kg) of α-TA.3. Feed and water were provided ad libitum. Egg produc- tion was recorded daily. The egg quality was measured three times during the experiment, ...
α-Tocopherol Transfer Efficiency and Lipid Oxidation in Fresh and Spray-Dried Eggs Enriched with ω3-Polyunsaturated Fatty Acids J. Galobart,† A. C. Barroeta,†1 M. D. Baucells,† L. Cortinas,† and F. Guardiola‡ †Departament de Cie`ncia Animal i dels Aliments, Facultat de Veterina`ria, Universitat Auto`noma de Barcelona, E-08193 Bellaterra, Spain; and ‡Departament de Nutricio´ i Bromatologia-CeRTA, Facultat de Farma`cia, Universitat de Barcelona, Avinguda Joan XXIII, E-08028 Barcelona, Spain ABSTRACT We evaluated the effect of supplementing a basal diet containing 5% linseed oil with 0, 50, 100, and 200 mg/kg of α-tocopheryl acetate (α-TA) on α-tocopherol content, fatty acid composition, and lipid oxidation in fresh and spray-dried eggs during storage. α-Tocopherol transfer efficiency from feed to egg was also studied. The α-tocopherol content of fresh egg increased in a dosedependent manner (16.6, 49.8, 78.9, and 132.3 µg/g of egg for 0, 50, 100, and 200 mg/kg α-TA supplementation,
respectively), but transfer efficiency decreased, from 41.8% to 26.7%, with increasing α-tocopherol content in the diet. Spray-drying significantly decreased the α-tocopherol content of eggs and increased lipid oxidation. Dietary supplementation with different levels of α-TA significantly reduced lipid oxidation in spray-dried eggs. α-TA supplementation had no significant effect on the fatty acid composition of fresh eggs.
(Key words: ω3-fatty acid enriched egg, dietary α-tocopherol supplementation, lipid oxidation, spray-dried egg, α-tocopherol transfer efficiency) 2001 Poultry Science 80:1496–1505
INTRODUCTION Because of the health benefits associated with ω3-fatty acids (FA), much research in recent years has focused on enrichment of different foods of animal origin, especially broiler meat and eggs (Van Elswyk et al., 1992; Ajuyah et al., 1993; Cherian et al., 1996a,b; Lo´pez-Ferrer et al., 1999; Baucells et al., 2000). Higher polyunsaturated FA (PUFA) contents of these foods lead to increased unsaturation and, thus, to a major susceptibility to lipid oxidation. In the case of eggs, although lipids are not easily oxidized in shell fresh eggs (Pike and Peng, 1985), even during storage (Marshall et al., 1994; Cherian et al., 1996a), oxidation is facilitated when eggs are processed, especially when high temperature treatments are involved (e.g., cooking, spray-drying, etc.). Spray-dried eggs are widely used in the food industry (bakery products, cake mixes, sauces). Therefore, the control of lipid oxidation in such products is required to prevent loss of nutritional and organoleptic values as well as to prevent the forma-
2001 Poultry Science Association, Inc. Received for publication December 14, 2000. Accepted for publication May 26, 2001. 1 To whom correspondence should be addressed: Ana.Barroeta@ uab.es.
tion of potentially toxic compounds (Kubow, 1990; Chow, 1992). To this end, antioxidants are often used in the food industry. Synthetic antioxidants (e.g., butylated hydroxytoluene, butylated hydroxyanisole) have been progressively replaced by natural antioxodants (Qi and Sim, 1998). Tocopherols are a reliable choice and have been tested successfully in several food products. Supplementation of animal diets with tocopherols increases the content of this natural antioxidant in animal food products and prevents lipid oxidation in broiler meat (Ajuyah et al., 1993), turkey meat (Ahn et al., 1998), pork (Kingston et al., 1998), rabbit meat (Lo´pez-Bote et al., 1997), and eggs and egg products (Wahle et al., 1993; Cherian et al., 1996a; Qi and Sim, 1998; Galobart et al., 1999, 2001). However, previous research used high dietary doses of this natural antioxidant, and there is not sufficient data regarding the effect of graded levels of α-tocopherol on the composition and lipid oxidation of fresh and spraydried eggs enriched with ω3-FA or the evolution of these parameters during storage. Moreover, the transfer efficiency of α-tocopherol from feed to egg has not been studied in depth (Naber, 1993; Grobas, 1997).
