Transactions of the ASABE Vol. 56(4): © 2013 American Society of Agricultural and Biological Engineers ISSN 2151-0032 1 EVALUATION OF FRUIT DAMAGE CAUSED BY MECHANICAL HARVESTING OF TABLE OLIVES F. Gambella, C. Dimauro, F. Paschino ABSTRACT. Labor-saving machines that beat the branches of olive trees with sticks or canes so that the mature olives fall damage the fruit and reduce the consistency, quality, and value of the product. This study tested three different coating materials (silicone, vulcanized rubber, and natural rubber), three coating thicknesses (7, 14, and 19 mm), and three rotational speeds (2000, 3000, and 4000 rpm) for the undulating teeth of a harvesting machine in order to evaluate the damage to intact drupes. Harvesting with silicone coatings of 7 and 14 mm thickness resulted in the largest percentage of undamaged fruit (67% and 65%), followed by natural rubber (63%) and vulcanized rubber (close to 50%). Keywords. Labor-saving machines, Olive damage, Tool materials. able olives are currently harvested with large shaking or vibrating machines that operate at a well-defined vibration frequency between 12 and 24 Hz and shaking time between 5 and 20 s (Fridly et al., 1973; Ferguson, 2006; Sessiz and Ӧzcan, 2006; Amirante et al., 2007; Ferguson et al., 2010). Harvesting efficiency is initially very low, between 28% and 50%, and then improves markedly, to between 53% and 75%, with the use of abscission products (Tombesi, 1990; Pellenc, 1993; Martin, 1994; Metzdakis, 1999; Tombesi et al., 2002; Visco et al., 2004; Ferguson, 2006; Sessiz and Ӧzcan, 2006; Baryeh, 2001). The use of shaking or vibrating machines guarantees a high percentage of intact fruit, around 60% to 70%, which is higher than that obtained when the olives are shaken down by hand (50% to 60%). In the hand method, the branches are beaten with sticks or canes, causing all the mature green olives to fall off the tree. This damages much of the fruit (30% to 40%) because of the effect of the direct impact of the sticks or canes on the olives. This results in later formation of more or less extensive superficial browning and injuries at different depths. Enzymatic browning of the fruit occurs a few hours after harvest. The value of the product is reduced, and there is a loss of product consistency. In addition, the product cannot be transformed into table olives, which are sold daily in crates. To avoid a high percentage of rejected product, it is necessary that the quantity of damaged fruit be minimized and not present excessive losses. For these reasons, there has been a slowdown in the development of labor-saving machines for harvesting table olives. Hand harvesting is expensive because it involves a large number of workers and thus high labor costs, but it also ensures a high-quality product. Paschino et al. (2010) carried out a preliminary study on the use of electric handheld harvesters, equipped with titanium undulating teeth coated with silicone, and the damage produced by different working conditions during harvesting in olive groves that specialized in the production of table olives. Previous experiments in the field highlighted that contact between undulating teeth with reduced coating thickness and the fruit during table olive harvesting increased the fruit damage by nearly 60%. This is because the labor-saving machines work directly on the olive tree’s crown, and the damage is caused by the rotating or vibrating action of the harvesting tool (Paschino et al., 2010). Paschino et al. (2010) also suggested a new and more suitable interception system because the present system of gathering olives in nets and then emptying the nets into crates is inefficient, time-consuming, and expensive in terms of labor hours. The aim of this study was to evaluate the performance of the machines used for mechanized harvesting of table olives in terms of the variations in coating material type (M), coating material thickness (T), and rotational speed (V) of the undulating teeth and to assess the damage caused to the olives during harvesting. MATERIALS AND METHODS MECHANIZED HARVESTING TOOL The labor-saving harvester used for the experimental tests was an electric comb (model 105C Olivella Midi, COIMA Italy srl, Pescara, Italy) (fig. 1). The comb consisted of six tungsten undulating teeth, coated with different elastic materials and driven by an electrical power pack (12 VDC, 30 A, ISO-Tech). The harvester was mounted on a telescoping pole so that drupes could be harvested up to a maximum height of 2.9 m. The rotational Submitted for review in December 2011 as manuscript number PM 9553; approved for publication by the Power & Machinery Division of ASABE in June 2013. The authors are Filippo Gambella, Researcher, Francesco Paschino, Professor, and Corrado Dimauro, Researcher, Department of Agriculture, University of Sassari, Italy; Corresponding author: Filippo Gambella, Department of Agriculture, University of Sassari, 39 Viale Italia, 07100 Sassari, Italy; phone: +39079229281; e-mail: gambella@uniss.it. T