Fibrosteril is a chemically inert filter aid with a complex alveolar structure which is used in continuous dosing for adsorbing those substances which are difficult to be eliminated during the normal continuous dosing filtration. The components of Fibrosteril, that is celluloses particularly treated in an acid environment and then reconstituted, and highly adsorbent bentonites without swelling properties, perform a strong adsorbent action on the deep yellow colour hues. The anthocyanins are not adsorbed.