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Studies of Consumer Acceptance of High Omega-3 Fatty Acid-Enriched Eggs
01997AppliedPoullry Sdcncc Inc
STUDIES OF CONSUMER ACCEPTANCE OF HIGHOMEGA-3 FATTY ACID-ENRICHED EGGS
Primary Audience: Egg Producers and Processors, Nutritionists, Food Scientists
DESCRIPTION OF PROBLEM The designer egg has received much attention as a potential source of "good" 52-3 fatty acids [l].The nutritional content of the egg yolk, i.e., fatty acid profile and vitamin E content, canbeefficientlyalteredbydietaryfat 1 To whom correspondence should be addressed
sources [2]. Common sources of 52-3 fatty acids in poultry diets, such as fish oil or flaxseed, have been shown to have a linear effect on 52-3fatty acid composition in the egg yolk as level of flaxseed or fish oil increases in the ration [3,4,51. A consumer survey indicates public interest in 52-3fatty acid-enriched eggs
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s.E. SCHEIDELXR~ Department ofAnimal Science, Universityof Nebmka, C2Mj Animal Science, Lincoln, NE 68583-0908 Phone: (402) 472-6451 F a : (402)472-6362 G. FRONING and S. CUPPE'IT Department of Food Science and Technology, Universityof Nebraska, Lincoln, NE 68583-090
138
ated by measuring the level of TBARS and color changes in egg yolks and by measuring changes in sensory attributes (appearance, texture, and flavor) in scrambled eggs produced from the eggs.
MA~RIALS AND METHODS TRIAL1 Eight diets (control, 1.5% dietary menhaden fish oil, and 5, 10, or 15% whole or ground golden flaxseed) were fed to four replicate pens with three DeKalb Delta 43-wkold laying hens per pen. Table 1 shows diet compositions, which were formulated to be isocaloric and equal in protein. Experimental diets were mixed once at the start of the study, stored at 21"C, and fed for 8 wk. Samples of eggs were collected from each treatment group after 6 wk. The eggs were analyzed for stability of yolk fatty acids and for sensory characteristics. TRIAL2 A 2 x 2 x 2 x 2 factorial arrangement of 16 dietary treatments was used to test the effects of a brown (Neche) vs. a golden (Omega) variety of flaxseed, ground vs. whole flaxseed, feed storage temperature (4 vs. 21"C), and two levels (27 vs. 50 IU) vitamin E supplementation on egg stability. Basal diets, like the diet shown in Table 1,included 10% flaxseed. Each diet was fed to four replicate pens with five 24-wk-old Babcock B300 laying hens per pen. Diets were fed for 6 wk, and eggs were collected for stability and sensory analysis at week 6. STABILITY AND COLOR ANALYSIS All eggs were candled and graded according to USDA standards, then refrigerated (12OC) for the duration of the study. To simulate commercial handling of eggs, test eggs were held in commercial egg cartons in a walk-in refrigerator. Stability was determined chemically by analyzing the egg yolk for levels of thiobarbituric acid reactive substances (TBARS) [14], using two duplicate samples per yolk. Results are expressed as mg TBARS/kg yolk. In 'Itial 1, five eggs per treatment were analyzed for TBARS after 2, 4, and 6 wk of refrigerated storage. In 'Rial 2, two replicates of two eggs per treatment were analyzed for TBARS at time 0 and after 8 wk of refrigerated storage.
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as dietary alternatives to fsh [6]. As demand and production of these enriched eggs increases, research is needed to determine their stability and consumer acceptability during storage. The stability of foods during storage is indicated by the level of oxidation products, such as thiobarbituricacid reactive substances (TBARS). TBARS reflect the amount of oxidation that the constituent fatty acids have undergone [6]. During lipid oxidation unsaturated fatty acids oxidize, producing hydroperoxides capable of reacting with thiobarbituric acid to produce a colored (pink) complex which can be measured spectrophotometrically. Pike and Peng [7J reported no change in egg yolk TBARS during cold storage that lasted for as long as 12 to 18 months. They postulated that egg yolk has an unusual stability in terms of lipid oxidation. However, the eggs they tested were not enriched with 53-3 fatty acids, which could have less stability due to the increased levels of unsaturation. Recent investigations by Aymond and Van Elswyk [8] reported no changes in egg yolk TBARS in eggs from hens fed flaxseed. Yolk color can also be directly affected by dietary ingredients, particularly by the dietary xanthophyll content. Flaxseed varieties have potential to affect yolk color due to their varied levels and types of xanthophylls [9]. Several investigators [lo, 11,12, U]have shown that alteration of the Q-3 fatty acid content in egg yolk can affect the eating (sensory) quality of the egg. Koehler and Bearse [9] first reported lower flavor ratings for eggs produced from hens fed 5% fish meal, as well as a very slight off-flavor in eggs from hens on a 6% menhaden oil diet. More recently investigators [12] reported a difference in sensory evaluation of scrambled eggs vs. hard-cooked a-3fatty acid-enriched eggs; panelists could more readily distinguish the regular scrambled eggs from the hard-cooked Q-3-enrichedeggs. All of these sensory evaluations of GI-3 fatty acid-enriched eggs were conducted on relatively fresh eggs. Our studies sought to investigate the effects of dietary menhaden oil, flaxseed level, dietary flaxseed variety, flaxseed preparation (ground vs. whole), feed storage temperature, and level of dietary vitamin E on the stability of fresh and stored eggs. Stability was evalu-
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELERel al.
