Magnetic resonance imaging (MRI) has been used to measure the nuclear relaxation times of the protons of water containing low concentrations (0.4mM) of the diethylenetriaminepentaaceticacid complex of manganese. Given that the manganese-binding equilibrium is dependent on the local pH, this forms the basis of a physically non-invasive method for quantitation of pH in three dimensions. The basic concepts are briefly described together with specific details of how this MRI method can be used to follow the pickling of garlic immersed in vinegar and of meatballs immersed in vinegar or a tomato sauce.