Mg2+ selectively isolates gellan gum from dairy products

Gellan gum was precipitated from the papain digest of dairy products by 5% MgSO4. The precipitate was collected by centrifugation and washed with 2.5% MgSO4 until the washings were negative to the phenol H2SO4 test. It was dispersed with hot 50% H2SO4 and the amount in the dispersion determined by the H2SO4-thiourea-cysteine.HCl reagent. Recovery from chocolate milk, yogurt, evaporated milk, ice cream, cream cheese, process cheese spread, flan and blue cheese (no oil) dressing ranged from 76-95%. Prior removal of fat and starch was unnecessary. Carrageenan, xanthan gum, alginate, pectin and other hydrocolloids did not interfere.