Investigation of spoilage in salmon by electrochemical impedance spectroscopy and time-domain terahertz spectroscopy
Nan Zhang, Sheng Jie Lim, Jia Min Toh, Yuefan Wei, Rusli Rusli, Lin Ke
Abstract
In this study, Spoilage of salmon was investigated using electrochemical impedance spectroscopy (EIS) and terahertz time-domain spectroscopy (TDS). Salmon tissues were continuously observed for more than 20 h, from fresh to full spoilage. The complex impedance (Z) and phase shift (θ) of the salmon samples were derived based on the EIS signal. Critical frequency changes, phase shifts, and impedance variations with time at different frequencies were extracted from the data and used as indicators of the freshness of salmon. In the THz TDS analysis, time-domain spectra were recorded in transmission and reflection modes. Four stages of fish spoilage were clearly observed in both the EIS and THz TDS spectra. Although EIS is more sensitive under the current experimental conditions, THz TDS in reflection mode provides a non-invasive and non-destructive way to monitor salmon spoilage, which is practically beneficial for the food quality control industry.