And the increasing content of CLA in yolk did not affect taste, odor, appearance, overall acceptability and hardness of hard boiled eggs, said the authors, who published their work in the journal Food Chemistry.
“The phenomenon, that eggs naturally enriched with CLnA preserve their composition and conventional properties, has been reported for the first time. Further studies are needed to determine [the] optimal amount of pomegranate seed oil (as source of CLnA) in hens’ diet to obtain high quality eggs with ‘health effective’ content of CLnA as well as CLA,” said the researchers, based at the University of Agriculture in Kraków and Poland’s National Research Institute of Animal Production.
They said there is considerable interest in supplementing feed with CLA as it has been shown to result in many health related effects for consumers, such as reducing carcinogenesis, atherosclerosis, diabetes, and body fat mass as well as modulating the immune function (Kim et al., 2016).
However, the authors cited previous work indicating some parameters of egg quality are aggravated when hens were fed a diet with CLA oil.
A previous trial, they noted, had shown that CLA enriched eggs had anti-atherogenic properties. However, the researchers said the physicochemical properties of such fortified eggs were negatively changed - the hardness of egg yolk was increased.
But, in another study, the Polish team said when CLA was combined with some other fatty acids simultaneously, the quality of eggs was improved (Kim et al., 2007). “It was observed that shell thickness, shell strength, yolk color, yolk index, egg diameter, and Haugh units were aggravated when CLA was fed alone, but the quality was improved when CLA was combined with some other fatty acids.
The egg production rate, which was decreased by feeding CLA alone, was improved by co-supplementation with linoleic acid (LA) or oleic acid (OA). An increase in CLA content was seen in all the dietary groups fed CLA for 2 weeks. However, egg yolks from hens given CLA had considerably higher amounts of saturated fatty acids and lower amounts of monounsaturated fatty acids than egg yolks from the control group.”
The researchers said the aim of this study was to evaluate a new potential source of fatty acids with pro-healthy properties that could be incorporated into egg yolks without changing the quality of eggs.
The team said they gave 40 Isa Brown laying hens a commercial layer diet comprising 2.5% sunflower oil (control) or three levels (0.5, 1.0 and 1.5%) of punicic acid in the diets.
After 12 weeks of feeding the hens, the researchers collected the eggs. They said they analyzed 60 eggs – randomly selected from each group – for physicochemical properties.
The Polish researchers found dietary CLnA had a positive impact on the color of the eggs’ yolk, whereas the hardness of hard-boiled egg yolks was not affected.
Additionally, increasing dietary CLnA led to an increase not only the CLnA concentrations, but also CLA in egg-yolk lipids, they said.
The researchers concluded: “In our study, it was shown for the first time that in eggs received from hens fed diets with pomegranate seed oil, not only CLnA, but also CLA were significantly increased.
We have shown that hens fed with CLnA positively influenced the eggs weight and eggs yield.
Additionally, the Haugh units and pH value were similar to the control ones and were typical for fresh eggs.”
Moreover, they said the CLnA-enriched eggs could be also a good source of nutrients: “Protein, fat and ash share in dry matter of these eggs did not different to control ones. Interestingly, hens’ feeding with pomegranate seed oil enriched food more effectively incorporated CLA into egg yolk lipids than food enriched in CLA oil – when compared with the results of our earlier studies (Franczyk-Zarow et al., 2008).”
They also said their study demonstrated that the cholesterol content in egg yolk was decreased after increasing the pomegranate seed oil level in the diets. “Greater concentration of CLnA in food resulted in a significant reduction of the cholesterol level,” added the team.
Source: Food Chemistry
Published online ahead of print: doi.org/10.1016/j.foodchem.2016.11.051
Title: Effect of dietary pomegranate seed oil on laying hen performance and physicochemical properties of eggs
Authors: RB Kostogrysa, A. Filipiak-Florkiewiczb, K. Dereńb, A. Drahuna, I. Czyżyńska-Cichońa, E. Cieślikb, B. Szymczykc, M. Franczyk-Żarówa