Detection of Spoiled Pork Disguised with Sodium Nitrite in Sausages Using Electrochemical Impedance Spectroscopy

Abstract

Adding Sodium Nitrite (NaNO₂) to spoiled pork to make it look fresh is a major problem for food safety. This study uses Electrochemical Impedance Spectroscopy (EIS) to quickly detect this fraud by measuring the electrical properties (10 Hz – 550 kHz) of sausages made from fresh pork and spoiled pork treated with NaNO₂. The results explain how NaNO₂ hides the spoiled meat structure. Fresh samples show a sharp drop in total impedance at high frequencies because salt breaks the cell membranes, allowing ions to flow freely. In contrast, spoiled samples treated with NaNO₂ maintain a higher impedance and show a phase angle that quickly drops to 0°. This happens because NaNO₂ creates strong links between proteins, forming a fake electrical barrier that blocks ion flow. Because the Nyquist plots for both samples look very similar, they are not reliable for practical testing. Instead, the clear differences in impedance magnitude and phase angle on the Bode plots prove that EIS can accurately distinguish naturally fresh meat from chemically hidden spoiled meat.