Mechanical load and its effect on bulb onions due to harvest and post-harvest handling

Data records of an artificial fruit (PMS-60) showed that bulb onions are subjected to a considerable number of mechanical impacts under practical harvest and postharvest handling conditions. The effect of number and intensity of impacts on onion storage losses was studied in laboratory drop tests by using hard and soft impact surfaces. After storage, the mass losses (due to transpiration and respiration losses, or rot and sprouting) were determined. The data from the artificial fruit (number of impacts, peak load and load integral of single impacts) recorded under the same drop test conditions were related to the resulting onion mass losses. In this way, allowable load thresholds for onions were derived and expressed in terms of PMS-60 data. These threshold data were used to evaluate practical handling systems by using the artificial fruit, and to predict the risk of onion storage losses based on measured impact data. (C) 1998 Silsoe Research Institute.