Microparticle-Enhanced Nephelometric Immunoassay. 3. Application to Milk and Dairy Products

Abstract

A microparticle-enhanced nephelometric immunoassay (NEPHELIA®) has been developed for the measurement of milk, whey, and curd proteins (αs-casein, κ-casein, α-lactalbumin, and β-lactoglobulin). This new method was applied to measure milk protein variations in a year-long study. The protein levels and their chronological evolution agree with other published data. The effects of some technological treatments on these measurements were studied: α-lactalbumin and κ-casein were not modified during freezing-thawing cycles; β-lactoglobulin and αs-casein measurements were strongly influenced by freezing; the determination of heat-processed β-lactoglobulin in the presence of κ-casein was also altered; the technological treatments applied to raw milk for pasteurization and fat standardization of milk had no influence on the proteins’ measured values. The β-lactoglobulin: α-lactalbumin ratio was determined as a good indication of heat denaturation. It was unmodified in standardized milk as well as in whey. The κ-casein level in milk was correlated with some cheese-making parameters, particularly with soft and pressed cheese yield, which could be a good predictive factor in cheese making. © 1991, American Dairy Science Association. All rights reserved.