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

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Abstract
A modification of an immunological procedure previously presented in the literature is described. The modified procedure allows the determination of microgram quantities of [beta]-lactoglobulin in complex systems which contain other proteins in amounts 10,000 times greater the amount of [beta]-lactoglobulin present. The procedure consists of permitting the solution containing [beta]-lactoglobulin to diffuse into an agar layer containing antisera to [beta]-lactoglobulin at a controlled temperature. The distance of the migration is indicated by the formation of a turbid zone in the tube and is proportional to the [beta]-lactoglobulin concentration. The useful range of the method is 10-80 [mu]g of [beta]-lactoglobulin per ml. A concentration procedure is described which will allow determination of less than 1 [mu]g of [beta]-lactoglobulin per ml. Dilution of a sample to reach the useful range is the only simple preparation required for milk and other liquid milk products. The [beta]-lactoglobulin in solid materials must be first solubilized with a suitable homogenizer.