Citation of this paper

Effects of omega-3 fatty acids enrichment with flaxseed oil and egg storage duration on egg quality

C A Brown, J A Hamidu, K Adomako and M A Okai

Department of Animal Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
jahamidu.canr@knust.edu.gh

Abstract

Feeding laying chickens can influence egg quality and increase market value. The objective of the current study was to determine egg quality as the level of flaxseed oil increased in poultry diet in omega-3 egg enrichment study. A secondary objective was to determine impact of increasing storage duration of eggs over a period of 14 days on egg quality. The study involved the enrichment of chicken eggs with the inclusion of varying levels of flaxseed oil in layer diet. Eighty commercial Lohmann tradition layers (n=20 per treatment) were randomly allotted to 4 isocaloric and isonitorogenous dietary treatments with varying levels of flaxseed oil (control (0%), 1.5%, 3% and 4.5%) from 39 to 70 weeks of age. Between 45 and 52 weeks of age, 900 eggs were collected for egg quality analysis. Fifteen eggs from each treatment were collected over 15 consecutive days. The eggs were stored at room temperature for zero to fourteen days. Afterwards eggs were broken to determine egg component characteristics. The data was analyzed using the SAS Proc. GLM procedure and lsmeans separated by the PDIFF procedure of SAS at P<0.05. The Haugh unit value, which is a measure of protein quality in the albumen of eggs was 81.2% in the 3% flaxseed oil treatment compared to the rest of the treatments: control (81.0%), 1.5% treatment (79.9%) and 4.5% treatment (80.8%). The treatment with 4.5% flaxseed oil had heavier egg weight compared to the rest. When eggs were stored over a period of 14 days in ambient temperature there was strong reduction in albumen quality and Haugh unit with increasing days of egg storage, an indication of increasing loss of carbon dioxide and moisture from the eggs. There was no significant effect of feeding treatments using different flaxseed levels on egg quality parameters except the yolk color which became pale with increase flaxseed oil inclusion. It can be concluded that enriching eggs with flaxseed oil will not change storage quality but storing eggs over prolonged period of time had the most negative impact by reducing egg quality.

Key words: albumen height, ambient temperature, Haugh value

Introduction

Egg provides a good source of high quality protein and contains many vitamins and minerals. Eggs in diets can also improve human health by preventing heart diseases, improving skin and hair, and boosting brain development (Wahlqvist 1998). However, the food value of eggs can be influenced by the formulation and composition of layer diets (Van and Huyghebaert 1995). This has led to several interested researchers in the production of nutrient enriched eggs. Several experiments however, for most parts in the western nations have been directed on enrichment of omega-3 (n:3) unsaturated fats in eggs and the production parameters of layers (Cherian et al 2002; Bean and Leeson 2003; Mazalli et al 2004; Jia et al 2008), egg quality (Galobart et al 2001; Ajuyah et al 2003; Cherian 2008), sensory evaluation (Ahn et al 1996; Gonzalez-Esquerra and Leeson 2000; Rymer and Givens 2005) and health benefits (Lewis et al 2000; Payet et al 2004).

However, a study on enriched eggs production and their effect on egg quality and consumer acceptability in Sub-Saharan Africa where this nutrition is crucially needed is limited. Indigenous studies on this research is vital as accessibility of feed ingredients used to produce these “designer” eggs are different in various regions of the World. Locally accessible ingredients might give a chance of more economical generation of these designer eggs. Numerous commercial organizations are creating a few assortments of omega-3 eggs or designer eggs which are accessible at premium costs in developed countries. Yet their strategy for production stays patented and sometimes as a business mystery which is not available for repetition in poor countries whose citizens need these eggs due to their poor eating habits, especially children.

Additionally, the storage and handling of eggs need to be well balanced to preserve egg quality and reduce spoilage. In most developing countries, the handling of table eggs is such that they are mostly kept in ambient temperature for several days on market shelves and even in homes. Proper storage of eggs such as in freezers however, is essential to preserve quality and cooking characteristics. It has been reported that poor storage conditions can reduce egg grade such as the albumen quality and reduce its shelf life within a few days (Tabidi 2011). The principle degrading factors are high storage temperatures and humidity leading to various degrees of dehydration and hastening of the spoilage process (Tabidi 2011; Feddern et al 2017; Chaudhary et al 2017).

Improper temperature of storage of eggs can introduce some observable changes. These include a change of thick albumen to watery albumen, enlargement of yolk that breaks easily when the shell is broken as a result of diffusion of water into the yolk, enlargement of the air cell, and absorption of off odors and off-flavors if stored near pungent foods (Tabidi 2011). Prolong storage in ambient temperature could also expose eggs to bacteria contamination. Hence the objective of this research was to add new information on the impacts arising out of the development of n:3 designer eggs as well as determine egg quality characteristics as the level of flaxseed oil used in omega-3 eggs enrichment increased in the poultry diet, as well as egg storage duration impacts on eggs over a period of 14 days in ambient temperature.

