Effect of the aggregation-state of whey protein-based ingredients on processed cheese functionality

Undenatured whey protein isolate (WPI) was incorporated (up to 2.6%) in a processed cheese model in partial replacement of casein. On heating, increasing WPI content of the processed cheese decreased meltability and dynamic rheological properties (reduced peak tan δ values) relative to the control. No significant difference in processed cheese meltability was observed between WPI, pre-heated at pH 7 and the undenatured state. Meltability was further reduced when WPI was pre-denatured at acidic pH. Co-precipitates of casein and whey protein were prepared by heating milk (90°C x 20 min) at pH 9.5, 7.5, 4.6 or 3.0 followed by isoelectric precipitation. Co-precipitates were added as replacement for acid casein in the processed cheese model. Processed cheeses prepared from co-precipitates produced from milk heated at pH 9.5 had meltability and rheological properties on heating, which were similar to the control. Co-precipitates formed from milk heated at progressively lower pH values incrementally reduced the processed cheese melting properties.