®cantly lower than nonsupplemented patties held in MAP packs. However, on day 6, Hunter 'a' values for 90:10 O2:CO2 were signi®cantly (P < 0.05) lower than those for aerobically packaged or other MAP non-supplemented patties. By day 10, all non-supplemented patties held in MAP had signi®cantly (P<0.05) lower Hunter 'a' values than aerobically packaged or supplemented patties held
2.8. Statistical analysis Comparisons between dietary treatments for a-tocopherol levels were tested using Student's t-test. ANOVA repeated analysis of variance was performed on data obtained from the oxidative and colour analysis of patties using the statistical package SPSS (SPSS Ltd., West St, Woking, Surrey, UK). 3. Results and Discussion 3.1. -Tocopherol levels in lamb meat a-Tocopherol concentrations were higher (P<0.05) in supplemented (5.30.3 mg/g muscle) than non-supplemented (0.80.2 mg/g muscle) m. longissimus dorsi. A signi®cant (P<0.001) decrease from 5.30.3 to 2.90.1 mg a-tocopherol/g muscle was observed in minced supplemented m. longissimus dorsi after frozen storage at ÿ20 C for 7 months. These results are in agreement with those reported by Guidera et al. (1997a). The a-tocopherol levels in non-supplemented lamb meat held in vacuum packs, aerobically or in 70:30, 80:20 or 90:10 O2:CO2 MAP packs after 10 days were 0.60.1, 0.50.1, 0.10.0, 0.10.1 and 0.10.1 mg/g meat, respectively. a-Tocopherol levels present in supplemented m. longissimus dorsi patties held in vacuum packs, aerobically or in 70:30, 80:20 and 90:10 O2:CO2 MAP packs after 10 days were 2.90.1, 2.60.3, 1.50.2, 1.20.1 and 0.80.1 mg/g meat, respectively. The decreases in a-tocopherol levels in both supplemented and non-supplemented lamb meat held under MAP were signi®cant (P<0.05) in all cases. These results have not been presented for lamb previously but are in agreement with those reported by Formanek et al. (1998) for a-tocopheryl acetate supplemented beef held under MAP conditions. They reported that over time, greater reductions in minced beef atocopherol levels occurred as oxygen concentrations increased within packs. Formanek et al. (1998). suggested that as oxygen concentrations increased within packs, an increase in the oxygen reactive species also occurred, thereby consuming a-tocopherol.
Fig. 1. Eect of dietary a-tocopheryl acetate and packaging on Hunter 'a' values in lamb patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. Hunter 'a' values in lamb patties from the nonsupplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2, (~,~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
64
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
under MAP conditions. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a, 1997b), Strohecker et al. (1997) and Wulf, Morgan, Sanders, Tatum, Smith and Williams (1995). However, as indicated above, no information is available regarding the use of dietary atocopheryl acetate supplemented lamb in relation to colour stability in various packaging systems. Lanari et al. (1995a) did observe that MAP increased colour stability in frozen beef when compared to aerobically packaged samples. They also found that the colour stability of MAP frozen beef samples was signi®cantly enhanced by a-tocopheryl acetate supplementation. Similar results were also reported by Kerry et al. (1996) for fresh beef samples following a-tocopheryl acetate supplementation. Therefore, it would appear that overall colour trends reported for studies investigating the eects of a-tocopheryl acetate supplementation and packaging on beef quality are in agreement with the data presented here for lamb. 3.2.2. Metmyoglobin formation The eects of dietary a-tocopheryl acetate supplementation on metmyoglobin formation in lamb patties held in various packaging systems are shown in Fig. 2. Lower proportions of metmyoglobin were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs on days 2 and 4 (P<0.01) and days 6 (P<0.05), aerobically on
Fig. 2. Eect of dietary a-tocopheryl acetate and packaging on metmyoglobin formation in patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. Metmyoglobin formation in lamb patties from the non-supplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2, (~, ~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
