A process for oxidative biostabilization of citrus pulp, comprising the following steps: feeding an amount of fresh citrus pulp, mixing said amount of fresh pulp with an amount of partially biostabilized pulp, setting the reaction mixture in a first open-chamber reactor (3) for oxidative biostabilization in air, causing the mixture to advance along said reactor (3) guaranteeing the homogeneity thereof, blowing in air from beneath into said first reactor (3), and transferring a partial mass of the mixture from an area close to or downstream of the outlet end (6) to an area upstream of the mixer.