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TABLE 1. Dietary composition and nutrient analysis
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*Menhaden fish oil was provided by Zapata Protein, Inc., Menhaden Oil Refinery, P.O. Box 175, Reedville, VA and was stabilized with W p p m ethoxyquin. %itamin E premix prmided an additional 50 W/kg vitamin E. %tamin/Mineral remix provided Mn,,88 mg; Cu, 6.6 m%;Fe, 8 5 mg; Zn,88 mg; Se,.O.? m ;vitamin A, 6,600IU; vitamin Dk 2,805 18;vttamin E, 10 IU; vltamm K,2.0 mg; nboflavin,4.4mg; pantothenicaad, 8.6 mg; niacin, 24.2 mg; choline, 110 mg,vitamin B1h 8.8 mg; ethoxyquin, 1.1 mg/kg.
140 Yolk color [15] was determined for eggs in Trial 2 only. Yolks from six eggs were separated from the whites and dried on a paper towel; two randomly selected yolks were then combined, giving three replications per treatment diet.
%all samples were prepared and evaluated on fresh eggs and eggs d e r 6 wk of refrigerated storage.In 'Itial2samples were evaluated on fresh eggs and eggs after 8 wk of refrigerated storage. A randomized complete block design was used for the sensory evaluations with blocking for panelists [18,19].
RESULTS AND DISCUSSION TRIAL 1 Dietary treatment effects on egg yolk fatty acid composition as reported by Scheideler and Froning [3] showed significant linear effects of dietary level of flaxseed on egg yolk 52-3fatty acid content. Diet significantly (P < .05) affected the level of oxidation (Table Z), as measured by TBARS, occurring in the eggs at all storage times (2,4, and 6 wk). Generally throughout the study eggs from the control diet had consistently lower TBARS values than the eggs from hens on the fish oil or flaxseed diets. Interestingly,the TBARS levels decreased (P< .01) over the 6 wk of storage. The reason for this time effect needs additional study, it may indicate the loss of active carbonyls due to reactions with other chemical components such as proteins, or antioxidant reactions occurring during storage. Eggs are very resistant to oxidative reactions due to natural antioxidant components, including egg yolk, vitamin E, avidin, and phosphatine [I. Within each test period, the effect of the flaxseed relative to the control was an increase in TBARS, especially at weeks where there seemed to be a linear increase in TBAFW associated with increasing percentage of flaxseed. The decrease in TBARS over time was consistent across all dietary treatment groups. Other researchers [SI have reported no significant treatment effect of flaxseed form (whole vs. ground) on egg yolk TBARS or of fish oil [6] on TBARS in eggs from hens fed 1.5% menhaden fish oil and stored for 0,2, or 4 wk. Results of seed preparation in this study are inconsistent, showing moderate effects of ground versus whole flaxseed on TBARS at 2 wk of storage only. When the eggs were evaluatedfor sensory attributes (Table 3) at time 0, results showed that eggs from hens fed the ground flaxseed, both 10 and 15% levels, were less (P< .OS) acceptable in appearance than the other treatment eggs. At 6 wk, eggs from the 10
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SENSORY EVALUATION Sensory evaluation utilized a descriptive scale for determining treatment effects on egg qualitylstability. All scales were 15 cm long; the scale rated the appearance, texture, and flavor, using 0 = very undesirable and 15 = very desirable. Off-flavor was measured where 0 = lacking and 15 = intense. Flavor was defined as typical "egg flavor;" the panelists defined off-flavor as any flavor other than egg. Overall acceptability was also included as a means of determiningthe potential "consumer" perception of the eggs, rated from 0 = very undesirable to 15 = very desirable. The nine panelists were recruited from graduate students at the Department of Food Science and Technology and the Department of Animal Science (University of NebraskaLincoln) [16]. To prepare the samples, three eggs per treatment were blended with 36 g whole milk for 30 sec using a hand blender. The blended egg mixture was poured into a heated (120°C) equilibrated (30 sec) teflon-lined electric skillet lightly coated with Pam cooking spray. Samples were cooked for 4 min with continuous mixing. After cooking, 10-g subsamples were placed into lidded plastic cups labelled with 3-digit codes. Samples remained in the refrigerator until all samples had been prepared and cooled to the same temperature, then reheated for 10 sec in a microwave. Preliminary work (data not shown) showed that this handling procedure did not af€ect sample evaluation. We established this procedure in order to prepare and serve the required number of sampleswhile assuring uniform product quality. Sample sets of four were served one sample at a time in a completeblock design so that each panelist tasted all samples. Treatments were replicated three times. All evaluations were performed in a controlled environment with panelists seated in individual lighted partitioned booths [17]. Panelists used room temperature water and unsalted-top crackers to clear their palates between samples. In
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELER et ai.
141
TBAR (m&
DIETARY TREATMENT
2 Wk
yolk)
4 Wk
6 Wk
Control
0.371'
0.29F
0.176'
0.473"
0.333'"
0.229
0.643'
0.29F
0.191''
5% Ground flaxseed
0.422'
0.268"
0.202d'c
10% Whole flaxseed 10%Ground flaxseed 15% Whole flaxseed
0.368'
0.326'*
0.224c3
0.432"
0.339'b
0.280ab
054Pb
0.366'
0.255"
15% Ground flaxseed
0.395'
0.362'b
0.295'
SEM
0.017
0.009
0.005
% Probability
df Diet effect
7
0.01
0.02
0.01
Time effect
2
0.01
0.01
0.01
DImARY TREATMENT
APPEARANCE* TEXTUREA
OWk I 6 W k
I Fishoil control I 5% Whole flaxseed I S%Groundflaxseed I lO%Wholeflaxseed I 10% Ground flaxseed I 15%Wholeflaxseed I Control
15% Ground flaxseed
9.03' 8.74' 8.69. 9.09" 85a"
7.41b 851' 7.16b
I 9.03a I 8.92' I 8.3Pb I 9.10' I 7MbC I 8.84' I 6.73"
8.40
8.61
8.76'
7.50
1
8.98
8.13 8.18 9.12 8.79
0.49
I I
I I
1
7.75 8.07
FLAVORA
I OWk
I6Wk
I 8.49a 1
858
OFF-
OVERALL ACCEPTABILITY/
FLAVOR^
I OWk
I6Wk
4.18
4.24
I
I 8.05' I 8.54 1
4.72
I
I I
451
I I
1
OWk 8.63 8.06
I
I
1
6Wk 8.478 8.3?