days 2 and 4 (P<0.01) and day 6 (P<0.05). No signi®cant dierences were observed between supplemented and non-supplemented lamb patties held in vacuum packs. Both supplemented and non-supplemented lamb patties packaged under vacuum had lower proportions of metmyoglobin compared to all other packaging systems and these dierences were signi®cant on days 2 to 10 (P<0.01). Supplemented lamb patties packaged in MAP packs had signi®cantly (P<0.05) lower proportions of metmyoglobin than patties held in aerobic packaging from days 2 to 6. Non-supplemented lamb patties held in aerobic packs had the highest proportions of metmyoglobin of all meat samples on days 2 and 4. These values were signi®cantly (P<0.05) higher than non-supplemented patties held in MAP packs on day 2. On days 8 and 10, no signi®cant dierences were observed between supplemented or non-supplemented lamb patties held in aerobic or MAP conditions. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a,1997b), Strohecker et al. (1997) and Wulf et al. (1995). However, no information is available regarding the use of dietary a-tocopheryl acetate supplemented lamb in relation to metmyoglobin development in various packaging systems. In beef studies, Taylor, Down and Shaw (1990) and Gill and Jones (1994) found that a lower percentage of metmyoglobin was detected in vacuum-packed beef than in MAP packaged samples during storage. These ®ndings support those presented for lamb in this study. Kerry et al. (1996) found that metmyoglobin formation in beef steak cores packaged under MAP and air increased at the same rate over 10 days of refrigerated display. However, these authors also found that metmyoglobin formation was reduced in all packs, particularly MAP (80:20, O2:CO2), when atocopheryl acetate supplemented beef was assessed. The combination eect of a-tocopheryl acetate supplementation and packaging type was also observed for lamb in this study. 3.2.3. Oxidative stability of lipids in lamb patties The eect of dietary a-tocopheryl acetate supplementation on TBARS values in lamb patties held in various packaging systems are shown in Fig. 3. Lower TBARS values were found in supplemented lamb patties compared to non-supplemented patties following storage in MAP packs on days 2 to 10 (P<0.01), aerobically on days 2 to 10 (P<0.01) and under vacuum on days 8 and 10 (P<0.05). In general, both supplemented and non-supplemented lamb patties packaged under vacuum had lower TBARS values compared to other packaging systems. These dierences were signi®cant on days 2 to 10 for supplemented lamb patties and from days 4 to 8 (P<0.05) for non-supplemented lamb patties.
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
65
beef steaks and steak cores from cattle fed a control diet. However, this detrimental eect was oset or reduced by a-tocopheryl acetate supplementation. Similar to the results presented in this study, Formanek et al. (1998) reported that TBARS values in a-tocopheryl acetate supplemented minced beef were reduced in aerobic, vacuum and MAP packs compared to non-supplemented beef following refrigerated storage for 10 days. Similarly, these authors also showed that TBARS values increased in minced beef as oxygen levels increased in MAP packs and that vacuum packing was most eective in controlling the development of lipid oxidation. Acknowledgements Fig. 3. Eect of dietary a-tocopheryl acetate and packaging on the oxidative stability (TBARS) in lamb patties formed from previously frozen (ÿ20 C for 7 months) m. longissimus dorsi and held at 4 C under ¯uorescent light for up to 10 days. TBARS from lamb patties from the non-supplemented dietary group containing 20 mg a-tocopheryl acetate/kg feed (closed symbols) or for lamb patties from the dietary group supplemented with a-tocopheryl acetate (1000 mg/kg feed) (open symbols). (&,&) MAP 70:30, O2:CO2, (*,*) MAP 80:20, O2:CO2 (~,~) MAP 90:10, O2:CO2, (^,^) air and (!,!) vacuum packaging. Mean valuesS.E.M. for six analyses performed in duplicate.
Supplemented lamb patties packaged in 70:30, O2:CO2 and 80:20, O2:CO2 MAP had equivalent TBARS values to those of aerobically packaged samples. Supplemented lamb patties held in 90:10, O2:CO2 MAP had signi®cantly (P<0.05) higher TBARS values than either aerobically packaged or 70:30, O2:CO2 and 80:20, O2:CO2 MAP samples. Non-supplemented lamb patties held in aerobic packs had higher TBARS values compared to supplemented lamb patties held in 90:10, O2:CO2 MAP from days 6 to 10 (P<0.05) and 70:30, O2:CO2 and 80:20, O2:CO2 MAP from days 2 to 10 (P<0.05). The highest TBARS values were determined for non-supplemented lamb patties packaged in all three MAP atmospheres and these were signi®cantly (P<0.01) higher than levels determined for other packaging systems from days 4 to 10. Non-supplemented patties packaged in 90:10, O2:CO2 MAP had signi®cantly (P<0.05) higher TBARS values than patties held in either 70:30, O2:CO2 or 80:20, O2:CO2 MAP atmospheres. The data presented here for aerobic or overwrapped non-supplemented and supplemented lamb patties are in line with those presented by Guidera et al. (1997a,1997b), Strohecker et al. (1997) and Wulf et al. (1995). However, no information is available regarding the use of dietary a-tocopheryl acetate supplemented lamb in relation to oxidative stability in various packaging systems. However, similar results to those reported in this paper have been presented for beef. Kerry et al. (1996) found that MAP promoted lipid oxidation in
