Bruising pattern of table olives (‘Manzanilla’ and ‘Hojiblanca’ cultivars) caused by hand-held machine harvesting methods

Abstract

This work presents a characterisation of the fruit and the bruising caused by some common detachment methods (manual, stick, shaker comb, branch shaker) and interception methods (net or padding) in common table olive varieties. We took pictures of fruit samples inside a special device, and the images were processed to extract characteristic parameters of shape and size (number of spots, Feret diameter, circularity, colours …). Moreover, we studied the time evolution of bruising caused on the fruit by a controlled impact. Finally, we developed a system that allows synchronised rotation of the fruit with image capture to evaluate bruising on the whole volume of the fruit. Our results showed that different harvesting treatments produced differences in the average number and diameter of spots per fruit, as well as in the average area of the spots per fruit for the different varieties. Fruit colour or bruising can also serve as a control factor for computer vision characterisation, for which reason we recorded differences in the firmness of the bruised and non-bruised areas of fruit. The harvesting method that caused the highest median values of bruise index was the shaker comb, particularly for ‘Manzanilla’ with an index of 1.59% on padding compared to 0.24% for ‘Hojiblanca’. Net interception was also observed to increase the bruise index in ‘Manzanilla’ (5.85%). Bruising assessment that only considers a single photograph means that a considerable amount of bruising remains disregarded compared to the actual bruising on the whole volume of the fruit.