Dynamic mechanical properties of the Russet Burbank potato as related to temperature and bruise susceptibility

An electro-mechanical vibration exciter and a dropped weight impact device were utilized to determine changes in dynamic mechanical properties of the Russet Burbank potato as influenced by temperature. The vibration exciter was utilized to study the compressive stress-strain relationship for core samples of tuberin the frequency range of 50 to 300 Hz and for temperatures from 35 to 85°F (2 to 30°C) Complex dynamic modulus, storage modulus, and phase angle were found to be independent of temperature but increased with frequency in the interval 50 to 300 Hz. Significant differences in the dynamic mechanical properties of tuber flesh were found according to location along the tuber where the samples were selected. In this study, the complex dynamic modulus was lower for the stem end than for the bud end of the tuber as was the bruise susceptibility Susceptibility of the tubers to bruise damage was evaluated by impacting the tubers with a dropped weight. Depth of bruise was found to be equivalent to length, width, area, or volume of bruise for determining bruise susceptibility. When the velocity of approach of the weight was considered, the ability to predict changes in bruise susceptibility was doubled over that of using temperature alone. This is an improtant finding because it may account for some of the unexplained variations in results of some previous studies where the impact device has been used The response of the Russet Burbank potato to impact was determined by placing a piezoelectric accelerometer in a falling weight. The acceleration-time history of the impact was recorded on a storage oscilloscope. Impact parameters were highly dependent on height of drop. Results of numerical integration of the acceleration-time curves are presented. Peak deformation was found to occur after the point of peak acceleration. Discontinuities in the acceleration-time traces were good indicators of severe damage