Materials and methods

Experimental diet and experimental design

One thousand Lohmann Tradition layer day old chicks were obtained from a commercial hatchery, Akate Farms and Trading Company Limited in Kumasi. The chicks were brooded for six weeks and fed a commercial starter mash with 20% crude protein and a metabolisable energy content of 2780 kcal/kg for six weeks. The birds were transferred to a grower diet from seven weeks until eighteen weeks of age. The ration had a crude protein of 17% and 2750kcal/kg metabolisable energy (calculated). The birds were again placed on a layer diet which was the same as the control diet (Table 1) during experimental allocation from week 20 until experimental logistics were ready for the study. At 39 weeks of age 20 birds each were randomly selected and allocated to four experimental diets containing varying levels of flaxseed oil: T1 (0%), T2 (1.5%), T3 (3%) and T4 (4.5%) in a Completely Randomized Design (CRD) (Table 12).

Each treatment was repeated once and each replicate represented an experimental unit. The birds were given a period of two weeks after placement on the experimental diets to adjust to the treatments before egg were collected for analysis. Feed and water were given ad-libitum throughout the experiment. Vaccination and medication schedules were strictly adhered to until completion of experiment. The vaccination schedule included vaccinating against Gumboro, Fowl pox and New Castle disease at scheduled times while dewormer and Sulphur powder (lice treatment) were given on schedule or when needed. Strict biosecurity measures involving all-in all-out procedures were practiced during the research period to maintain birds in healthy state.

Data Collection

Egg quality analysis was carried out at the embryology laboratory at the Department of Animal Science, KNUST. A total of 900 eggs were collected between week 45 and 52 for the egg quality analysis. Fifteen eggs from each treatment were collected on 15 consecutive days. The eggs were stored at ambient temperature for zero to fourteen days. The eggs collected were weighed and carefully broken by cracking the narrow anterior part of the oval shape to allow the easy flow out of the albumen. The albumen height was measured using the tripod micrometer after pouring the content of each egg on a completely flat surface. The highest portion of the albumen close to the chalaza was measured. The yolk was carefully separated from the albumen and weighed on an electronic scale.

Table 1. Percent composition of experimental diets and calculated nutrients components
Ingredients	Treatment with inclusion levels (%)
Ingredients	T1 (Control)	T2	T3	T4

Maize	61.8	57.3	52.4	47.7
Fishmeal	9.60	8.00	7.58	7.40
Soyabean meal	11.6	15.0	15.0	15.0
Wheat bran	9.00	9.00	13.4	16.7
Oyster shell	7.50	8.70	8.21	8.22
Flaxseed oil	0.00	1.50	3.00	4.50
Vitamin Premix	0.25	0.25	0.25	0.25
Salt	0.25	0.25	0.25	0.25
*Calculated nutrient composition (%)*
Crude protein	17.0	17.0	17.0	17.0
Metabolisable energy (Kcal/kg)	275	275	275	275
Calcium	3.29	3.50	3.50	3.50
Phosphorus	0.25	0.25	0.24	0.23
Crude fiber	2.93	3.28	3.36	3.60
Lysine	1.00	1.00	1.00	1.00
Methionine	0.37	0.35	0.35	0.34
Cysteine + methionine	0.69	0.64	0.64	0.63

The egg shell was gently washed over the eggshell membrane. The eggshell and the eggshell membrane were allowed to air dried for two days. The shell weight was taken using an electronic scale. The albumen weight was calculated as the difference between the weight of the egg and the weight of the yolk plus shell. The wet and dry components (yolk and shell) and albumen were expressed as percentage of the initial egg weight. The dry weight was determined by placing yolk and shell inside an electric oven for 3 days at 90^oC. Haugh unit was calculated using the formula of Haugh (1937); HU= 100 * log (h - 1.7w^0.37+ 7.6) where HU is the Haugh unit, h is the albumen height in millimeters and w is the egg weight in grams. The yolk colour was measured using the Roche colour fan (RCF 193).

Statistical analysis

Data collected were analyzed with the Generalized Linear Model Procedure of SAS version 9.4 (SAS Proc GLM) at P < 0.05. The lsmeans were separated by the Students Newman Keuls test (SNK) (SAS Institute 2012).

