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 H_aSO₄ test. It was dispersed with hot 50% H₂SO₄ and the amount in the dispersion determined by the H₂SO₄-thiourea-cyste-ine-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.