مقایسه کیفیت داخلی و خارجی، ترکیب شیمیایی و ترکیب اسید چرب تخم مرغ مروارید (Numida meleagris) و تخم‌‌مرغ

Introduction: The term “guinea fowl” is the common name of the seven species of gallinaceous birds of the family Numididae, which is originated from Africa and their meat and eggs are very popular. Eggs, one of the versatile foods, inexpensive and high nutritious, supply well balanced nutrients that affect human health. An egg is a rich source of protein and then have high biological value. Eggs contain essential proteins, fats, vitamins except vitamin C, minerals mainly including calcium, phosphorous, iron, magnesium, zinc, selenium, potassium and sodium, and bioactive compounds, and their compositions could be affected by type of bird, heredity, strain, age, hen diet, and environmental conditions such as season and rearing condition. An average weight of egg in commercial strains is usually 55 g and this trait mainly influenced by diet mainly the concentration of methionine and lysine and energy content. Distribution of proteins in egg component is equal between egg yolk and egg white. Other hands, the egg yolk is the major part of lipid, mineral and vitamins. The high consumer preferences of guinea fowl and its products demonstrate that guinea fowl is valuable and have high marketing potential. Compared to native hens and chickens, the guinea fowl’s benefits are: low production and rearing cost, high meat quality, greater capacity to scavenge for insects and grains, better ability to protect itself against predators and low incidence of common poultry diseases than chickens including parasites Newcastle Disease and Fowl Pox. In order to improving household protein supply and income and Because of the great potential for increasing guinea fowl production for smallholder farmers need to evaluate their products and specifically egg. This study was conducted to determine internal and external egg quality traits, chemical composition and fatty acid profile of yolk of East Azarbaijan province guinea fowl and compare their values with table hen eggs values.
Material and methods: A total of 50 clean eggs were obtained from Bonab guinea fowl research station by simple random sampling method. The guinea fowl breeders were at the same age and fed with similar diets. In order to compare of these values with table eggs values, 50 clean table eggs were purchased from a market. After sampling, the eggs were immediately transferred to the lab and internal and external egg quality traits were individually measured. Descriptive statistics of traits were determined using SAS software by univariate procedure and unpaired t-test was used to compare the data of guinea fowl eggs with table eggs data.
Results and discussion: The results of this study showed that the mean external egg quality traits of guinea fowl eggs such as egg weight, shell ratio and thickness, egg shape index and egg volume were 40.736 g, 15.604% , 0.718 mm, 78.801 and 42.035 cm³, respectively. The mean of internal egg quality traits of guinea fowl eggs such as yolk and albumin percentage, haugh unit, yolk color, pH of yolk and albumin were 31.418%, 52.977%, 78.030, 8.80, 6.592 and 9.332, respectively. Also, the average external egg quality traits of table eggs such as egg weight, shell percentage and thickness, egg shape index and egg volume were 61.371 g, 9.080 %, 0.665 mm, 76.852 and 63.065 cm³. The mean of internal egg quality traits of table eggs such as yolk and albumen percentage, haugh unit, yolk color, pH of yolk and albumen were 31.334%, 59.585%, 75.075, 4.70, 6.431 and 9.415, respectively. The average of shell thickness of guinea fowl eggs were higher than hen eggs that indicate the shell strength of guinea fowl eggs is higher than table eggs. For determinating of chemical composition of guinea fowl and table eggs, 5 mixed samples (from each 10 eggs) were prepared. The amounts of albumin and yolk dry matter, albumin and yolk crude protein, yolk ether extract, and ash contents of shells were 13.526 and 46.662, 81.696 and 33.652, 31.456, and 89.924%, respectively and these values in table eggs were 12.730 and 45.770, 84.384 and 33.064, 30.406 and 77.564, respectively. The ash content of egg shells in guinea fowl was higher than that of table eggs. This is consistent with shell ratio and shell weight. Cholesterol content of the guinea fowl and table eggs were 1605 and 1391 mg/100 g of yolk, respectively. To determine the fatty acid profile of egg yolk of guinea fowl and table eggs, 5 mixed samples were selected and the fatty acids contents were measured by the gas chromatography method. In guinea fowl, the highest fatty acids content of egg yolks were palmitic acid, oleic acid and linoleic acid, with the amounts of 28.274%, 34.686% and 20.130% of total fatty acids of egg yolk, respectively. The highest and the lowest fatty acid content of table egg yolks were palmitic acid and docosapantaenoic acid with values of 29.176 and 0.026, respectively. The sum of saturated fatty acids (SFAs), monounsaturated fatty (MUFAs) acid and polyunsaturated fatty acids (PUFAs) in the egg yolk of guinea fowl were 38.144, 38.712 and 22.090 % and for table eggs were 40.638, 32.280 and 19.361 %, respectively. The sum of PUFAs of guinea fowl eggs significantly higher than table eggs (p < 0.05). Sum of n-3 PUFAs in table eggs was higher than guinea fowl eggs (0.567 vs 0.342) and unlike n-6 fatty acids, the guinea fowl eggs had higher value in comparison of table eggs (21.746 vs 18.694). PUFAs and specially, n-6 PUFAs have a hypo-cholesterolemic effect than n-3 PUFAs and therefore guinea fowl eggs can decrease cholesterol content of serum.
Conclusion: According to the results, the level of cholesterol, n-6 fatty acids and n-6 to n-3 fatty acids ratio of guinea fowl eggs were higher than those of table eggs. Also, the sum of PUFAs and the sum of SFA to sum of MUFA ratio in yolk samples of guinea fowl eggs in comparison with table eggs were higher.