Results and discussion

Table 2. Effects of incorporating flaxseed oil in layer diet and egg storage duration in ambient temperature on external egg quality
Flaxseed oil inclusion	Initial egg weight (g)	Final egg weight (g)	Wet shell weight (%)	Dry shell weight (%)

T1 (Control)	61.4^b	60.9^bc	10.6^a	10.5^a
T2 (1.5%)	61.8^b	61.1^b	9.79^b	9.63^b
T3 (3%)	60.7^b	60.1^c	10.1^b	9.92^ab
T4 (4.5%)	63.8^a	62.9^a	9.87^b	9.94^ab
SEM	0.35	0.32	0.19	0.22
*Egg storage duration, days*
0	61.8^abc	61.8^ab	9.86^b	9.77^ab
1	62.3^ab	62.2^ab	10.4^ab	10.1^ab
2	59.3^c	59.0^c	9.62^b	9.48^b
3	62.6^ab	62.4^a	10.1^ab	9.98^ab
4	62.9^ab	62.6^a	10.1^ab	9.99^ab
5	59.9^bc	59.1^c	9.36^b	9.23^b
6	62.6^ab	62.2^ab	10.2^ab	10.0^ab
7	62.5^ab	61.9^ab	10.4^ab	10.2^ab
8	63.3^a	62.6^a	10.2^ab	9.99^ab
9	62.6^ab	61.4^ab	9.99^ab	10.6^ab
10	62.6^ab	61.7^ab	10.3^ab	10.1^ab
11	60.6^abc	59.5^bc	9.32^b	9.22^b
12	62.9^ab	61.7^ab	10.1^ab	9.87^ab
13	62.4^ab	62.2^ab	11.6^a	11.6^a
14	60.8^abc	58.9^c	9.82^b	9.69^ab
SEM	0.68	0.62	0.38	0.44
*Source of variation*
Flaxseed oil inclusion	<.0001	<.0001	0.013	0.064
Egg storage	<.0001	<.0001	0.015	0.053
Interactions	0.660	0.669	0.407	0.362
^abc Different superscripts within the same column indicate significant differences among means (P ≤ 0.05); initial egg weight is the weight of the egg on the day of lay; final egg weight is the stored egg weight, wet shell weight is the weight of the shell when it was air dried for three days and dried shell weight is the weight of the shell when it was oven dried at 90^oC for three days.

The effects of different flaxseed oil treatments were statistically significant (P<0.05) for initial egg weight, final egg weight, wet shell weight and dry shell weight when compared with the control. Treatment with 4.5% flaxseed oil recorded a significantly higher stored egg weight than the other treatments followed by treatment with 1.5% flaxseed oil. There was no difference between treatments with no flaxseed oil and treatments with 1.5% and 3% flaxseed oil. However, treatments with 1.5% flaxseed oil recorded a higher stored egg weight than treatment with 3% flaxseed oil. It was noted from this study that final egg weight was lower than the respective initial egg weights when compared. This increase in egg weight agrees with Jensen et al (1958), who stated that dietary lipids enhances the weight of eggs. Other studies that fed flaxseed to layer hens found significant differences in egg weight (Dunn- Horrocks et al 2011; Cherian and Quezada 2016). In related studies however, there were no significant difference in the egg weight of flax fed birds as compared to egg from birds which were not fed with flaxseed (Baucells et al 2000; Schumann et al 2000; Grobas et al 2001; Celebi and Utlu 2006). Similarly, Pappas et al 2005 and Augustyn et al 2006, found a negative effect of n:3 PUFA on egg weight.

Duration of egg storage can affect egg weight. This is because carbon dioxide (CO₂) and moisture are lost from an egg as it ages. This loss of CO₂ is rapid when eggs are stored in ambient temperature hence causing a decline in egg weight. From table 2 it can be noted that egg weight declined when eggs were stored for longer duration. There was a drop of 0.1g when eggs were stored for one day, the drop in egg weight increased to 0.73g when storage period increased to 8 days and 1.86g loss in weight when eggs were stored for 14 days. The trend indicates the effect of prolong storage of eggs on egg quality. There was a significant (P<0.05) difference between eggshell weight relative to egg weight (% wet shell weight) between the control diet and diet with flaxseed oil. Percent wet shell weight was lowest in eggs from hens fed with flaxseed oil. There was a significant difference in shell weight as egg storage duration increased.

Flaxseed oil did not have any significant effect on yolk weight relative to egg weight (% wet yolk weight), albumen weight relative to egg weight (% albumen weight), albumen height and Haugh unit when compared with the control (Table 3). A significant increase was recorded for percent wet yolk weight as storage duration increased. As storage duration increases, water is lost from the albumen to the egg yolk making it increase in size and heavier. This loss of water from the albumen into the yolk decreases the albumen weight with long storage duration. Even though there was no significant increase in percent albumen weight, it can be seen from table 3 that, albumen weight kept declining as storage duration increased. There was a significant reduction in albumen height as storage duration increased. This is because, as egg ages, carbon dioxide (CO₂) is lost from the egg through the shell pores by simple diffusion. This increases the pH of the albumen making it alkaline (Scott and Silversides 2000).

