Blocking agent, nitrosamine

Indeed, given an improperly designed or understood system, a blocking agent, like ascorbic acid, could be catalytic toward nitrosamine formation. For example, if the source of nitrosatlng agent is nitrite ion and the susceptible amine is in the lipid phase, conceivably ascorbic acid could cause the rapid reduction of nitrite ion to nitric oxide which could migrate to the lipid phase. Subsequent oxidation of NO to NO in the lipid phase could cause nitrosation. 

Aside from ascorbic acid and alpha-tocopherol, which have been shown to be effective blocking agents, there are other factors which appear important in blocking nitrosamine formation... 

Ascorbic acid and alpha-tocopherol are effective blocking agents against N-nitroso compound formation. Ascorbic acid is effective particularly in aqueous media, and tocopherol effective particularly in lipid phases. They should be used in conjunction due to the mutually complementary actions of the two vitamins in blocking nitrosamine formation in both aqueous and lipid media. 

In addition to vitamin C and vitamin E as effective blocking agents, there are other substances which also are capable of preventing nitrosamine formation which are present in normal foods. The influence of this factor on the design of experimental studies should not be overlooked. 

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