Expandable food composition

A storage-stable composition of matter comprising:

• (i) a purified, undenatured lactoserum protein fraction obtained by extracting lactoserum first with at least one anion exchange resion and then with silica, or by extracting lactoserum first with silica and then with at least one anion exchange resin, the lactoserum being contacted with said anion exchange resin at a pH between about 4 and about 7.5 and at a temperature between about 0.degree. and about 50.degree. C., whereby protein becomes fixed to said anion exchange resin and to the silica, and then eluting the fixed protein from the anion exchange resin and from the silica, said anion exchange resin comprising a support of alumina or silica, coated with less than 20 mg/m.sup.2 of a cross-linked polymer film bearing tertiary amine functional groups or quarternary ammonium salts having the general formulae ##STR2## wherein each R, which may be identical or different, represents an alkyl or hydroxyalkyl radical having 1 to 4 carbon atoms and X is a mineral or organic anion, said silica and said support having a grain size between about 4 .mu.m and 5 mm, a specific surface of about 5 to 150 m.sup.2 /g, a pore volume of about 0.4 to 2 cm.sup.3 /g and a pore diameter between about 250 and 2500 A;
• and (ii) a Xanthomonas hydrophilic colloid;
• sufficient amounts of (i) and (ii) being present such that said composition is capable of being whipped to form a stable edible food substrate.