Passage VII

Salts containing nitrite ions (NO₂^-) are often added to meats to prevent discoloration caused by air and bacterial growth. Use of NO₂^- is controversial because studies have linked NO2- with cancer. Students performed 2 experiments to measure NO₂^- levels.

Experiment 1

Four solutions, each containing a different amount of N_aNO₂ (a salt) in H₂O were prepared. A coloring agent was added that binds with NO₂^- to form a purple compound that strongly absorbs light of a specific wavelength, and each solution was diluted to 100 mL. A blank solution was prepared in the same manner, but no N_aNO₂ was added. A colorimeter (a device that measures how much light of a selected wavelength is absorbed by a sample) was used to measure the absorbance of each solution. The absorbances were corrected by subtracting the absorbance of the blank solution from each reading (see Table 1 and Figure 1).

Experiment 2

A 100 g meat sample was ground in a blender with 50 mL of H₂O and the mixture was filtered. The blender and remaining meat were then washed with H₂O, these washings were filtered, and the liquid was added to the sample solution. The coloring agent was added and the solution was diluted to 100 mL. The procedure was repeated for several meats, and the absorbances were measured (see Table 2).