8.20
7.65
1 7.84' I 1 8.naI I 7.fl I
8.60
6LWb
8.60
5.61
4.36
6.92
8.7?
7.29
7.8?
7.23
4.88
6.37
7.79
7.13b
7.00
8.34
7.62 0.49
1
7Xb
0.42
I
7.30 8.36
8.47 0.42
I I I
5.95 455 4.79
I I
5.11
I
0.64
I
NS
I
454 5.11 5.08
5.19
I I I
7.69 8.41 7.72
7.42
0.64
I
0.43
NS
I
NS
I I I
7.95' 8.63' 8.32'
8.55'
I
0.43
I
0.05
Probabilitv
NS
Diet effect Timeeffect
I
I
NS
I
I 0.05
NS
I
0.05
I NS
NS
I 0.05
NS
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Fish oil control 5% Whole flaxseed
142
TRIAL 2 Table 4 shows dietary effects on TBARS production in eggs from Trial 2. There were no significant main effects of dietary treatment on TBARS at 0 or 8 wk of storage. There was a significant reduction in TBARS from 0 to 8 wk. This is similar to the effect of time on the reduction of TBARS found in W a l l . Although the decrease in TBARS was significant, it should be emphasized that all of the TBARS (0-and 8-wk storages) are relatively low. There was a significant interaction effect between variety of flaxseed fed and level of vitamin E supplemented, such that response to vitamin E supplementation varied according to variety of flaxseed. Vitamin E supplementation (50 IU/kg) lowered the TBARS at 0 wk in the golden variety and at 8 wk in the brown variety. The time effect of lowered TBARS between 0 and 8 wk was consistent between varieties and level of vitamin E fed.
SENSORY EVALUATION Table 5 shows the results of the sensory analysis of fresh eggs for 'Rial 2. Since there was no significant effect of storage time or interaction of time and diet effects in this trial, the second set of data (8 wk) are not given. Dietary effects on sensory evaluationin Trial 2 are limited to two treatment effects: variety on appearance and type of flaxseed preparation on texture. Eggs from hens fed the golden (Omega) variety of flaxseed had a higher ranking for appearance than the brown (Neche) variety of flaxseed, perhaps because of a different pigment composition in the two flaxseed varieties. 'Qpe of flaxseed preparation (whole vs. ground) had a significant effect on texture, with eggs from the whole flaxseed having a higher score than those from ground flaxseed. This observation of dietary flaxseed preparation effect on egg texture was not made in Trial 1's sensory analysis. Overall acceptability was not significantly affected by any of the dietary variables tested, but it should be noted that Trial 2 variables included only dietary flaxseed variety, preparation, storage temperature, and added vitamin E dietary flaxseed content remained constant at 10%. Table 6 shows the effects of Trial 2's dietary treatments on egg yolk color. Degree of lIghtness/darkness was significantly affected by variety of flaxseed (P < .01). The golden variety (Omega) of flaxseed produced a measurably lighter yolk than the brown (Neche) variety. This supports the appearance data in the sensory analysis study, similarly giving a higher ranking to eggs from the golden variety of flaxseed diets. Although not tested for, it appears that various varieties of flaxseed have different types of soluble pigments capable of incorporation into the egg yolk.
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and 15% whole flaxseed treatments had the least (P < .OS) acceptable appearance. Texture was not significantly different among treatments either at time 0 or at 6 wk. Flavor, i.e., "egg flavor," of the eggs from hens fed the ground flaxseed (10 and 15%) were less (P < .05) acceptable at time 0, but the effect did not occur at week 6. Off-flavor, i.e., flavor other than egg, was not affected by treatment at either 0 or 6 wk. Although there were differences in the acceptability of the eggs at time 0, these were not significant. However, at week 6 the eggs from the 15% whole flaxseed treatment were significantly (P < .05) less acceptable. Based on the data, fish oil and 5% levels of flaxseed did not affect the sensory acceptability of eggs; however, as the level of flaxseed increased, the eggs became less acceptable.
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELER et al.
143
TABLE 4. Thiobarbituric acid reactive substances (TBARS) for eggs at 0 and 8 wk of storage time (Flaxseed, Trial 2)
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JAPR OMEGA EGG ACCEPTANCE
144
8.99
8.05
8.45
4.29
7.97
8.65
8.11
8.28
4.51
7.69
(P value)
0.01
NS
NS
NS
NS
Whole
8.76
8.32
8.28
4.28
7.78
Ground
8.85
7.85
8.45
453
7.88
(P value)
NS
0.05
NS
NS
NS
4.4"C
8.83
7.98
8.37
452
7.84
21.0"
8.81
8.18
8.35
4.29
7.82
(P value)
NS
NS
NS
NS
NS
27 IU&
8.94
8.13
8.36
4.22
7.78
50 IUjkg
8.70
8.04
8.37
459
7.88
(P value)
NS
NS
NS
NS
NS
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Golden Bl-OWIl
Research Report 145
SCHEJDELER et al.
