This paper analyzes the various design parameters of the thermal conductivity (k) probe and makes design recommendations for applications for nonfrozen food materials. The k probe is a simplified application of the line-heat source theory, but this simplification contributes to the instrument error which can be minimized by paying particular attention to the size of the k probes and materials of construction As the diameter of the k probe decreases, its accuracy increases; however small k probes are difficult to make. Therefore, it is recommended that users design their k probes using the highest acceptable error for their intended applications.