Improved extraction method for avoiding the interference of ascorbic acid in the spectrophotometric determination of nitrite in meat products

In minced meat products, ascorbic acid interferes in the usual spectrophotometric determination of nitrite by the diazotisation-coupling technique with sulphanilamide and N-(1-naphthyl)ethylenediamine. In a modified extraction method, the enzyme ascorbate oxidase was shown to diminish the interference of the acid. Within 10 min the enzyme was able to reduce the level of ascorbic acid in the minced meat specimens from 1000 p.p.m. down to the tolerance limit for interference. This appeared to be superior to the extraction method involving the use of water and was comparable to a previously described method based on the use of 0.01 M sodium hydroxide. As isoascorbic acid is not approved as a food additive in Norway no attempt was made to investigate the influence of this acid.