Whole
4.4
50
525
(-)3.00
31.9
Golden
Whole
21.0
50
535
(-)255
32.3
Golden
Ground
4.4
50
53.1
(-)2.66
32.2
Golden
Ground
21.0
50
54.4
(-)253
32.4
SEM
0.42
0.15
0.20
Golden
53.6
(-)2.73
32.40
BlDWl (P value)
52.4
(-)2.78
32.11
NS
NS
0.01
Whole
52.9
(-)2.90
32.2
Ground
53.2
(-)2.61
32.3
(P value)
NS
0.05
NS
4.4"c
52.7
(-)2.81
32.2
21.0"c (P value)
53.4 NS
(-)2.70 NS
32.3 NS
27 IUkg
53.0
(-)2.88
32.3
50 IU/kg
53.1
(-)2.63
32.2
(P value)
NS
NS
NS
CONCLUSIONS AND APPLICATIONS 1. Omega-3 fatty acid-enriched eggs from hens fed 1.5% menhaden fish oil or 5% flaxseed have minimal effects on consumer acceptance compared to non-enriched eggs; dietary levels of 10or 15%flaxseed, however, have somenegative effectson appearance and flavor.
2. Oxidative products in stored eggs as measured by TBARS decrease during refrigerated storage up to 8 wk, but did increase in eggs from flax-fed hens. 3. Variety of flaxseed (golden vs. brown) can affect egg yolk appearance and consumer perception of scrambled eggs.
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Golden
JAPR OMEGA EGG ACCEPTANCE
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REFERENCES AND NOTES 1. Van Elswyk, M.E, 1993. Designer Foods:Manipulatin the fatty acid composition of meat and e the f e a l t h conscious consumer. Nutrition E d 5 MarcWApril, pp. 21-27.
14. T.rlsdgis, B.G.,A.M.Pearson, and LR Dugan, Jr., 1964. Chemistry of the 2-thiobarbituric acid test for determination of oxidative rancidity in foods. J. Sci. Food Agnc. fi602-607.
2. Hargis P.S. and M.E Van ElsnyL, 1993. Manipulating the fatty acid composition of poult and meat and e g p for the health-conscious consumer. %orld’s Poultry Scl. 49251-264.
15.Yolks were blended for 30 sec then transferred to
5. Jiang, Z, D.U. Ahn, and J.S. Sim, 1991. Effect of feeding flaxseed and two of sunflower seed on fatty acid com osition of y o E p i d classes. Poultry Sci. 70:2457-2!75.
6. Mayshall, AC.,.A.R Sams, and M.E Van Ekwyk, 1994.Omdatrve stabilityand senso uality of stored e from hens fed 15% menhaden Food Sci. 5 9 5 e 563. 7. Pike,O.A. and1.C. Peng,1985.Stabili of shell e and liquid yolk to lipid oxidation. Poultry&. 64:14# 1475. 8. Aymond, W.M. and M.E Van m k , 1995. Yolk thiobarbituric acid reactive substances and 51-3 fattvacids nse to whole and ground flaxseed. Poultry Sci. kFx1394.
OX!.
having an L value of 95.47; and aL value of 0.61; and a b value of 0.40. L is lightneddarkness; a is a measure enness ) to redness (+); and b is a measure of $ l E e s s (+$ to blueness (-). 16. Panelists were familiarized with the rating form and scrambled egg samples in two 2-hr sessions nor to beginning the study. Trainin4 sam les were ma& using fresh commercial e g p obtained from a local grocery store. During training/familiarization panelists were seated at round tables and provided with necessary utensils, pencils, water, and unsalted-top crackers. Panelists were given three samples of scrambled e one at a time, in a randomized order. Panelists were a E 4 e d to work at their ownpaceandwere asked toevaluate t h e e p ymples using the provided form. After traininglfami ianzation, panelistsparticipated in a generaldiscussionto determine whether they had any problems using the forms to evaluate samples. 17.American Society for Testing and Materials, 1973. Standard Recommended Practices for Establishing Conditions for Laboratory Senso Evaluation of Foods and Averages. Committee E-18, $80. ASlX4, Philadelphia, PA.
9. Mayo, P . 5 , AR Spms, andM.E VmELFWyL, 1995. Yolk pigmentation in re me to dietary flaxseed seed. Poultry sci. 73(SuPpl):14Y 10. Kochler, H.H. and G.E Beprse, 1975. Epg flavor quality as affected by fish meals or fish oils in laying rations. Poultry Sci. Sk881-889. 11. A~OIUS,R L , D.L Pmtt, J.H. Lsn,andWJ. Stndelman, 1989. Introduction of omega-3 nsaturated fatty acids into eggs. Poultry sci. 68:166
g$.
12. Van Elswyk, M.E, AR Sams, and P.S. Har& 1992. Composition, functionality, and sensory evaluation from hens fed dietary menhaden oil. J. Food Sci.
19. SAS Imlitute, 1989. SASWAT User’s Guide. Version 6.4th Edition. Vol. 2. SAS Institute, Inc., Cary, NC.
ACKNOWLEDGEMENTS The authors would like to thank Lyle Robeson,
Lynn Niemann, and Minnie Stephens for their technical 13.Jiang,Af D.U.Anh,LLsdner,andJ.S. Sim, 1992. Influence of feeding full-fat flaxseed and sunflower seeds on internal and sensory qualities of e m . Poultry Sci. 71:378-382.
support in preparing this article. Financial sup ort of the North Dakota Oilseed Council is gratefup acknowledged.
Downloaded from http://japr.oxfordjournals.org/ at Georgetown University on May 23, 2015
3. Scheideler, LE and G.W. Froninp, 1996. The combined influence of dietary flaxseed variety, level, form, and storage conditions on egg roduction and composition among vitamin E. Poultry%. 75:1221-1226. 4. Caston, L and S. Letson, 1990. Research note: Dieta flaxseed and egg composition. Poultry Sci. 691617-1620.
