Many meat products like ham and smoked pork chop are cured. Curing is a process to preserve meat and sausages by addition of common salt. The meat develops a typical curing taste and becomes red in color. This process is important to avoid a grey coloration and a growth of microorganisms.
But by the reaction of nitrite with amino acids, carcinogenic nitrosamines might be formed.
Therefore it is important to minimize the concentration of nitrite in meat. A constant  control of the concentration of nitrite in meat is necessary to avoid risks.
The German directive concerns approval of additives in food defines limit values for the permitted concentration of nitrite in food. For meat products a maximum quantity of 150 mg/kg is prescribed. Sterilized meat products are not allowed to exceed the maximum quantity of 100 mg/kg.

Sample preparation:
Take 5 g meat of the sample and give it into a mortar. Mince the meat and add 8 ml sodium acetate solution1) (13.6 g sodium acetate in 100 ml distilled water). Mix for 1 minute. Afterwards filter through a soft filter and press slightly to get some filtrate. Folded filter paper like MN 617 we1) is most suitable for the filtration.

Testing:
Dip the test strip into the filtrate for a few seconds. Remove the test strip and wait for 30 seconds. Compare the test field with the color scale on the tube. A red-violet coloration indicates the presence of nitrite ions.

Type

Semiquantitative test strip

Presentation

Tube of 100 test strips

Color reaction

white to red-violet

Limit of sensitivity

0-1-5-10-20-40-80 mg/l NO₂^–

Reference

91311