VIBRATION OF FRESH FRUITS AND VEGETABLES DURING REFRIGERATED TRUCK TRANSPORT

Fresh fruits and vegetables experience losses enroute to market that a re caused by mechanical injuries. Past studies have indicated that tra nsit vibration contributes to this loss, and may be more important tha n impacts as a source of damage. In cross-country tests of cherries, n ectarines, and pears in semi-trailers equipped with steel-spring suspe nsion systems, highest Power Spectral Density (PSD) levels were found at about 3.5 Hz. In this study, PSD is used to mean acceleration spect ral density. Other frequencies with high PSD levels were 9, 18, and 25 Hz. Similar results were found in tests with fresh tomatoes. However, in trailers equipped with an air-ride suspension and loaded with toma toes, the PSD levels were attenuated at 3.5 Hz, and were reduced at ot her frequencies. The highest PSD levels were found at the rear of the trailer, with resonance in the loaded boxes occurring at some frequenc ies. Horizontal acceleration was much less than the vertical accelerat ion. Understanding acceleration levels and frequencies that occur duri ng shipment of perishables in refrigerated trailers will help to deter mine methods that will dampen the vibration energy and reduce the pres ent losses in produce quality.