This article describes the reaction between nitrite and safranine O. This sensitive reaction is based on the disappearance of color of the reddish-orange azo dye, allowing the determination of nitrite at the mg mL-1 level. A factorial optimization of parameters was carried out and the method was applied for the quantification of nitrite in sausages. The proposed experiment is attractive for the students, since several important aspects are addressed. First of all, it is not typical to explore color disappearance, especially when a chromophore such as the azoic compound safranine O is used. The quantification of nitrite is made in real samples (sausages), which are more relevant than synthetic samples. In addition, the presence of nitrite in foods leads to discussions on the function of nitrite in foodstuff and its effect on human health. The assembling of the FIA system is instructive for the students and can provide an ideal time to discuss concepts as fluid hydrodynamics, reaction kinetics, spectrophotometry, and mixing processes.