The Extra-Virgin Olive Oil Handbook (Peri/The Extra-Virgin Olive Oil Handbook) || Olive harvesting

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<ul><li><p>Part IIThe process</p></li><li><p>8Olive harvestingLuigi Nasini and Primo ProiettiDepartment of Agricultural, Food and Environmental Sciences, University ofPerugia, Perugia, Italy</p><p>Abstract</p><p>Monitoring of the ripening of olives in order to decide the best harvesting periodis a critical control step in extra-virgin olive oil production. The first part of thischapter presents the main phenomena of olive ripening. The second part presentsthe main harvesting systems: hand-held harvesting machines for traditional olivegroves, trunk shakers for semi-intensive and intensive olive groves and straddle har-vesters for super-intensive olive groves. Systems are compared in terms of harvest-ing efficiency and labour productivity. In Annex 8.1 a system of maturity assessmentand harvesting decision is described in detail.</p><p>8.1 Introduction</p><p>The olive harvesting operation critically influences oil yield and quality as well asthe cost of oil production. Optimizing olive harvesting entails obtaining the highestamount of oil of a predefined level of quality. In quality-oriented companies, oil yieldis a dependent variable of oil quality. In fact, the harvesting decision is determinedby the need to meet suitable sensory and analytical requirements and the yield ofolives per tree and per hectare follows as a consequence.</p><p>The influence of olive harvesting on production cost is very important (seeChapter 23). Mechanization plays a strategic role in the planning of olive grovesand in choosing the cultivars and the tree training system. Developments towards ahigh degree of harvest mechanization consist in choosing the right machinery butalso adapting the trees to machinery use.</p><p>The Extra-Virgin Olive Oil Handbook, First Edition. Edited by Claudio Peri. 2014 John Wiley &amp; Sons, Ltd. Published 2014 by John Wiley &amp; Sons, Ltd.</p></li><li><p>90 CH08 OLIVE HARVESTING</p><p>8.2 Olive ripening</p><p>The ripening process is the result of the combination of genetic, environmental andcultural conditions (Beltran et al. 2010). The most apparent changes are the increasein size of the olives and some typical change in the skin colour which, in many cases,follows a four-stage sequence (northern hemisphere):</p><p> The green stage. From August to mid-September, the olive skin is uniformlygreen.</p><p> The light-green stage. From mid-September to the first week of October,greenness progressively fades into a pale green colour.</p><p> The purple stage. From the first week of October to the last week ofNovember, significant changes in the colour of the olive take place. Thepigmentation starts to become reddish-purple often affecting only the apexof the fruit, then, with progressing maturity, extending over the entire fruitsurface, with increasingly darker tones, progressively tending to black. Thefirst part of the purple stage is often defined as veraison a word of Frenchorigin meaning the onset of ripening (invaiatura in Italian).</p><p> The black stage is when all of the skin is uniformly black and the olive can beconsidered as overripe. In the final stages of ripening, pigmentation may alsoaffect the pulp from the outermost part towards the pit.</p><p>These changes in colour, however, cannot be considered as a general rule becausethe pigmentation process is influenced by several factors, such as climate, fruit loadand, above all, the cultivar. For example, the fruit of Frantoio remains partially greenin proximity to harvest time, while those of Moraiolo turn black as harvesting timeapproaches.</p><p>In general, harvesting should be carried out at the purple stage. The first questionto be answered is: being that the purple stage is quite long (46 weeks), shouldharvesting take place at the beginning or at the end or in the middle of this period?</p><p>Secondly, it must be understood that olive ripening is a scalar process. Not all thefruits on an olive tree ripen at the same time. Ripening differs on branches that arehigh or low or on different sides of the tree. Olives in the more shaded parts of thecanopy have a lower content of total phenols and flavouring compounds. Not all thetrees in an olive grove follow the same pattern of ripening, depending on the size ofthe tree, the position in the canopy, and the fruit-load. Therefore, the descriptionof ripening given above should be considered as representing an average conditionof ripening patterns that each tree in the orchard and each fruit on a tree follows inits own way.</p><p>In the third place, the trend of the ripening process may change depending on theenvironmental conditions. The same cultivar in orchards with different exposuresor altitudes or water availability may follow a similar trend but with some shiftingof the ripening phenomena. In other words, for the same cultivar but in a different</p></li><li><p>8.3 HARVESTING SYSTEMS 91</p><p>orchard, the optimal harvesting time may change by days or weeks. The same wouldobviously be true in comparing the ripening process of the same cultivar in the sameorchard but in different years.