STUDIES OF CONSUMER ACCEPTANCE OF HIGHOMEGA-3 FATTY ACID-ENRICHED EGGS
Primary Audience: Egg Producers and Processors, Nutritionists, Food Scientists
DESCRIPTION OF PROBLEM The designer egg has received much attention as a potential source of "good" 52-3 fatty acids [l].The nutritional content of the egg yolk, i.e., fatty acid profile and vitamin E content, canbeefficientlyalteredbydietaryfat 1 To whom correspondence should be addressed
sources [2]. Common sources of 52-3 fatty acids in poultry diets, such as fish oil or flaxseed, have been shown to have a linear effect on 52-3fatty acid composition in the egg yolk as level of flaxseed or fish oil increases in the ration [3,4,51. A consumer survey indicates public interest in 52-3fatty acid-enriched eggs
Downloaded from http://japr.oxfordjournals.org/ at Georgetown University on May 23, 2015
s.E. SCHEIDELXR~ Department ofAnimal Science, Universityof Nebmka, C2Mj Animal Science, Lincoln, NE 68583-0908 Phone: (402) 472-6451 F a : (402)472-6362 G. FRONING and S. CUPPE'IT Department of Food Science and Technology, Universityof Nebraska, Lincoln, NE 68583-090
138
ated by measuring the level of TBARS and color changes in egg yolks and by measuring changes in sensory attributes (appearance, texture, and flavor) in scrambled eggs produced from the eggs.
MA~RIALS AND METHODS TRIAL1 Eight diets (control, 1.5% dietary menhaden fish oil, and 5, 10, or 15% whole or ground golden flaxseed) were fed to four replicate pens with three DeKalb Delta 43-wkold laying hens per pen. Table 1 shows diet compositions, which were formulated to be isocaloric and equal in protein. Experimental diets were mixed once at the start of the study, stored at 21"C, and fed for 8 wk. Samples of eggs were collected from each treatment group after 6 wk. The eggs were analyzed for stability of yolk fatty acids and for sensory characteristics. TRIAL2 A 2 x 2 x 2 x 2 factorial arrangement of 16 dietary treatments was used to test the effects of a brown (Neche) vs. a golden (Omega) variety of flaxseed, ground vs. whole flaxseed, feed storage temperature (4 vs. 21"C), and two levels (27 vs. 50 IU) vitamin E supplementation on egg stability. Basal diets, like the diet shown in Table 1,included 10% flaxseed. Each diet was fed to four replicate pens with five 24-wk-old Babcock B300 laying hens per pen. Diets were fed for 6 wk, and eggs were collected for stability and sensory analysis at week 6. STABILITY AND COLOR ANALYSIS All eggs were candled and graded according to USDA standards, then refrigerated (12OC) for the duration of the study. To simulate commercial handling of eggs, test eggs were held in commercial egg cartons in a walk-in refrigerator. Stability was determined chemically by analyzing the egg yolk for levels of thiobarbituric acid reactive substances (TBARS) [14], using two duplicate samples per yolk. Results are expressed as mg TBARS/kg yolk. In 'Itial 1, five eggs per treatment were analyzed for TBARS after 2, 4, and 6 wk of refrigerated storage. In 'Rial 2, two replicates of two eggs per treatment were analyzed for TBARS at time 0 and after 8 wk of refrigerated storage.
Downloaded from http://japr.oxfordjournals.org/ at Georgetown University on May 23, 2015
as dietary alternatives to fsh [6]. As demand and production of these enriched eggs increases, research is needed to determine their stability and consumer acceptability during storage. The stability of foods during storage is indicated by the level of oxidation products, such as thiobarbituricacid reactive substances (TBARS). TBARS reflect the amount of oxidation that the constituent fatty acids have undergone [6]. During lipid oxidation unsaturated fatty acids oxidize, producing hydroperoxides capable of reacting with thiobarbituric acid to produce a colored (pink) complex which can be measured spectrophotometrically. Pike and Peng [7J reported no change in egg yolk TBARS during cold storage that lasted for as long as 12 to 18 months. They postulated that egg yolk has an unusual stability in terms of lipid oxidation. However, the eggs they tested were not enriched with 53-3 fatty acids, which could have less stability due to the increased levels of unsaturation. Recent investigations by Aymond and Van Elswyk [8] reported no changes in egg yolk TBARS in eggs from hens fed flaxseed. Yolk color can also be directly affected by dietary ingredients, particularly by the dietary xanthophyll content. Flaxseed varieties have potential to affect yolk color due to their varied levels and types of xanthophylls [9]. Several investigators [lo, 11,12, U]have shown that alteration of the Q-3 fatty acid content in egg yolk can affect the eating (sensory) quality of the egg. Koehler and Bearse [9] first reported lower flavor ratings for eggs produced from hens fed 5% fish meal, as well as a very slight off-flavor in eggs from hens on a 6% menhaden oil diet. More recently investigators [12] reported a difference in sensory evaluation of scrambled eggs vs. hard-cooked a-3fatty acid-enriched eggs; panelists could more readily distinguish the regular scrambled eggs from the hard-cooked Q-3-enrichedeggs. All of these sensory evaluations of GI-3 fatty acid-enriched eggs were conducted on relatively fresh eggs. Our studies sought to investigate the effects of dietary menhaden oil, flaxseed level, dietary flaxseed variety, flaxseed preparation (ground vs. whole), feed storage temperature, and level of dietary vitamin E on the stability of fresh and stored eggs. Stability was evalu-
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELERel al.