This causes the gelly-like albumen to become watery and transparent because mucin fiber a substance which gives eggs its gel-like texture is lost as CO₂ (Mountney 1976). The decrease in albumen height with storage agrees with the findings of Falvey et al (1998) and Samli et al (2005). A reduction in albumen height with storage will directly affect Haugh unit as egg ages. There was a significant decrease in Haugh unit from 95.4 in one-day old stored eggs through to 75.7 on the eighth day of storage to 63.09 when eggs were stored in ambient temperature for 14 days. It can be seen that 13 and 14 days stored were below the recommended HU for egg freshness of 70 HU.

The poorer quality of eggs with increasing storage in ambient temperature is shown by the strong positive coefficient of regression of 0.96 (Figure 1). Since the Haugh unit is determined by the thickness of the albumen, eggs that lose a lot of water and CO₂ following prolong storage have thinner albumen. This contributes to the loss of egg quality.

Table 3. Effects of incorporating flaxseed oil in layer diet and egg storage duration in ambient temperature on internal egg quality
Flaxseed oil inclusion	Wet yolk weight (%)¹	Albumen weight (%)²	Albumen height (mm)³	Haugh unit⁴

T1 (Control)	27.8	64.5	6.89	81.0
T2 (1.5%)	26.9	62.3	6.79	79.9
T3 (3%)	26.9	61.9	6.89	81.2
T4 (4.5%)	26.3	62.6	6.94	80.8
SEM	0.54	1.35	0.07	0.51
*Egg storage duration*
0	24.7^b	65.5	9.28^a	95.5^a
1	25.2^b	64.3	9.26^a	95.3^a
2	26.4^b	63.5	8.69^b	93.3^ab
3	26.5^b	63.1	8.20^c	89.8^cd
4	26.3^b	63.2	8.43^bc	90.6^bc
5	25.9^b	63.5	7.60^d	87.3^d
6	27.5^ab	61.6	6.91^e	81.9^e
7	26.9^b	61.6	6.81^e	81.1^e
8	26.7^b	61.9	6.09^f	75.7^f
9	26.6^b	61.5	5.65^gf	72.4^gf
10	28.1^ab	60.3	5.63^gf	72.6^gf
11	27.5^ab	61.5	5.27^gh	70.9^g
12	27.4^ab	60.7	5.78^f	73.9^gf
13	31.5^a	70.4	5.09^h	67.6^h
14	27.8^ab	59.6	4.46ⁱ	63.1ⁱ
SEM	1.05	2.62	0.13	0.98
*Source of variation*
Flaxseed oil inclusion	0.251	0.533	0.515	0.338
Egg storage	0.007	0.452	<.0001	<.0001
Interactions	0.756	0.414	0.275	0.273
abcdefgh Different superscripts within the same column indicate significant differences among means (P ≤ 0.05); wet yolk weight is the weight of the fresh egg yolk

Figure 1. Relationship between egg storage duration in ambient temperature and Haugh unit as egg quality
indicator. A lower Haugh unit is an indication of lowering protein quality in the egg.

Eggs from treatments with 0%, 1.5% and 3% flaxseed oil had appeared to have higher yellowish yolk as compared to eggs from treatment with 4% flaxseed oil (data not shown). The yellow color of egg yolk is normally derived from xanthophyll pigment in the hen’s diet. The lighter egg yolk recorded in this study can be due to less of these xanthophyll in the hen’s diet. Yellow maize was used throughout this research. Since portion of maize was replaced with flaxseed oil this could be the reason for the lighter egg yolk recorded in treatment with 4.5% flaxseed oil. The result of this study agrees with a previous study by Cherian and Quezada (2016) who recorded a paler yolk in eggs from treatment with flaxseed with a 9% drop in maize when compared with their control.

Conclusion

Flaxseed oil inclusion did not have any significant effect on both the internal and external quality parameters of eggs except the yolk colour which was expected.
Prolonged storage of eggs in ambient temperature reduced the protein quality which could affect shelf life of eggs negatively. It is concluded that storing eggs in ambient temperature will reduce eating quality and affect market value.

Acknowledgement

Our greatest appreciation goes to the Grand Challenge Canada under the Saving Brian Programme for funding the research component and its outreach project. Special thanks to the proprietor of V.O.A.-LYS FARMS LIMITED, Mr. Victor Oppong Agyei for building a poultry structure to support the study. Our appreciation also goes to Dr. O. S. Olympio, Mr. Roland Adama, Dr. Edusei, Miss. Victoria Kyeiwaa, Yaw Osei Bonsu and all teaching assistants and students for their volunteer work on the project.

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Received 8 November 2017; Accepted 2 February 2018; Published 1 March 2018

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