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Determination of denatured serum proteins in the casein fraction of heat‐treated milk by capillary zone electrophoresis
Author(s) -
Recio Isidra,
Olieman Cornelis
Publication year - 1996
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150170710
Subject(s) - capillary electrophoresis , chromatography , casein , chemistry , fraction (chemistry) , electrophoresis , capillary action , biochemistry , materials science , composite material
The amount of heat‐denatured serum proteins in heat‐treated milk could be estimated by analyzing the casein fraction, obtained by isoelectric precipitation at pH 4.6, by capillary zone electrophoresis. A hydrophilically coated capillary was used in combination with 6 M urea in a citrate buffer at pH 3. Optimization of the sample and running buffer minimized adsorption of serum proteins, especially that of bovine serum albumin (BSA). This afforded a detection limit down to ca. 5–65 μg/mL of the three main serum proteins in milk. The detector response (UV at 214 nm) was linear in the range of 0.05–0.35 and 0.05–0.85 mg/mL for α‐lactalbumin and β‐lactoglobulin, respectively. BSA showed a slightly less linear behavior, due to residual adsorption to the capillary wall. The recovery of serum proteins was in the range of 89–107%. The method was evaluated by analyzing Dutch commercial milks and cheese milk, which had received increasing heat loads. The additions of milk powder to pasteurized milk could be detected by this method as well as the serum protein to casein ratio in various products.