Mechanical Harvesting and Irrigation Strategy Responses on 'Arbequina
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et al., 2002) or even a reduction in Mechanical Harvesting and Irrigation Strategy the following year’s blooming (Alegre Responses on ‘Arbequina’ Olive Oil Quality et al., 2002). It is well known that irrigation modulates plant water stress and af- 1,5 2 1 Josep Rufat , Agustı J. Romero-Aroca , Amadeu Arbones , fects olive fruit ripening as well as oil Josep M. Villar3, Juan F. Hermoso2, and Miquel Pascual4 yield and quality. Hernandez et al. (2009) reported that fatty acid com- position of ‘Arbequina’ and ‘Picual’ ADDITIONAL INDEX WORDS. fatty acids, Olea europaea, sensory analysis, stability, depends on the expression of three superintensive orchard genes that are related to external SUMMARY. This study describes the effects of mechanical harvesting and irrigation on factors, including water supply. In quality in ‘Arbequina’ olive oil (Olea europaea L.). Irrigation treatments included addition, Vossen et al. (2008), work- a control, deficit irrigation (DI) during pit hardening, and subsurface deficit ing on an irrigation trial with ‘Arbe- irrigation (SDI). Results showed that mechanical harvesting damaged the olives and quina’ in California, reported an reduced olive oil quality by increasing free fatty acids (FFAs) and peroxide value, increase of PUFAs and a reduction in and by decreasing fruitiness, stability, bitterness, and pungency. DI resulted in monounsaturated fatty acids (MUFAs) increased fruit dry weight and oil content, which could be explained by their when irrigation increased, which is in reduced crop load (9.3% of crop reduction for DI and 23.9% for SDI). DI did not agreement with the results of Tovar affect olive oil characteristics, whereas SDI increased stability, fruitiness, and bitterness, and decreased polyunsaturated fatty acid (PUFAs). In conclusion, et al. (2001) who studied ‘Arbequina’ mechanical harvesting tended to damage the fruit, resulting in lower quality under different irrigation conditions olive oil, the DI strategy neither affected fruit nor olive oil characteristics, in Catalonia. However, this was not whereas the SDI strategy positively affected oil quality when greater water observed in ‘Frantoio’, which was irri- restrictions were applied. gated using a subsurface system at any of the irrigation doses used (Caruso et al., 2014). n recent years, the increasing result in a better oil quality (Camposeo Several studies suggest that olive consumption of olive oil has et al., 2013). oil composition depends on both Iboosted the planting of intensive The success of superhigh-density irrigation and the ripening process. and superintensive orchard systems to orchards relies on the availability of In this sense, total polyphenol con- achieve competitive production costs the required amount of irrigation tent is related to such factors, increas- (Arbones et al., 2014). Continuous water, which is a scarce resource in ing olive oil bitterness and oil stability mechanical harvesting is a key man- many areas. In terms of crop manage- (Motilva et al., 2000; Tovar et al., agement practice in intensive and ment, DI strategies have demonstrated 2001) as well as flavor composition superintensive groves. Some studies their feasibility for yield improvement (Caporaso, 2016). Caruso et al. (2014), have shown that this mechanical op- in arid and semiarid areas (Gomez- eration may cause internal fruit dam- analyzed the effects of irrigation on the del-Campo et al., 2014; Palese et al., lipoxygenase pathway compounds age, leading to a fast reduction of 2010). Emerging irrigation technol- quality in several varieties (Dag et al., and reported a significant increase of ı ogies such as subsurface irrigation can alcohol and ester volatiles in greater 2008; Morales-Sillero and Garc a, also optimize water efficiency by re- 2015; Yousfi et al., 2012). However, irrigation doses, suggesting a clear ef- ducing soil evaporation—a promising other researchers have reported that fect on sensory characteristics of olive water-saving strategy (Rufat et al., early harvesting and improving fruit oil, although no sensory analysis was management through mechanization 2014). Nevertheless, the optimal de- performed to confirm that possibility. gree of water restriction should be Currently, there are few pub- assessed carefully to avoid an impair- lished studies that combine the ef- This study was supported by project PET2008-0248, ment of yield and quality (Girona fect of irrigation regime and harvest Compo Expert Spain S.L., Applus Agroambiental S. A., Lab. Ferrer S.L., and Aceites Borges Pont SAU. We gratefully acknowledge the Official Tasting Panel of Virgin Olive Oils of Catalunya for the sensory Units evaluation of samples. To convert U.S. to SI, To convert SI to U.S., 1 ı Us Eficient de l’Aigua, IRTA, Parc Cient fic i Tec- multiply by U.S. unit SI unit multiply by nologic Agroalimentari de Lleida, Parc de Gardeny - Edifici