淘汰蛋鴨卵巢卵黃利用性之研究

Abstract

本研究旨在利用不同溶劑對卵巢卵黃進行卵黃油及卵磷脂之萃取，再將卵磷脂以磷脂酵素D進行修飾，以提升磷脂醯絲胺酸（phosphatidylserine, PS）之含量，供作機能性之食品原料。蛋鴨卵巢卵黃先以0.17 M食鹽水沖洗乾淨後以100℃加熱7.5分鐘，加熱後打散以50℃乾燥4小時即為乾燥蛋黃。首先以六倍丙酮萃取可得蛋黃油，將殘留物再以六倍乙醇萃取可得高純度低膽固醇卵磷脂。將蛋黃油以5％之含量添加於還原脫脂乳（固形物12％）中經Lactobacillus helveticus 及Lactobacillus acidophilus 發酵後分別在18 小時及24 小時可提升5.2％及2.4％之共軛亞麻油酸含量。另添加1％亞麻油酸於發酵基質中，經L. helveticus 及L. acidophilus 發酵後分別在24 小時及18 小時可提升35.2％及38.5％之共軛亞麻油酸（conjugated linoleic acid, CLA）含量。卵磷脂則利用磷脂酵素D（phospholipase D）之磷脂轉移作用（transphosphatidylation）以提升磷脂醯絲胺酸含量。在不同溫度（20, 25, 30, 35, 40及45℃）對磷脂醯絲胺酸生成量之影響方面（圖5-5），於溫度在40℃及45℃有較佳之生成量，其含量分別為46.02 及39.03 μg/mL（p＜0.05）。在不同pH（4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5及8.0）之間以pH 5.5時有最佳之生成量42.29 μg/mL（p＜0.05）。於不同濃度之氯化鈣（0, 20, 40, 60, 80及100 mM）之間，濃度為40及60 mM之下有最高的磷脂醯絲胺酸生成量（p＜0.05），其含量分別為37.76及35.38 μg/mL，而氯化鈣濃度介於40至60 mM之間對磷脂醯絲胺酸之生成量並無影響。由前述之結果可知，利用磷脂酵素D來生成磷脂醯絲胺酸在pH 5.5、溫度40℃、氯化鈣濃度為50 mM以下有較佳之磷脂醯絲胺酸生成量，因此將實驗固定於此條件，探討適當的反應時間，當反應時間大於一小時，磷脂醯絲胺酸含量皆顯著上升（p＜0.05），並隨著時間增加而有上升之趨勢，並在24小時和48小時之間達到最高之磷脂醯絲胺酸含量（p＜0.05），其含量分別為56.36及53.19 μg/mL。

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.