In order to make polymers which are not only hydrophilic but also water soluble, e.g. for use to entrap yeast for bread manufacture, there can be employed copolymers of the hydroxyethyl or hydroxypropyl acrylate with 0.5 to 20% of an ammonium or alkali metal salt of an ethylenically unsaturated carboxylic acid or the strong acid salt of an ethylenically unsaturated amine.