Fruitcentre, E-25003 Lleida, Spain 0.4047 acre(s) ha 2.4711 2Olivicultura, Elaiotecnia i Fruita Seca, Institut de 29.5735 fl oz mL 0.0338 Recerca i Tecnologia Agroalimentaries (IRTA), Ctra. 0.3048 ft m 3.2808 Reus-El Morell, km 3.8, E-43120 Constantı, Spain 3.7854 gal L 0.2642 2.54 inch(es) cm 0.3937 3Departament de Medi Ambient i Ciencies del Sol, Universitat de Lleida, Av. Rovira Roure, 191, E-25198 25.4 inch(es) mm 0.0394 Lleida, Spain 0.4536 lb kg 2.2046 1.1209 lb/acre kgÁha–1 0.8922 4 Departament d’Hortofruticultura, Botanica i Jardineria, 0.0179 lb/inch kgÁmm–1 55.9974 Universitat de Lleida, Av. Rovira Roure, 191, E-25198 Á –1 Lleida, Spain 1 mmho/cm dS m 1 28.3495 oz g 0.0353 5 Corresponding author. E-mail: josep.rufat@irta.cat. 1 ppm mgÁkg–1 1 https://doi.org/10.21273/HORTTECH04016-18 (°F – 32) O 1.8 °F °C(°C · 1.8) + 32 • October 2018 28(5) 607 RESEARCH REPORTS method as key techniques for pro- IRRIGATION TREATMENTS. Three Methods, 1991). The results are duction and quality management of irrigation treatments were tested. The expressed as percentage of oleic acid, superintensive crop growth of olive control treatment trees were fully milliequivalents of active oxygen (O2) oil orchards in semiarid conditions. irrigated during the whole season, per kilogram oil, and specific extinc- Therefore, this work aimed to study according to the FAO methodology, tion coefficient at 232 and 270 nm the impact of several of the most based on the water balance (Allen (K232 and K270, respectively). Stabil- widespread irrigation strategies on et al., 1998). Trees under the DI ity was expressed as the oxidation ‘Arbequina’ olive oil quality, as well strategy were irrigated as the control induction time (in hours) measured as the effects caused by mechanical trees from March to June, but only according to Laubli€ and Bruttel (1986) harvesting in irrigated superintensive 25% of the dose was subsequently using the Rancimat method (model crop-growing conditions. applied to the control group during Rancimat-679; Metrohm Co., Basel, pit hardening (beginning of July until Switzerland), analyzing 2.5 g of olive Materials and methods the beginning of September), fol- oil sample at 120 °C with an air flow of E XPERIMENTAL SITE AND lowed by full irrigation from the 20 L/h. Fatty acid composition was MANAGEMENT. The trial was conducted beginning of September to the end determined by gas chromatography as on a commercial adult ‘Arbequina’ of October. The SDI strategy con- fatty acid methyl esters, according to olive plot in Torres de Segre (Lleida, sisted of applying 70% of control re- European Union Standard Methods Spain) during three consecutive years: quirements from March to June, 25% (1991). Total phenol content was 2010, 2011, and 2012. The climate is from July to the beginning of Sep- obtained using the method described a continental Mediterranean-type, with tember, and again 70% of total re- by Vazquez-Roncero et al. (1973). An an average rainfall of 350 mm/year, quirements until the end of October oil sample (10 g) was dissolved in 50 mL distributed irregularly. The trees were because of less soil evaporation. More hexane and extracted with methanol/ planted in Summer 2002 at 4.5 · details are reported in Rufat et al. water (60:40 v/v, 3 · 10 mL). The 2.2 m, resulting in a density of 1010 (2014). All plots were fertilized aqueous fractions were collected in trees/ha. The soil was moderately deep, weekly from May to October using a volumetric flask. Total phenols were calcareous with a pH of 8, and had an 50 kgÁha–1 nitrogen (N) with N-32 measured colorimetrically at 725 organic matter content of 1.5%, with solution (16% amide, 8% ammonium, nm after adding the Folin-Ciocal- a medium texture (loamy) and an elec- 8% nitrate; Compo Expert Spain, teau reagent to the extract. trical conductivity (1:5) of 2.82 dSÁm–1 Barcelona, Spain) and 100 kgÁha–1 The sensory analysis was carried (resulting from the presence of gypsum). potassium (K2O) per year. out by the Official Tasting Panel of The irrigation system consisted of auto- OLIVE OIL EXTRACTION. Fruit Virgin Olive Oils of Catalonia accord- compensated drip emitters every 60 cm were processed using an Abencor ing to European Union Standard and a water flow rate of 2.3 LÁh–1,used system (MC2; Ingenierias y Sistemas, Methods (1991). This panel relies for both surface and subsurface systems. Seville, Spain). This method repro- on ISO (International Organization Irrigation water came from the Segre duces the industrial process at a labo- for Standardization) 17025 accredita- River. Water conductivity was, on aver- ratory scale, including a metallic tion and is recognized by the Interna- age, 0.9 dSÁm–1, with chloride at 2.25 hammer mill (6-mm crusher sieve), tional Olive Oil Council. Each oil meqÁL–1, sodium at 2.14 meqÁL–1, bo- a thermo-beater at room temperature sample was analyzed by eight tasters ron less than 0.15 ppm, and nitrate less (20 °C) for 30 min, a pulp centrifuge, whoscoredtheofficial sensory descrip- than 9 ppm.