Abbreviation Key: CHP = cumene hydroperoxide; FA = fatty acid; LDL = low density lipoproteins; LHP = lipid hydroperoxides; LNA = linolenic acid; MDA = malondialdehyde; PUFA = polyunsaturated fatty acids; α-TA = α-tocopheryl acetate.
1496
1497
α-TOCOPHEROL TRANSFER EFFICIENCY AND LIPID OXIDATION IN EGGS
The objective of the present study was to determine the effect of dietary supplementation with different levels of α-tocopheryl acetate (α-TA) on FA composition, the α-tocopherol transfer efficiency from feed to egg, and the effect of this antioxidant, the spray-drying process, and storage on α-tocopherol content and lipid oxidation in eggs enriched with ω3-FA.
MATERIALS AND METHODS Animals and Diets The experiment received prior approval from the Animal Protocol Review Committee of the Universitat Auto`noma de Barcelona. All animal housing and husbandry conformed to the European Union guidelines. One hundred forty-four Lohman laying hens were randomly distributed into four dietary treatments. Six replicates of six hens per dietary treatment were carried out. Diets were formulated to meet or exceed NRC (1994) requirements (Table 1). Experimental treatments resulted from the supplementation of a basal diet containing 5% linseed oil2 with one of four levels (0, 50, 100, or 200 mg/ kg) of α-TA.3 Feed and water were provided ad libitum. Egg production was recorded daily. The egg quality was measured three times during the experiment, including Haugh units, shell thickness, and yolk color (measured by the Roche Color Fan score and by means of using a HunterLab4 colorimeter and expressed using the Lab scale). Feed consumption was measured throughout the experiment. Feed was sampled three times for FA and α-tocopherol analyses.
Sample Collection After 25 d of feeding, all eggs produced were collected during 4 d and were kept at 4 C. Five eggs per replicate of each treatment were then cracked, homogenized, and frozen at −80 C until the analyses [FA composition, αtocopherol content, and lipid hydroperoxide (LHP) and TBA values]. The rest of the eggs were also cracked, homogenized, and stored at −20 C until the spray-drying process, which was performed by means of a cyclonetype spray-dryer,5 with inlet and outlet temperatures of 160 and 90 C, respectively. Spray-dried eggs were stored in closed glass containers at room temperature in the dark, and α-tocopherol content, LHP and TBA values were determined after 0, 2, 4, and 6 mo of storage.
2 Linseed oil was provided by Caila´-Pare´s, S.A., E-08040 Barcelona, Spain. 3 Rovimix威 E-50 Adsorbate, F. Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland. 4 HunterLab, Reston, VA 20190-5280. 5 Spray-dryer SD-05威, Lab-Plant Ltd., HD3 4EL Huddersfield, England. 6 Shimadzu Corporation, 604-8511 Kyoto, Japan. 7 SGE, 3134 Ringwood, Victoria, Australia. 8 Shimadzu Europe GmbH, D-47269 Duisburg, Germany.
TABLE 1. Composition of the basal diet Ingredient Corn Soybean meal (44% CP) Barley Wheat Linseed oil Calcium carbonate Dicalcium phosphate DL-Methionine Salt Vitamin and mineral premix1 Composition ME, kcal/kg2 DM CP Crude fiber Crude fat Ash Calcium2 Phosphorus2 Lys2 Met2 Met + Cys2
% 38.80 24.04 10.53 10.00 5.00 8.57 2.12 0.14 0.40 0.40 100.00 2,893.00 91.52 15.76 3.10 7.12 14.20 3.82 0.45 0.83 0.38 0.69
1 Supplied per kilogram of total diet: vitamin A: 8,000 IU; cholecalciferol: 1,600 IU; vitamin K3: 2 mg; vitamin B1: 1.5 mg; vitamin B2: 4 mg; vitamin B6: 3 mg; vitamin B12: 11.8 µg folic acid: 0.35 mg; biotin: 150 µg; pantothenic acid: 10 mg; nicotinic acid: 20 mg; Mn: 30 mg; Zn: 50 mg; I: 0.3 mg; Fe: 50 mg; Cu: 6 mg; Se: 0.1 mg. 2 Calculated value. Assayed concentrations of α-tocopherol for the different diets were
