POTATO IMPACT DAMAGE THRESHOLDS

Bruise damage to potato tubers (Solanum tuberosum) appears as a result of impacts and compression. Substantial bruising in potatoes occurs d uring harvesting and handling operations, costing the average grower b etween $10,000 and $50,000 annually depending upon the year's growing and harvesting conditions, cultivar; cultural practices, and tuber con dition. This study focused on the effects of temperature and cushionin g on bruising (impact damage) thresholds of Russet Burbank potatoes. T he results provide potato tuber bruise probability reference data for use with the instrumented sphere impact evaluation device. Russet Burb ank potatoes tubers at 10 degrees 15.5 degrees and 21 degrees C were d ropped from 10 heights onto a steel surface, and onto 6.3-mm (1/4 in.) , and 13-mm (1/2 in.) thick Poron(TM) surfaces (10 tubers/treatment). Tubers at the lowest temperature were the most susceptible to damage. Cushioning the impact surface reduced the amount of bruise in all case s. As drop height increased, bruise type shifted from blackspot to sha tter bruise and cracking, implying a continuum of damage type that is dependent at least in part upon approach velocity. The drop heights wh ich bruised 10% of the tubers at 10 degrees and 15.5 degrees C were th en translated into corresponding peak acceleration (g) and velocity ch ange (Delta nu) values necessary for use in interpreting instrumented sphere data. Resulting stem-end zero-damage allowable drop heights for 250+/-50 gram Russet Burbank tubers onto a steel anvil were 25, 30, a nd 50 mm (peak accelerations of 69, 81, and 122 G), respectively for t uber temperatures of 10, 15.5, and 21 degrees C. Adding 6.3-mm thick P oron(TM) 15250 to the anvil increased allowable heights to 200, 225, a nd 250 mm (97, 110, and 122 peak G), respectively for 10, 15.5, and 21 degrees C; and adding 13-mm Poron(TM) 15500 to the anvil increased al lowable drop heights at least another 100 mm.