Determination of β-Lactoglobulin in Complex Systems by a Simple Immunological Procedure

A simple method, based on immunological procedures described originally by Oudin, has been developed to quantitate the amount of β -lactoglobulin present in complex systems. The solution containing β -lactoglobulin is allowed to diffuse into an agar layer containing antisera to the β -lactoglobulin. The distance of this migration, as measured by the formation of a turbid zone in the tube, is proportional to the β -lactoglobulin concentration. The usable range of the method is about 10–80μg/ml. Since milk contains about 2,500μg/ml of β -lactoglobulin, dilution is the only sample preparation required for milk and liquid milk products. The β -lactoglobulin in solid materials must first be solubilized in a suitable tissue homogenizer. A concentration procedure is also described with which it has been possible to determine less than 1μg/ml of β -lactoglobulin in a complex nutrient medium used to maintain bovine mammary secretory cells in laboratory culture and containing levels of other proteins up to ten-thousand times more concentrated than the β -lactoglobulin.