The preparation of a proteinaceous substance suitable for use in a foodstuff is described which comprises fungal fells of the order Mucorales. The cells are grown in a fermentor vessel in a liquid which is mixed during fermentation, after which the RNA content of the fungal cells is reduced to below 4% the fungal cells processed into an edible substance. This substance is then mechanically texturized into edible textured product for inclusion into foodstuffs, for example in the form of chunks as a meat substitute.