The chemistry of nitrite and ascorbate in processed meat products is complex and not fully understood yet.
Although nitrite is a natural electron acceptor and hence a potential oxidizing agent, the ability of this compound to prevent lipid oxidation in meat products is well established. Ascorbate is also involved in redox reactions; this compound is an electron donor and its oxidized form (dehydroascorbic acid) is relatively unreactive and therefore terminates the propagation of free radical reaction.
Nevertheless, ascorbate can act as pro-oxidant in the presence of metal ions.
Indeed, its ability to reduce metal ions promotes the generation of reactive oxygen species through the Fenton reaction.
Hence, it has been shown that the use of ascorbate salts in processed meats inhibits lipid oxidation but pro-oxidant effects have been reported as well .