Microparticle-Enhanced Nephelometric Immunoassay. 2. Measurement of -Lactalbumin and ß-Lactoglobulin

¹ Laboratory of Applied Biochemistry, Associated with Institut National de la Recherche Agronomique, Faculty of Sciences, BP 239, 54506 Vandoeuvre les Nancy, France
² Laboratory of Immunology, Faculty of Medicine, BP 184, 54505 Vandoeuvre les Nancy, France
³ Sanofi Research, Montpellier, France

A microparticle-enhanced nephelometric immunoassay (NEPHELIA®) was developed for the determination of -lactalbumin and ß-lactoglobulin in bovine milk, whey, and curd from soft cheese (Camembert-type cheese) and pressed cheese (Saint Paulin-type cheese). Diluted milk, whey, and dissolved curd samples were used without pretreatment and mixed with -lactalbumin-coated or ß-lactoglobulin-coated microspheres and highly diluted anti--lactalbumin-specific or anti-ß-lactoglobulin-specific antiserum. After a reaction time of 1 h, the light scattered by the clusters of coated microspheres was measured using a nephelometer and compared with calibration curves developed with a low heat milk powder, corrected for its heat-sensitive ß-lactoglobulin content. Recovery (97.2 to 102.2%) and precision (coefficients of variation from 1.4 to 6.1% for milk and whey) studies showed the reliability of this method for the quantitation of whey proteins.

Key Words: nephelometric immunoassay • -lactalbumin • ßbeta;-lactoglobulin

Submitted on January 22, 1991
Accepted on June 19, 1991