Improved Colorimetric Method for Determining Nitrate and Nitrite in Foods

Abstract

A method is described for determining nitrate and nitrite in cured meat products, cheeses, and vegetables. The nitrite is determined colorimetrically by diazotization of sulfanilic acid and subsequent coupling with N-(l-naphthyl)-ethylenediamine. The concentration of nitrate plus nitrite is determined similarly but after reduction of the nitrate to nitrite on a cadmium column. The difference of the 2 values is a measure of the nitrate concentration. The main improvements are replacing the Griess reagent, which contains a carcinogen, with a mixture of sulfanilic acid and N-(l-naphthyl)- ethylenediamine, providing for adjustment of pH of the sample suspension during extraction and digestion by heating, and maintaining constant pH by controlled addition of buffers and acids during color development. The method was successfully applied to the analysis of 15 samples of meat products, 23 cheeses, and 6 different vegetables. The average recovery of sodium nitrite added at levels ranging from 10 to 30 ppm was 9 5% and recovery of sodium nitrate added at levels from 30 to 400 ppm was 9 4% (corrected for cadmium column efficiency).

Nitrate and nitrite in fresh vegetables from queensland

“…Following thawing and thorough mixing, 20 g of each vegetable blend was extracted with an alkaline mixture as described by Sen and Donaldson (1978). Nitrate and nitrite in the subsequent centrifuged extracts were determined by automated colorimetry (Lyons et a1 1991).…”

A comparison of inhibition of French‐bean and soybean nitrogen fixation by nitrate, 1% oxygen or direct assimilate deprivation

“…1975). Nitrite was extracted as in Sen and Donaldson (1978) from lyophilized material ground in alkaline water (7 ml water, 1.2 ml 2% NaOH for 1 g tissue), the suspension heated 10 min at 50°C was treated with 1 ml of 0.42 M ZnSOj filtered on Whatman no. 1 paper and nitrite was measured spectrophotometrically at 540 tim, after diazotization.…”

N‐Nitrosothiazolidine and N‐Nitrosothiazolidine‐4‐Carboxylic Acid in Smoked Meats and Fish

“…A 10-g aliquot of the homogenized meats or raw bacons was analyzed for residual nitrite by the method of Sen and Donaldson (1978). (Pensabene and Fiddler, 1983a;Skrypec et al, 1985;Sen et al, 1985a) in the sense that most smoked meats contain low levels of NThZ and most smoked fish are negative for NThZ (Sen et al, 1985b).…”