Use of Electrodialysis to Improve the Protein Stability of Frozen Skim Milks and Milk Concentrates

Removal of calcium from skim milk by electrodialysis was logarithmically related to the extent of demineralization (log% calcium removed = 0.18% ash removed + 0.53). This removal of calcium caused a logarithmic dissociation of micellar to serum (sub‐micellar) casein (log% total casein in serum = 0.020% calcium removed + 0.70). Increases in protein stability for skim milk and concentrated skim milk were related to this dissociation of micellar casein, and the initial degree of dissociation persisted throughout frozen storage. Protein stability was > 53 wk at –8°C when 80% of the casein in unconcentrated skim milk was dissociated. Concentrated skim milk was stable for > 30 wk at –8°C when 45% of the casein was dissociated. Control samples (7–9% casein dissociated) were stable for only 4–8 wk at –8°C.