TURGOR AND TEMPERATURE EFFECTS ON DYNAMIC FAILURE PROPERTIES OF POTATO TUBER TISSUE

Both turgor and temperature affect the dynamic failure properties of potato tuber tissue and hence its impactsensitivity (bruise susceptibility). Russet Burbank and Atlantic cultivars of potato tuber tissue samples were loaded tofailure under dynamic axial compression at 5, 10, and 15C and 4 turgor levels corresponding to relative mass losses of0-1.5%, 1.5-3%, 3-4.5%, and > 4.5% that resulted from air drying. Strain rate was constant at 80/s. Measurements werefailure stress, failure strain, and shock wave propagation speed. Results showed that shock wave speed is an excellentmeasure of relative turgor within cultivar, with pronounced increases in wave speed with increased turgor. For bothcultivars, increasing turgor resulted in significantly decreasing failure strain and tissue toughness, increasing secantmodulus, and a slight decrease in failure stress. Turgor and temperature had very similar effects on the dynamic failureproperties, suggesting that both variables alter the failure point through the same mechanism. The overall effect oftemperature and turgor on failure stress, strain and toughness were very similar for both cultivars, implying thatadjustments in either turgor or temperature, within these tested ranges, might have similar effects on the impact sensitivityof many potato cultivars. The effects of both temperature and turgor were large enough to affect tissue failuresignificantly. However, though Atlantic had consistently weaker tissue, Russet Burbank tissue strength was more sensitiveto the changes in temperature and turgor. This difference implies that managing turgor and temperature to reducebruising would be more successful with Russet Burbank.