139
TABLE 1. Dietary composition and nutrient analysis
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*Menhaden fish oil was provided by Zapata Protein, Inc., Menhaden Oil Refinery, P.O. Box 175, Reedville, VA and was stabilized with W p p m ethoxyquin. %itamin E premix prmided an additional 50 W/kg vitamin E. %tamin/Mineral remix provided Mn,,88 mg; Cu, 6.6 m%;Fe, 8 5 mg; Zn,88 mg; Se,.O.? m ;vitamin A, 6,600IU; vitamin Dk 2,805 18;vttamin E, 10 IU; vltamm K,2.0 mg; nboflavin,4.4mg; pantothenicaad, 8.6 mg; niacin, 24.2 mg; choline, 110 mg,vitamin B1h 8.8 mg; ethoxyquin, 1.1 mg/kg.
140 Yolk color [15] was determined for eggs in Trial 2 only. Yolks from six eggs were separated from the whites and dried on a paper towel; two randomly selected yolks were then combined, giving three replications per treatment diet.
%all samples were prepared and evaluated on fresh eggs and eggs d e r 6 wk of refrigerated storage.In 'Itial2samples were evaluated on fresh eggs and eggs after 8 wk of refrigerated storage. A randomized complete block design was used for the sensory evaluations with blocking for panelists [18,19].
RESULTS AND DISCUSSION TRIAL 1 Dietary treatment effects on egg yolk fatty acid composition as reported by Scheideler and Froning [3] showed significant linear effects of dietary level of flaxseed on egg yolk 52-3fatty acid content. Diet significantly (P < .05) affected the level of oxidation (Table Z), as measured by TBARS, occurring in the eggs at all storage times (2,4, and 6 wk). Generally throughout the study eggs from the control diet had consistently lower TBARS values than the eggs from hens on the fish oil or flaxseed diets. Interestingly,the TBARS levels decreased (P< .01) over the 6 wk of storage. The reason for this time effect needs additional study, it may indicate the loss of active carbonyls due to reactions with other chemical components such as proteins, or antioxidant reactions occurring during storage. Eggs are very resistant to oxidative reactions due to natural antioxidant components, including egg yolk, vitamin E, avidin, and phosphatine [I. Within each test period, the effect of the flaxseed relative to the control was an increase in TBARS, especially at weeks where there seemed to be a linear increase in TBAFW associated with increasing percentage of flaxseed. The decrease in TBARS over time was consistent across all dietary treatment groups. Other researchers [SI have reported no significant treatment effect of flaxseed form (whole vs. ground) on egg yolk TBARS or of fish oil [6] on TBARS in eggs from hens fed 1.5% menhaden fish oil and stored for 0,2, or 4 wk. Results of seed preparation in this study are inconsistent, showing moderate effects of ground versus whole flaxseed on TBARS at 2 wk of storage only. When the eggs were evaluatedfor sensory attributes (Table 3) at time 0, results showed that eggs from hens fed the ground flaxseed, both 10 and 15% levels, were less (P< .OS) acceptable in appearance than the other treatment eggs. At 6 wk, eggs from the 10
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SENSORY EVALUATION Sensory evaluation utilized a descriptive scale for determining treatment effects on egg qualitylstability. All scales were 15 cm long; the scale rated the appearance, texture, and flavor, using 0 = very undesirable and 15 = very desirable. Off-flavor was measured where 0 = lacking and 15 = intense. Flavor was defined as typical "egg flavor;" the panelists defined off-flavor as any flavor other than egg. Overall acceptability was also included as a means of determiningthe potential "consumer" perception of the eggs, rated from 0 = very undesirable to 15 = very desirable. The nine panelists were recruited from graduate students at the Department of Food Science and Technology and the Department of Animal Science (University of NebraskaLincoln) [16]. To prepare the samples, three eggs per treatment were blended with 36 g whole milk for 30 sec using a hand blender. The blended egg mixture was poured into a heated (120°C) equilibrated (30 sec) teflon-lined electric skillet lightly coated with Pam cooking spray. Samples were cooked for 4 min with continuous mixing. After cooking, 10-g subsamples were placed into lidded plastic cups labelled with 3-digit codes. Samples remained in the refrigerator until all samples had been prepared and cooled to the same temperature, then reheated for 10 sec in a microwave. Preliminary work (data not shown) showed that this handling procedure did not af€ect sample evaluation. We established this procedure in order to prepare and serve the required number of sampleswhile assuring uniform product quality. Sample sets of four were served one sample at a time in a completeblock design so that each panelist tasted all samples. Treatments were replicated three times. All evaluations were performed in a controlled environment with panelists seated in individual lighted partitioned booths [17]. Panelists used room temperature water and unsalted-top crackers to clear their palates between samples. In
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELER et ai.
141
TBAR (m&
DIETARY TREATMENT
2 Wk
yolk)
4 Wk
6 Wk
Control
0.371'
0.29F
0.176'
0.473"
0.333'"
0.229
0.643'
0.29F
0.191''
5% Ground flaxseed
0.422'
0.268"
0.202d'c
10% Whole flaxseed 10%Ground flaxseed 15% Whole flaxseed
0.368'
0.326'*
0.224c3
0.432"
0.339'b
0.280ab
054Pb
0.366'
0.255"
15% Ground flaxseed
0.395'
0.362'b
0.295'
SEM
0.017
0.009
0.005
% Probability
df Diet effect
7
0.01
0.02
0.01
Time effect
2
0.01
0.01
0.01
DImARY TREATMENT
APPEARANCE* TEXTUREA
OWk I 6 W k
I Fishoil control I 5% Whole flaxseed I S%Groundflaxseed I lO%Wholeflaxseed I 10% Ground flaxseed I 15%Wholeflaxseed I Control
15% Ground flaxseed
9.03' 8.74' 8.69. 9.09" 85a"
7.41b 851' 7.16b
I 9.03a I 8.92' I 8.3Pb I 9.10' I 7MbC I 8.84' I 6.73"
8.40
8.61
8.76'
7.50
1
8.98
8.13 8.18 9.12 8.79
0.49
I I
I I
1
7.75 8.07
FLAVORA
I OWk
I6Wk
I 8.49a 1
858
OFF-
OVERALL ACCEPTABILITY/
FLAVOR^
I OWk
I6Wk
4.18
4.24
I
I 8.05' I 8.54 1
4.72
I
I I
451
I I
1
OWk 8.63 8.06
I
I
1
6Wk 8.478 8.3?
