Detection of factors influencing nitrite determination in meat

A critical assessment was made of the official Spanish method for determining nitrite content in meat, using a 2((k-p)) fold-over Plackett-Burman experiment to identify influencing factors (IF) affecting the analytical method; these factors were drawn from seven apparent critical factors (ACF): sample weight (W(S)), extraction temperature (T(E)), stirring extraction time (S(ET)), addition of Carrez I reagent (C(I-R)), addition of Carrez II reagent (C(II-R)), addition of borax reagent (B(R)) and color development time (D(CT)). In the experimental conditions assayed, the analytical method does not require protein precipitation. In addition, a negative effect of the Carrez reagent on nitrite determination was detected; it is thus proposed that this reagent be eliminated, in accordance with AOAC method 973.31. The use of borate improved nitrite extraction, but the W(S)/B(R) ratio must be adjusted to determine the best ratio and to eliminate any negative effect when the ratio increases.