We would like to thank Homann-La Roche, Basel, Switzerland for the funding of this work. References Doherty, A. M., Sheridan, J. J., Allen, P., McDowell, D. A., & Blair, I. S. (1996). Physical characteristics of lamb primals packaged under vacuum or modi®ed atmospheres. Meat Science, 42, 315±324. Faustman, C., & Cassens, R. G. (1990). In¯uence of aerobic metmyoglobin reducing capacity on colour stability of beef. Journal of Food Science, 55, 1279±1283. Formanek, Z., Kerry, J. P., Buckley, D. J., Morrissey, P. A. & Farkas, J. (1998). Eects of dietary vitamin E supplementation and packaging on the quality of minced beef. Meat Science, 50, 203±210. Gill, C. O. (1996). Extending the storage life of raw chilled meats. Meat Science, 43, S99±S109. Gill, C. O., & Jones, T. (1994). The display of retail packs of ground beef after their storage in master packages under various atmospheres. Meat Science, 37, 281±295. Guidera, J., Kerry, J. P., Buckley, D. J., Lynch, P. B., & Morrissey, P. A. (1997a). The eect of dietary vitamin E supplementation on the quality of fresh and frozen lamb meat. Meat Science, 45, 33±43. Guidera, J., Kerry, J. P., Buckley, D. J., Lynch, P. B., & Morrissey, P. A. (1997b). The eect of dietary a-tocopheryl acetate supplementation on muscle a-tocopherol levels and lamb quality. Irish Journal of Agricultural and Food Research, 36, 241±247. Hood, D. E., & Mead, G. C. (1993). Modi®ed atmosphere storage of fresh meat and poultry. In R. T. Parry, Principles and applications of modi®ed atmosphere packaging of food (pp. 269±298). London: Blackie Academic and Professional. Ke, P. J., Ackman, R. G., Linke, B. H., & Nash, D. M. (1977). Differential lipid oxidation in various parts of frozen mackerel. Journal of Food Technology, 12, 37±47. Kerry, J. P., Burkley, E., O'Sullivan, M. G., Lynch, A., Buckley, D. J. & Morrissey, P. A. (1996). The eect of packaging on colour, oxidation and microbiological status of beef from vitamin E supplemented cattle. In Proceedings of the 42nd international congress of meat science and technology, (pp.94±95) 1±6 September, Lillehammer, Norway. Krzywicki, K. (1979). Assessment of relative content of myoglobin, oxymyoglobin and metmyoglobin at the surface of beef. Meat Science, 3, 1±10. Lanari, M. C., Schaefer, D. M., Cassens, R. G., & Scheller, K. K. (1995a). Atmosphere and blooming time aect color and lipid stability of frozen beef from steers supplemented with vitamin E. Meat Science, 40, 33±44.
66
J.P. Kerry et al. / Meat Science 56 (2000) 61±66
Lanari, M. C., Schaefer, D. M., & Scheller, K. K. (1995b). Dietary vitamin E supplementation and discoloration of pork bone and muscle following modi®ed atmosphere packaging. Meat Science, 41, 237±250. Liu, Q., Lanari, M. C., & Schaefer, D. M. (1995). A review of dietary vitamin E supplementation for improvement of beef quality. Journal of Animal Science, 73, 3131±3140. Morrissey, P. A., Buckley, D. J., Sheehy, P. J. A., & Monahan, F. J. (1994). Vitamin E and meat quality. Proceedings of the Nutrition Society, 53, 289±295. Renerre, M. (1990). Factors involved in the discolouration of beef meat. International Journal of Food Science and Technology, 25, 613±616. Sheehy, P. J. A., Morrissey, P. A., & Flynn, A. (1993). In¯uence of heated vegetable oils and a-tocopheryl acetate supplementation on a-tocopherol, fatty acids and lipid peroxidation in chicken muscle. British Poultry Science, 34, 367±381.
Sherbeck, J. A., Wulf, D. M., Morgan, J. B., Tatum, J. D., Smith, G. C., & Williams, S. N. (1995). Dietary supplementation of vitamin E to feedlot cattle aects retail display properties. Journal of Food Science, 60, 250±252. Strohecker, M. G., Faustman, C., Furr, H., Hoagland, T. A., & Williams, S. N. (1997). Vitamin E supplementation eects on lipid and colour stability of whole and ground lamb. Journal of Muscle Foods, 8, 413±426. Taylor, A. A., Down, N. F., & Shaw, B. G. (1990). A comparison of modi®ed atmosphere and vacuum skin packing for the storage of red meats. International Journal of Food Science and Tecnology, 25, 98±109. Wulf, D. M., Morgan, J. B., Sanders, S. K., Tatum, J. D., Smith, G. C., & Williams, S. (1995). Eects of dietary supplementation of vitamin E on storage and caselife properties of lamb retail cuts. Journal of Animal Science, 75, 399±405.