8.20
7.65
1 7.84' I 1 8.naI I 7.fl I
8.60
6LWb
8.60
5.61
4.36
6.92
8.7?
7.29
7.8?
7.23
4.88
6.37
7.79
7.13b
7.00
8.34
7.62 0.49
1
7Xb
0.42
I
7.30 8.36
8.47 0.42
I I I
5.95 455 4.79
I I
5.11
I
0.64
I
NS
I
454 5.11 5.08
5.19
I I I
7.69 8.41 7.72
7.42
0.64
I
0.43
NS
I
NS
I I I
7.95' 8.63' 8.32'
8.55'
I
0.43
I
0.05
Probabilitv
NS
Diet effect Timeeffect
I
I
NS
I
I 0.05
NS
I
0.05
I NS
NS
I 0.05
NS
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Fish oil control 5% Whole flaxseed
142
TRIAL 2 Table 4 shows dietary effects on TBARS production in eggs from Trial 2. There were no significant main effects of dietary treatment on TBARS at 0 or 8 wk of storage. There was a significant reduction in TBARS from 0 to 8 wk. This is similar to the effect of time on the reduction of TBARS found in W a l l . Although the decrease in TBARS was significant, it should be emphasized that all of the TBARS (0-and 8-wk storages) are relatively low. There was a significant interaction effect between variety of flaxseed fed and level of vitamin E supplemented, such that response to vitamin E supplementation varied according to variety of flaxseed. Vitamin E supplementation (50 IU/kg) lowered the TBARS at 0 wk in the golden variety and at 8 wk in the brown variety. The time effect of lowered TBARS between 0 and 8 wk was consistent between varieties and level of vitamin E fed.
SENSORY EVALUATION Table 5 shows the results of the sensory analysis of fresh eggs for 'Rial 2. Since there was no significant effect of storage time or interaction of time and diet effects in this trial, the second set of data (8 wk) are not given. Dietary effects on sensory evaluationin Trial 2 are limited to two treatment effects: variety on appearance and type of flaxseed preparation on texture. Eggs from hens fed the golden (Omega) variety of flaxseed had a higher ranking for appearance than the brown (Neche) variety of flaxseed, perhaps because of a different pigment composition in the two flaxseed varieties. 'Qpe of flaxseed preparation (whole vs. ground) had a significant effect on texture, with eggs from the whole flaxseed having a higher score than those from ground flaxseed. This observation of dietary flaxseed preparation effect on egg texture was not made in Trial 1's sensory analysis. Overall acceptability was not significantly affected by any of the dietary variables tested, but it should be noted that Trial 2 variables included only dietary flaxseed variety, preparation, storage temperature, and added vitamin E dietary flaxseed content remained constant at 10%. Table 6 shows the effects of Trial 2's dietary treatments on egg yolk color. Degree of lIghtness/darkness was significantly affected by variety of flaxseed (P < .01). The golden variety (Omega) of flaxseed produced a measurably lighter yolk than the brown (Neche) variety. This supports the appearance data in the sensory analysis study, similarly giving a higher ranking to eggs from the golden variety of flaxseed diets. Although not tested for, it appears that various varieties of flaxseed have different types of soluble pigments capable of incorporation into the egg yolk.
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and 15% whole flaxseed treatments had the least (P < .OS) acceptable appearance. Texture was not significantly different among treatments either at time 0 or at 6 wk. Flavor, i.e., "egg flavor," of the eggs from hens fed the ground flaxseed (10 and 15%) were less (P < .05) acceptable at time 0, but the effect did not occur at week 6. Off-flavor, i.e., flavor other than egg, was not affected by treatment at either 0 or 6 wk. Although there were differences in the acceptability of the eggs at time 0, these were not significant. However, at week 6 the eggs from the 15% whole flaxseed treatment were significantly (P < .05) less acceptable. Based on the data, fish oil and 5% levels of flaxseed did not affect the sensory acceptability of eggs; however, as the level of flaxseed increased, the eggs became less acceptable.
OMEGA EGG ACCEPTANCE
Research Report SCHEIDELER et al.
143
TABLE 4. Thiobarbituric acid reactive substances (TBARS) for eggs at 0 and 8 wk of storage time (Flaxseed, Trial 2)
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JAPR OMEGA EGG ACCEPTANCE
144
8.99
8.05
8.45
4.29
7.97
8.65
8.11
8.28
4.51
7.69
(P value)
0.01
NS
NS
NS
NS
Whole
8.76
8.32
8.28
4.28
7.78
Ground
8.85
7.85
8.45
453
7.88
(P value)
NS
0.05
NS
NS
NS
4.4"C
8.83
7.98
8.37
452
7.84
21.0"
8.81
8.18
8.35
4.29
7.82
(P value)
NS
NS
NS
NS
NS
27 IU&
8.94
8.13
8.36
4.22
7.78
50 IUjkg
8.70
8.04
8.37
459
7.88
(P value)
NS
NS
NS
NS
NS
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Golden Bl-OWIl
Research Report 145
SCHEJDELER et al.
