Nitrates and nitrites: These are added as preservatives to particularly meat products like ham, bacon and pickled meat. They are especially effective against bacteria like Clostridium botulinum and Staphylococcus aureus which have a long history of causing lethal food poisoning. Its preservative action is mainly due to the formation of nitric acid and other oxides of nitrogen and their action increases with decreasing pH value. Nitrates are more effective when they are used in combination with common salt. The presence of nitrites imparts the characteristic pink color to meat apart from protecting its flavor. It also delays the development of off-flavors during storage. Note, nitrates and nitrites are, -however, not permitted to be added to any infant food.