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 impact sensitivity (bruise susceptibility). Russet Burbank and Atlantic cultivars of potato tuber tissue samples were loaded to failure under dynamic axial compression at 5, 10, and 15°C and 4 turgor levels corresponding to relative mass losses of 0-1.5%, 1.5-3%, 3-4.5%, and > 4.5% that resulted from air drying. Strain rate was constant at 80/s. Measurements were failure stress, failure strain, and shock wave propagation speed. Results showed that shock wave speed is an excellent measure of relative turgor within cultivar, with pronounced increases in wave speed with increased turgor. For both cultivars, increasing turgor resulted in significantly decreasing failure strain and tissue toughness, increasing secant modulus, and a slight decrease in failure stress. Turgor and temperature had very similar effects on the dynamic failure properties, suggesting that both variables alter the failure point through the same mechanism. The overall effect of temperature and turgor on failure stress, strain and toughness were very similar for both cultivars, implying that adjustments in either turgor or temperature, within these tested ranges, might have similar effects on the impact sensitivity of many potato cultivars. The effects of both temperature and turgor were large enough to affect tissue failure significantly. However, though Atlantic had consistently weaker tissue, Russet Burbank tissue strength was more sensitive to the changes in temperature and turgor. This difference implies that managing turgor and temperature to reduce bruising would be more successful with Russet Burbank.