Whole
4.4
50
525
(-)3.00
31.9
Golden
Whole
21.0
50
535
(-)255
32.3
Golden
Ground
4.4
50
53.1
(-)2.66
32.2
Golden
Ground
21.0
50
54.4
(-)253
32.4
SEM
0.42
0.15
0.20
Golden
53.6
(-)2.73
32.40
BlDWl (P value)
52.4
(-)2.78
32.11
NS
NS
0.01
Whole
52.9
(-)2.90
32.2
Ground
53.2
(-)2.61
32.3
(P value)
NS
0.05
NS
4.4"c
52.7
(-)2.81
32.2
21.0"c (P value)
53.4 NS
(-)2.70 NS
32.3 NS
27 IUkg
53.0
(-)2.88
32.3
50 IU/kg
53.1
(-)2.63
32.2
(P value)
NS
NS
NS
CONCLUSIONS AND APPLICATIONS 1. Omega-3 fatty acid-enriched eggs from hens fed 1.5% menhaden fish oil or 5% flaxseed have minimal effects on consumer acceptance compared to non-enriched eggs; dietary levels of 10or 15%flaxseed, however, have somenegative effectson appearance and flavor.
2. Oxidative products in stored eggs as measured by TBARS decrease during refrigerated storage up to 8 wk, but did increase in eggs from flax-fed hens. 3. Variety of flaxseed (golden vs. brown) can affect egg yolk appearance and consumer perception of scrambled eggs.
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Golden
JAPR OMEGA EGG ACCEPTANCE
146
REFERENCES AND NOTES 1. Van Elswyk, M.E, 1993. Designer Foods:Manipulatin the fatty acid composition of meat and e the f e a l t h conscious consumer. Nutrition E d 5 MarcWApril, pp. 21-27.
14. T.rlsdgis, B.G.,A.M.Pearson, and LR Dugan, Jr., 1964. Chemistry of the 2-thiobarbituric acid test for determination of oxidative rancidity in foods. J. Sci. Food Agnc. fi602-607.
2. Hargis P.S. and M.E Van ElsnyL, 1993. Manipulating the fatty acid composition of poult and meat and e g p for the health-conscious consumer. %orld’s Poultry Scl. 49251-264.
15.Yolks were blended for 30 sec then transferred to
5. Jiang, Z, D.U. Ahn, and J.S. Sim, 1991. Effect of feeding flaxseed and two of sunflower seed on fatty acid com osition of y o E p i d classes. Poultry Sci. 70:2457-2!75.
6. Mayshall, AC.,.A.R Sams, and M.E Van Ekwyk, 1994.Omdatrve stabilityand senso uality of stored e from hens fed 15% menhaden Food Sci. 5 9 5 e 563. 7. Pike,O.A. and1.C. Peng,1985.Stabili of shell e and liquid yolk to lipid oxidation. Poultry&. 64:14# 1475. 8. Aymond, W.M. and M.E Van m k , 1995. Yolk thiobarbituric acid reactive substances and 51-3 fattvacids nse to whole and ground flaxseed. Poultry Sci. kFx1394.
OX!.
having an L value of 95.47; and aL value of 0.61; and a b value of 0.40. L is lightneddarkness; a is a measure enness ) to redness (+); and b is a measure of $ l E e s s (+$ to blueness (-). 16. Panelists were familiarized with the rating form and scrambled egg samples in two 2-hr sessions nor to beginning the study. Trainin4 sam les were ma& using fresh commercial e g p obtained from a local grocery store. During training/familiarization panelists were seated at round tables and provided with necessary utensils, pencils, water, and unsalted-top crackers. Panelists were given three samples of scrambled e one at a time, in a randomized order. Panelists were a E 4 e d to work at their ownpaceandwere asked toevaluate t h e e p ymples using the provided form. After traininglfami ianzation, panelistsparticipated in a generaldiscussionto determine whether they had any problems using the forms to evaluate samples. 17.American Society for Testing and Materials, 1973. Standard Recommended Practices for Establishing Conditions for Laboratory Senso Evaluation of Foods and Averages. Committee E-18, $80. ASlX4, Philadelphia, PA.
9. Mayo, P . 5 , AR Spms, andM.E VmELFWyL, 1995. Yolk pigmentation in re me to dietary flaxseed seed. Poultry sci. 73(SuPpl):14Y 10. Kochler, H.H. and G.E Beprse, 1975. Epg flavor quality as affected by fish meals or fish oils in laying rations. Poultry Sci. Sk881-889. 11. A~OIUS,R L , D.L Pmtt, J.H. Lsn,andWJ. Stndelman, 1989. Introduction of omega-3 nsaturated fatty acids into eggs. Poultry sci. 68:166
g$.
12. Van Elswyk, M.E, AR Sams, and P.S. Har& 1992. Composition, functionality, and sensory evaluation from hens fed dietary menhaden oil. J. Food Sci.
19. SAS Imlitute, 1989. SASWAT User’s Guide. Version 6.4th Edition. Vol. 2. SAS Institute, Inc., Cary, NC.
ACKNOWLEDGEMENTS The authors would like to thank Lyle Robeson,
Lynn Niemann, and Minnie Stephens for their technical 13.Jiang,Af D.U.Anh,LLsdner,andJ.S. Sim, 1992. Influence of feeding full-fat flaxseed and sunflower seeds on internal and sensory qualities of e m . Poultry Sci. 71:378-382.
support in preparing this article. Financial sup ort of the North Dakota Oilseed Council is gratefup acknowledged.
Downloaded from http://japr.oxfordjournals.org/ at Georgetown University on May 23, 2015
3. Scheideler, LE and G.W. Froninp, 1996. The combined influence of dietary flaxseed variety, level, form, and storage conditions on egg roduction and composition among vitamin E. Poultry%. 75:1221-1226. 4. Caston, L and S. Letson, 1990. Research note: Dieta flaxseed and egg composition. Poultry Sci. 691617-1620.