Nutritional or ingestible ink composition for ink jet printing comprising: a binder comprising at least 0.5% by weight, with respect to the total weight of the ink, of at least one zein; a solvent comprising at least 10% by weight, with respect to the total weight of the ink, of one or more nutritional or ingestible solvent(s); and at least 0.1% by weight, with respect to the total weight of the ink, of one or more nutritional or ingestible dye(s) and/or pigment(s). Dispersion of particles of at least one pigment in at least one polar solvent comprises at least one zein as dispersing agent to facilitate the dispersing of particles and stabilize the dispersion. A process for marking a substrate, in particular a foodstuff, by ink jet printing with the foregoing composition and substrate, for example eggshell, provided with such a marking.