Determinación de proteínas de suero en muestras de leche por electroforesis en gel capilar

INTRODUCTION

One of the tests for authenticity of milk and dairy foods is the qualitative and quantitative composition of whey proteins and their ratio. Caseins dominate in cow’s milk before its processing (about 80% of total protein), whereas caseins are almost absent in the whey composition whose main components are the following:

• β-lactoglobulins,
• α-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 differs from that in raw milk. Of the two basic whey proteins it is β-lactoglobulin that is least resistant to heating. It has 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 proteins in whey using capillary electrophoresis (CE) technique. The obtained measurement results provide solutions 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.

MEASURING METHOD

The method is based on preliminary preparation of the whey, its subsequent separation and quantitative determination 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.