The effect of heat treatment or hydrolysis on cow's milk protein distributions and antigenicities

ABSTRACT

PURPOSE: Cow's milk protein is one of the most common and strongest food allergen. We investigated the effects of heat treatment on the distribution and antigenicities of major allergens from cow's milk. We also compared the protein distribution and antigenicities among cow's milk formula and its substitutes. METHODS: We heated alpha-casen, beta-lactoglobulin (BLG), alpha-lactalbumin (ALA), and crude extract of cow's milk in 100degrees C boiling water for 1 hour. We prepared crude extracts from cow's milk formula, partially hydrolyzed milk formula (pHF) and extensively hydrolyzed milk formula (eHF). The protein compositions of all the samples were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The antigenicities were determined by IgE immunoblotting with pooled serum collected from 11 patients with milk allergy. RESULTS: After heating, no significant alteration was found in casein, and the aggregates of ALA and BLG were detected with molecular weights of about 30 and 45 kDa, respectively. The antigenicities of newly detected aggregates were increased. The new aggregates of BLG with increased antigenicities were also found in heated milk total protein. Major milk allergens were not found in pHF, and residual components with a molecular weight below 10 KDa did not show IgE-binding activity. We failed to observe the residual components and antigenicities of eHF. CONCLUSION: Changes in protein distribution and antigenicity of milk total protein induced by heat treatment may not be significantly different from those of each major allergen. The residual components of pHF could have little IgE-binding capacity, and there may be few or no antigenic components in eHF.