Authenticity Determination of Bird’s Nests by Component Analyses
為瞭解市售燕窩品質，本研究利用燕窩成分特性鑒別燕窩之真偽。以顯微鏡鑒別燕窩形態，發現燕窩在顯微鏡下呈現無色透明、長方形或不規則的碎片，在表面及斷面處有細密的平行紋理，有的表面密佈細小圓孔或細顆粒狀物。市售乾品燕窩，粗蛋白質含量介於 52.1∼63.4%。燕窩乾燥粉末經酸水解，dansyl chloride 衍生化後，以毛細管電泳分析燕窩胺基酸組成。燕窩乾燥粉末以10％ tetramethyl- ammonium hydroxide 溶液70℃ 加熱溶解，以毛細管電泳分析燕窩及其摻偽品豬皮及魚膘的蛋白質指紋圖譜，乾品燕窩在15-23分鐘遷移時間區間含有六根特定波峰，與燕窩之摻偽品豬皮及魚膘有明顯不同，可有效鑒別燕窩真偽。利用 SDS 膠體電泳分析蛋白質分子量，以Bio-safe Coomassie stain 及PAS (periodic acid stain) 醣蛋白染色法進行染色，發現燕窩在SDS 膠體電泳呈現6∼7條譜帶，而且幾乎均是醣蛋白。
燕窩乾燥粉末以三氟醋酸（trifluoroacetic acid）將唾液酸、中性糖及糖胺水解後，以高效離子液相層析儀-脈衝式電流檢出器(High performance ion liquid chromatography with pulsed amperometric detector, HPAE-PAD) 分析燕窩中醣類的組成，燕窩醣蛋白之醣類組成平均含量， Fuc 0.44%， Rha 0.20%， GalN 4.2%， GlcN 5.3%， Gal 5.0% ，Man 0.75% 及 N-acetylnuraminic acid (Neu5Ac) 11.4%。本研究利用唾液酸換算冰糖燕窩產品中燕窩的含量，以Neu5Ac/GalN比值表示冰糖燕窩產品的品質。對照組乾品燕窩之 Neu5Ac/GalN比值為2.3-3.0，20件冰糖燕窩產品之Neu5Ac/GalN比值為0.03∼3.0。
In order to gain insights into the qualities of bird’s nests found in local market nowadays, the components of various bird’s nest samples were used in this study to determine their authenticity.
Optical microscopy of various types of dried bird’s nest samples showed that they are colorless and transparent, and their shapes are rectangular or irregular fragments. The cross-section profile of bird’s nets has closely-spaced parallel texture, and some have densely-distributed tiny round holes or tiny granulates on their surface. Commercially available dried bird’s nests typically contain 52.1~63.4% of crude protein. Dried bird’s nest powder was easily hydrolyzed in acid. The protein hydrolysate were then derivatized with dansyl chloride, and analyzed by capillary eletrophoresis (CE).
Dried bird’s nest powder was dissolved in 10% tetramethyl- ammonium hydroxide solution, heated at 70℃, and analyzed by CE. Six characteristic peaks of major protein components of bird’s nest were found in the interval of 15-23 min migration time, whereas the adulterant pork skin and isinglass did not show these six peaks. Thus, CE analysis of protein profile was found to be an efficient technique to determine the bird’s nest authenticity.
Protein molecular weight was analyzed by using SDS PAGE, where gels were stained by the Bio-safe Coomassie stain and PAS (periodic acid stain). There were found 6~7 bands in the SDS PAGE for bird’s nests; moreover, most of them were glycoproteins.
Trifluoroacetic acid was used to hydrolyze sialic acid, neutralsugars and aminosugars of bird’s nests, and then the hydrolysates were analyzed by high performance ion liquid chromatography with pulsed amperometric detector (HPAE-PAD). The results showed that the glycoproteins of bird’s nests contain 0.44% of fucose, 0.2% rhamnose, 4.2% galactosamine, 5.3% glucosamine, 5.0% galactose, 0.75% mannose and 11.4% N-acetylnuraminic acid(Neu5Ac). In this research, bird’s nest content of “bird’s nest in rock sugar syrup” products was assessed by converting it into its sialic acid equivalent. The Neu5Ac/GalN ratio signifies quality of the “bird’s nest in rock sugar syrup” products. The Neu5Ac/GalN ratio of control bird’s nest was 2.3-3.0, while for 20 specimens of “bird’s nests in rock sugar syrup”, Neu5Ac/GalN ratios ranged from 0.03 to 3.0.
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