Quantitative evaluation of a blueberry mechanical harvester using a miniature instrumented sphere

A key step to enhance the efficiency of the highbush blueberry production is to improve current mechanical harvesting technologies which create excessive bruising and make blueberries unmarketable to the fresh market. The overall goal of this study was to quantitatively measure the dynamic interactions between the blueberry and the mechanical harvester and to understand how bruising is created during the harvesting process. A custom-made miniature instrumented sphere, known as blueberry impact recording device (BIRD), was used to measure the mechanical impacts created by a rotary mechanical harvester (Korvan 8000, Oxbo International, Lynden, WA). A close-up, visual recording of the harvesting process was made with a hand-held digital camcorder to pinpoint critical control points that create most impacts on the harvester. Four contacting surfaces (the catch pan, conveyer belt, steel tunnel, and empty lug box) on the harvester were evaluated by the BIRD sensor with regard to the impact they created. The results showed that the catch pans of the rotary harvester accounted for over 30% of all mechanical impacts imposed on a blueberry, followed by the lug (>20%), conveyer belt (13%), and shaking rod (13%). However, the high number of impacts in the lug might be overestimated by measuring only empty lugs. Thus, the most significant reduction in bruising could be achieved through improvements of the catch pans, conveyor belts, and lugs. Harvester surface evaluation confirmed that the catch pan was the hardest surface in the mechanical harvester. This study has shed light on how to reduce blueberry bruising by improving current mechanical harvesters, which will be invaluable to enhance blueberry production efficiency in the long run.