Study on the Utilizations of Ova Yolks from Spent Laying Duck
Date Issued
2007
Date
2007
Author(s)
Chen, Cheng-Hsing
DOI
zh-TW
Abstract
One-fifth of laying hens are replaced by new ones each five months with forced moult for the reason of keeping egg price and production steady. Spent laying hens still have ova yolks at various developing stages and there’s no difference between ova yolks and conventional egg yolks in neither chemical compositions nor functions. The object of this study is to separate lecithin and yolk oil by different solvents from ova yolks and lecithin is further modified by phospholipase D to increase phosphatidylserine content.
Duck ova yolks were washed by 0.17 M salt solution and boiled for 7.5 minutes, then dehydrated at 50℃ for 4 hours. Yolk oil was available after extracted by 6 volumes of acetone about ten minutes. Lecithin with low cholesterol content was extracted by ethanol from dehydrated ova yolk acetone insoluble. Yolk oil is fermented by Lactobacillus helveticus and Lactobacillus acidophilus as 5% yolk oil added in 12% skim milk to produce fermented milk rich with conjugated linoleic acid (CLA). CLA content increased when fermented 35.3% in 24 h by L. helveticus and 38.5% in 18 h by L. acidophilus. Lecithin is modified by transphosphatidylation of phospholipase D ( PLD ) to increase phosphatidylserine content. At different temperatures between 20 to 45℃, phosphatidylserine had highest content at 40 and 45℃; and they were 46.02 and 39.03 μg/mL respectively. In different pH value from 4 to 8, phosphatidylserine had highest content at pH 5.5 and it was 42.29 μg/mL. Calcium chloride concentration also affects phosphatidylserine content. It had higher phosphatidylserine content in 40 and 60 mM, which produced 37.76 and 35.38 μg/mL of phosphatidylserine respectively. But, the phosphatidylserine content had no significant difference among the concentration from 40 to 60 mM of calcium chloride. Finally, the conditions are kept at 40℃, pH 5.5 and 50 mM calcium chloride in order to determine suitable reaction time. The phosphatidylserine content raises after one hour and it’s content increased as the reaction time increased till the end of experiment. The highest phosphatidylserine content occurred during the reaction time at 24 and 48 h and their phosphatidylserine contents were 56.36 and 53.19 μg/mL respectively.
As the aforementioned result described, the favorable condition to increase phosphatidylserine content by transphosphatidylation of phospholipase D was at the pH 5.5, 40℃, 50 mM calcium chloride and the reaction was 24 h. This experiment has made a suitable utilization of ova yolk from spent duck ova yolk by separating lecithin and yolk oil. Lecithin is modified by phospholipase D for the synthesis of phosphatidylserine and also provides additional value of ova yolk.
Subjects
卵巢卵黃
卵磷脂
磷脂醯絲胺酸
磷脂酶
D
共軛亞麻油酸
Ova yolk
Lecithin
phosphatidylserine
phospholipase D
conjugated linoleic acid
Type
thesis
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