</p><p>Some rules-of-thumb can be considered as, for example:</p><p> a hot autumn and low rainfall can cause fruit to ripen quickly, resulting in anarrow window for optimum harvesting;</p><p> a cool autumn may result in delayed ripening;</p><p> low fruit load accelerates the ripening process, whereas the opposite happenswith high fruit load;</p><p> in general, it is suitable to anticipate harvesting when: (i) the olives are underrisk of pest attack; (ii) the olives are damaged by hail; or (iii) there is a risk ofearly autumn frosts.</p><p>Monitoring of olive ripening with reliable systems is needed for deciding aboutthe best harvesting period. Annex 8.1 presents a detailed discussion of methods forassessing olive maturity and for effectively linking the maturity to the desired qualitycharacteristics of the oil.</p><p>8.3 Harvesting systems</p><p>An optimal harvesting operation can be defined as the ability to harvest more than90% of the olives on a tree in the shortest period of time and with the lowestnumber of workers with minimum mechanical damage to the olives and trees andminimum risk for workers safety and health.</p><p>The continuous evolution of harvesting systems, which has been taking place atan accelerated pace since the 1970s, is driven by the need to increase harvestingefficiency by increasing labour productivity in order to decrease harvesting cost (GilRibes et al. 2010; Tous 2012).</p><p>The harvesting operation includes olive detachment from the tree and intercep-tion/collection of the detached olives. Olive detachment from the tree is the mostcritical and costly of the harvesting operations. It can be carried out with differentsystems depending on the scale of operation and the training system of the olivetrees (Table 8.1).</p><p>8.3.1 Hand picking</p><p>Hand picking is the most expensive harvesting system due to high labour costs. Itis carried out with the aid of simple tools, for example small plastic rakes that arepulled along the fruit bearing branches. The detached fruit falls onto plastic netsspread on the ground below the crown of the olive tree; then, they are collected byhand and put into suitable crates or bins.</p></li><li><p>92 CH08 OLIVE HARVESTING</p><p>Table 8.1 The three main harvesting systems.</p><p>Harvesting systems Suitable scale of application</p><p>Hand picking and hand-heldharvesting machines</p><p>Suitable for small-scale production, any type of trainingsystem and in case of steep slopes</p><p>Trunk shakers Suitable for high-scale production in semi-intensive orintensive olive groves</p><p>Straddle harvester Suitable for high-scale production in super-intensiveolive groves</p><p>Hand picking can be used with any type of tree training system and olive grovecharacteristics (size, tree spacing, slope of the ground and so forth); it does notrequire large investment or special skills. A serious limiting condition of hand pick-ing is the high number of workers and the frequent need to use ladders, whichdecreases labour productivity and poses worker safety risks.</p><p>Under the best conditions, the productivity of hand picking is 1020 kg of olivesper hour per operator. Picking efficiency increases with increasing fruit load andwhen olive groves are on level areas, the trees are low and well pruned, so that thecrown is easily accessible to the operator.</p><p>It has been calculated that hand picking may represent about 80% of the totallabour time required for producing olives in an olive grove and 5070% of the costof the harvested olives. This is the reason why hand picking is disappearing and isbeing replaced by hand-held harvesting machines or mechanical systems.</p><p>8.3.2 Hand-held harvesting machines</p><p>Olive harvesting can be greatly facilitated by the use of harvesting machines heldand carried by the operator. Hand-held harvesting machines are available in a greatvariety of models and the design and performance is continuously being improved.The harvest labour productivity varies from 30 to 50 kg per hour per operator, butunder optimal conditions, a well-trained operator can harvest up to 150 kg per hour.The best results are obtained with medium or high weight fruit, low resistance todetachment and low and well-pruned trees, so that the crown is easily accessible tothe operating device of the harvesting machines.</p><p>Hand-held harvesting machines are suitable for all types of tree training systems,but it is important that tree height does not exceed 4 m. Therefore, it is necessarythat pruning be done to limit the growth in height and promote crown diameterdevelopment.</p><p>A hand-held harvesting machine consists of three parts: an operating device, atelescopic pole and a motor to provide the needed driving power.</p><p>The operating device</p><p>The most common operating devices are of two types: oscillating or vibrating orturning combs, and shaking hooks.</p></li><li><p>8.3 HARVESTING SYSTEMS 93</p><p>Figure 8.1 Hand-held harvesting machines: oscillating combs and the telescopic pole.