A method of measuring the thermal diffusivity of poor conductors and its application to the heat treatment of potatoes
An apparatus and technique based on Angstrom's method is developed for measuring the thermal diffusivity of fruits and vegetables. The reproducibility of the results is found to be satisfactory with typical standard deviations of less than 6&'37. A detailed error analysis reveals that the accuracy of the technique is 7.1&'37. However, on checking the system with materials of known thermal diffusivities there was found to be a systematic error of the order of a factor of 2. A number of possible reasons for this are discussed. A method is outlined for predicting the optimum heat treatment parameters for the control of the potato disease blackleg. Some field trials were conducted which allowed the theory to be tested. During the field trials a varietal susceptibility to heat treatment was detected. The last part of the thesis concentrates on developing a means of quantifying this. Two methods were developed, the first based on the principle of increased cellular membrane permeability of damaged tissue and the second on a change in the speed of sound in damaged tissue.