牛奶、奶制品、乳制品中乳清蛋白检测方案(毛细管电泳仪)

HIGH PERFORMANCECAPILLARYELECTROPHORESIS SYSTEM DETERMINATION OF WHEY PROTEINS IN MILK SAMPLES INTRODUCTION One of the tests for authenticity of milk and dairy foods is the qualitative and quantitative composition ofwhey proteins and their ratio. Caseins dominate in cow’s milk before its processing (about 80% of total protein)， whereas caseins arealmost absent in the whey composition whose main components are the following： . B-lactoglobulins， a-lactalbumin. . bovine serum albumin. . immunoglobulins， lactoferrin and other minor proteins. It is known that the protein composition in heat treated (pasteurized or sterilized) milk substantially differsfrom that in raw milk. Of the two basic whey proteins it is B-lactoglobulin that is least resistant to heating. Ithas been ascertained that its content in powdered milk is small and decreases during long storage. The method developed by Lumex researchers is intended for measuring weight concentration of proteinsin whey using capillary electrophoresis (CE) technique. The obtained measurement results providesolutions of the following application tasks： record the whey protein pattern of cow's milk； ● reveal the presence of reconstituted milk in whole pasteurized milk； identify milk origin from various dairy cattle. MEASUREMENT METHOD The method is based on preliminary preparation of the whey， its subsequent separation and quantitativedetermination of proteins using the CE technique. The proteins are detected at a wavelength of 205 nm.Borate buffer with Tween 20 polymer additive is used as a background electrolyte. MEASUREMENT RANGE The measurement ranges of the weight concentrations of proteins in whey are listed in table below. Component Measurement range， g/l a-lactalbumin (a-LA) 0.01-100 B-lactoglobulin A (B-LG A) 0.02-10 B-lactoglobulin B (B-LG B) 0.02-10 ADVANTAGES OF THE CE TECHNIQUE As compared to chromatographic technique for determination of whey proteins， the CE technique showsthe following advantages： short time of analysis； no need for costly chromatography columns (fused silica capillaries tens of times less expensivethan specific HPLC columns are used in measurements)； capability of determination of various B-lactoglobulin isoforms. EQUIPMENT AND REAGENTS The following equipment and reagents are used in the measurements： CAPEL-105M capillary electrophoresis system； . a-lactalbumin， B-lactoglobulin A， B-lactoglobulin B， bovine serum albumin； . sodium hydroxide，reagent grade； hydrochloric acid， high purity grade； . boric acid， reagent grade； Tween20. Data acquisition， processing and output are performed using a personal computer running underWINDOWS XP/Vista/7 operating system with installed dedicated software for data acquisition andprocessing. EXAMPLES OF REAL ANALYSES SEPARATION CONDITIONS：Buffer： borate with TweeT20 additiveCapillary： Leff/Ltotal 40/50 cm， I.D. 50 umSample injection： 250 mbar*sVoltage： +25 kVDetection： 205 nm .9 mAU Whey protein pattern ofpasteurized milk Measurement results (g/l)： 1-a-LA(1.9) 2-B-LG B(1.1)3-B-LGA(1.5) Whey protein pattern of driedmilk 2 3 4 5 min The contents of this paper are subject to change without notice. The information in this leaflet is supplemental. To get more specific information on this method， please contact the developer of thismethod Lumex Instruments Ltd. LUMEX INSTRUMENTS Head Office： pr.Obukhovskoi Oborony，70， Bldg. 2， St. Petersburg， 192029 Russia Postal address： P..O..Box 1234， St.-Petersburg， 190000， Russia Tel.+7 (812)718-5390； E-mail： lumex@lumex.ru； www.lumex.biz WWW.LUMEX.BIZ 乳品和乳制品的真实性鉴别方法之一就是通过乳清蛋白的定性和定量组成及其比值来确定的。酪蛋白在牛奶加工前占主导地位（约占蛋白质总量的80%），而乳清成分几乎不存在酪蛋白，其主要成分如下：β-乳球蛋白，α-乳白蛋白，牛血清白蛋白，免疫球蛋白，乳铁蛋白和其他次要蛋白质。众所周知，热处理（巴氏杀菌或灭菌技术）后牛奶中的蛋白质成分与原料奶基本不同。在这两种乳清蛋白中，β-乳球蛋白是最不耐热的β-乳球蛋白。已确定其在奶粉中的含量很小，并且在长时间储存之后会逐渐减少。LUMEX研究人员开发的方法是用毛细管电泳（CE）技术测定乳清中蛋白质的质量浓度。可以提供以下应用任务的解决方案：1.记录乳清乳清蛋白图谱；2.揭示整个巴氏杀菌乳中复原乳的存在；3,。识别各种奶牛的奶源。