Rapid freshness evaluation of cow milk at different storage temperatures using in situ electrical conductivity measurement

The present study investigated the efficacy of in situ electrical conductivity measurement was evaluated to estimate the freshness of cow milk. Accordingly, the same for the refrigerated milk (5 °C) gradually increased from 0.505 to 0.610 S/m during 42 days, whereas that for the milk stored at room temperature (20 °C) promptly increased from 0.708 to 1.195 S/m during 30 days. In the empirical model, the electrical conductivity freshness index (EF_i) presented a good correlation between pH and microbial growth with the freshness parameters. In the pH analysis, the EF_i could predict the pH decline in spoiled milk with a non-linear curve. Likewise, the growth of total aerobic bacteria (TAB) at 20 °C exhibited a good correlation with EF_i (ß₂ coefficient and R² values of 9.330 and of 0.977, respectively). This study thus demonstrated the practical application of in situ electrical conductivity measurement for rapid prediction of milk freshness during storage. Industrial relevance text: In the cold change system of milk, rapid assessment of freshness has its significance for food safety. Conventional evaluation of milk freshness required the analytical equipment, trained technician, labor, and time. Electrical conductivity measurement could represent the freshness of foods associated with pH changes and microbial growth. This study proposed the potential of electrical conductivity measurement for rapid assessment of milk freshness.