Towards a semi-mechanical harvesting platform system for harvesting blueberries with fresh-market quality

Major concerns related to harvesting blueberries for fresh market with over-the-row (OTR) harvesters are that the quality of the fruit harvested with OTR machines is generally low and ground loss is excessive. Machine-harvested blueberries have more internal bruise and usually soften rapidly in cold storage. The objective of this study was to evaluate the fruit quality and several harvest parameters of highbush blueberries ('Aurora', 'Draper'', 'Legacy', and 'Liberty') harvested by 1) hand, 2) hand-held, air-powered olive shaker and 3) mechanical OTR harvester. The powered shaker with long and short nylon tines was operated at 45 psi (310 kPa) or 65 psi (454 kPa). The fruit harvested with an air-powered shaker was collected on a net surface attached to a portable catch frame. For each plant, the weight of total detached and green/red fruit, fruit firmness, internal bruise, Brix (%), pH, and titratable acidity (TA) was determined. In addition, fruit was sampled for weight loss, firmness and internal bruise after 1 day at room temperature (RT); and after 1, 2, 3, and 4 weeks in cold storage, plus 1 day at RT. The air-powered shaker removed 3.5 to 15 times more fruit (g min^-1) than by hand. All samples lost weight (1 to 5%) in cold storage, but the difference between harvest methods was small. In all cultivars, Brix was lower and TA was higher in fruit harvested with powered shakers than by hand or OTR harvester. Fruit firmness was higher in fruit harvested by hand compared to air-powered shaker harvested method in 'Liberty', same in 'Aurora' and 'Legacy', and lower in 'Draper'. The operating pressure and tine length has little effect on fruit quality parameters, but more fruit (3× to 15×) was harvested with long tines operated at 454 kPa compared to a shaker with short tines and operated at 310 kPa. The average bruised area and percentage of fruit with ›19% bruised was less in 'Aurora' and 'Draper' than in 'Legacy' and 'Liberty'. There was a slight difference in bruising due to shaking parameters, but the bruise was less than 8% in fruit harvested by hand and with air-powered shaker compared to ›25% in 'Legacy' harvested by an OTR harvester. These results indicated a good potential for harvesting fresh-market quality blueberries using hand-held, air-powered shakers and portable fruit catch frame.