Page 155 - Analytical method for food addtives

100 Analytical methods for food additives

analysis (FIA). In-line dialysis to remove protein and remaining fat. Reduction
of nitrate to nitrite by cadmium. Reaction of nitrite with sulphanilamide and N-
(1-naphthyl)-ethylenediamine providing a red-coloured azo dye. Measuring
of the colour in a flow cell at maximum absorption of the dye at 540 nm with
reference to the absorption measured at 620 nm. Calculation of the nitrite and
nitrate contents of the sample with reference to the measured absorbances for
a series of standard solutions of nitrite and nitrate, respectively. If the nitrite
content exceeds 0.5 mg per kg, or exceeds 10 % of the nitrate content,
correction of the nitrate content by subtracting the nitrite content from the
obtained nitrate results.

A summary of the procedure for these methods and precision data are given in
Appendix 2.

9.3 Recommendations
There are numerous methods available for the analysis of nitrite in foods and the
decision as to what method should be used depends on the matrix and the analytical
instrumentation available. Methods may need to be adapted for different matrices.

9.4 References

1 Pearson’s Composition and Analysis of Foods, 9 ed. Kirk R and Sawyer R, Longman
Scientific, Harlow (1989).
2 ‘Milk and milk products – determination of nitrate and nitrite contents – Part 1: Method
using cadmium reduction and spectrometry’, BS EN International Standard ISO 14673-
1. 2001.
3 ‘AOAC Official Method 935.48. Nitrates and nitrites in meat, xylenol method’, AOAC
Official Method of Analysis (2000) 39.1.20 p 8.
4 ‘AOAC Official Method 973.31. Nitrites in cured meat, colorimetric method. Codex-
Adopted-AOAC Method’, AOAC Official Method of Analysis (2000) 39.1.21 p 8.
5 ‘AOAC Official Method 976.14. Nitrate and nitrite in cheese, modified Jones reduction
method’, AOAC Official Method of Analysis (2000) 33.7.16 p 73.
6 ‘Nitrate and nitrite content of rennet and processed cheeses’, Balcerska I, Wedzisz A,

Kopcz´nska J. Bromatologia I Chemia Toksykologiczna. (1997) 30(3), 273–276. [Polish]
7 ‘Determination of nitrites in meat systems: an improved procedure’, Binstok G, Campos
C A, Gerschenson L N. Meat Science (1996) 42(4), 401–405.
8 ‘Spectrophotometric determination of nitrate and nitrite in water and some fruit samples
using column preconcentration’, Wang G F, Satake M, Horits K. Talanta (1998) 46(4),
671–678.
9 ‘Spectrophotometric determination of nitrite after preconcentration on an SDS coated
alumun column’, Manzoori J L, Soflaee S. Analytical Letters (2001) 34(2), 231–237.
10 ‘Foodstuffs – determination of nitrate and/or nitrite content. Part 3. Spectrometric
determination of nitrate and nitrite content of meat products after enzymatic reduction
of nitrate to nitrite’, DD ENV 12014-3 : 1998, BS EN 12014-3 : 1998.
11 Validation of Enforcement Methods Service (VEMS) Method Ref 0288: Colorimetric
Method for Nitrite in Meat Products.
12 ‘Enzymatic spectrophotometric determination of nitrites in beer’, Girotti S, Ferri E N,