</p><p>The most common operating modes of combs are:</p><p> Oscillating combs mounted on pairs and swinging against one another(Figure 8.1). The teeth may vary in number and length. The combs with longand widely spaced teeth are suitable for harvesting trees that have a densecrown (e.g. cultivars with dense foliage and/or poorly pruned trees), whilecombs with a large number of teeth are particularly useful in early harvestingof small olives with a high resistance to detachment. Combs with teeth of twosizes or a decreasing thickness from the base to the tip penetrate more easilyinto the vegetation.</p><p> Combs (beaters) with vibrating teeth on a rotating base. They have slightlylower labour productivity than oscillating combs, but cause less operatorfatigue. They are more efficient when the vegetation is not dense and inharvesting the upper parts of the crown.</p></li><li><p>94 CH08 OLIVE HARVESTING</p><p> Combs with undulated rotating teeth. The rotational movement of the teethcombines with the combing action on the crown by the operator. The labourproductivity is lower than the other combs because their area of action is morelimited. In general, they can cause greater operator fatigue because of the unbal-anced weight.</p><p>With shaking hooks, the hooks are hooked to small olive branches (5 cm diametermaximum) to which they transmit a vigorous vibration of 10001500 strokes perminute.</p><p>Shaking hooks must be equipped with antivibration systems on the handles inorder to minimize vibrations transmitted to the operator.</p><p>With combs, the fruit is detached by a beating action and by the effect of vibrationon the shoots and branches. In the case of shaking hooks the fruit is detached onlyby the effect of vibrations.</p><p>Beating may cause bruising of the fruit and therefore it should be minimized,whereas vibration is effective only if the detachment force is not too high, preferablyaround 3 N. With shaker hooks harvest can reach 9095% yield only in late harvestwith ripe fruit.</p><p>The telescopic pole</p><p>All operating devices in hand-held harvesting machines are mounted on telescopicpoles up to 24 m long made of lightweight yet durable materials, such as alu-minium, fiberglass, nylon or carbon fibre. The weight of the pole plus the combsvaries from 2 to 4 kg. In some cases the comb can be disconnected from the poleand more easily used in the lower portion of the crown. In other cases, the operatingdevices are connected to the pole by means of a swivel joint allowing the workingangle to be adjusted, depending on the characteristics and shape of the vegetation.</p><p>With the advent of telescopic poles, ladders have been abandoned, thus decreasingboth the risk to workers and working time.</p><p>The driving power</p><p>Hand-held harvesting machines are classified as pneumatic or electric. In pneumaticmachines, compressed air generated by a compressor (self-propelled or hauled by atractor) is fed through a connecting tube to the harvesting machine at a pressure of68 bars and a flow-rate of about 200 litre per minute. The use of connecting tubesof considerable length allows movement of the compressor to be minimized. It isnot advisable, however, to exceed 100 meters in length to ensure good operatingconditions. Connecting tubes can be wrapped with automatic spring wrappers,which facilitate the operation.</p><p>Electric machines are powered by batteries (12 or 24 V), connected by a cable(maximum length about 20 m). The batteries, which can also be carried by the oper-ator using an ergonomic vest, can operate for the whole day (autonomy is about7 hours of work) and then they are recharged during the night to be ready for thenext day. Electric machines have a low noise level. They are generally equipped with</p></li><li><p>8.3 HARVESTING SYSTEMS 95</p><p>a safety electronic device to prevent motor damage in case the operating teeth getblocked in the vegetation. The weight of the electric motor plus that of the pole andthe operating device is 23 kg.</p><p>Some shaking hooks are powered by a small endothermic engine (1.5 to 2.2 kW)carried by the operator by means of a harness. The endothermic engine is relativelyheavy (915 kg) and has a high noise level. The breathing of combustion gases mayalso be a further threat to workers health.</p><p>Two disadvantages of hand-held harvesting machines</p><p>In the first place, operating them may cause a relatively high level of worker fatigue,especially with heavy equipment or unbalanced distribution of the weight or intensevibrations or ergonomically inappropriate holding. In order to reduce fatigue, theharvesting teams should take turns. Periodically (about every 2 h) it is recommendedthat operators be alternated by switching between the tasks of harvesting and movingthe nets.</p><p>In the second place, hand-held harvesting machines may cause some damage tothe trees (bruising the bark and leaf fall), especially in early harvesting when it is nec-essary to dwell at length for effective fruit detachment. Bacterial and fungal growthmay affect the damaged area of the bark, so a disinfectant treatment with copperproducts immediately after harvest is recommended. Mechanical damage to the fruitis generally low if the beating action is minimized.</p><p>8.3.3 Trunk shakers</p><p>Olives are harvested by means of a vibrating grip head attached to the trunk or, in thecas...</p></li></ul>


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