Development of a Microcontrolled Instrument to Determinate Thermal Conductivity of Foods

Abstract

This work was done to develop a device of easy utilization and low cost that is able to determine the thermal conductivity of foods. It is based on the utilization of the hot wire transient method. The device has a hypodermic needle. In this needle, a wire of Nickel-Chromium (that is responsible for the probe heating) and a thermistor (used to read the temperature) were inserted. The constructive system of the device is based on the use of a Basic Stamp microcontroller which controls all the analysis-related events, like temperature readings during the time, needle heating, solving equations involving the collected temperature data and showing the analysis results through a display of liquid crystal. So, the developed equipment does not need any kind of extra device to accomplish the analysis. The developed prototype was calibrated using glycerin A. P. and related to the values of thermal conductivity of three kinds of food: ketchup, condensed milk and cream milk. The thermal conductivities of these products were determined using a renowned commercial device. The results obtained with the prototype were similar to the commercial one.