'Arbequina' and 'Picual' Olives in Uruguay

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Uruguay is one of the countries with favorable conditions for the development of olive tree culture. Olive oil is mainly composed by triglycerides, formed by ...
Fruit Ripening Stage Effect on the Fatty Acid Profile of ‘Arbequina’ and ‘Picual’ Olives in Uruguay A. Feippe, F. Ibáñez and G. P. Altier National Fruit Research Program National Institute for Agricultural Research Montevideo Uruguay Keywords: olive, fruit ripening, fatty acid profile, ‘Picual’, ‘Arbequina’ Abstract Uruguay is one of the countries with favorable conditions for the development of olive tree culture. Olive oil is mainly composed by triglycerides, formed by different fatty acids which confer a main portion of its properties. Its acidic composition varies mainly with variety, local climatic conditions and fruit maturity degree. The objective of this work is to know the influence of fruit maturity stages on the fatty acid profile in the ‘Arbequina’ and ‘Picual’ varieties cultivated in Uruguay. According to skin and flesh color, fruits at six stages of maturity were used for extraction of lipids and percent fatty acid composition was determined through gas chromatography on methylated byproducts, palmitic, palmitoleic, estearic, oleic, linoleic and linolenic. Across different maturity stages and on ‘Arbequina’ and ‘Picual’ the C16:0 was constant and showed a value of 20 and 19.5% respectively, showing no significant changes. The C16:1 and C18:2 significantly increased from the M1 to the M6 stage in ‘Arbequina’ and ‘Picual’ (C16:1 increased from 1.9 to 3.3 and 1.5 to 2.2 respectively; C18:2 from 8.0 to 13.3 and 1.6 to 6.5% respectively). C18:1 and of C18:3 levels significantly decreased in oils originated from fruits with more advanced maturity (C18:1 varied from 67 to 60 and 74 to 70 respectively; C18:3 varied from 0.6 to 0.4 and 0.7 to 0.5%, respectively). With advancing maturity, C18:0 level decreased in ‘Arbequina’ (1.7 to 1.4%) and increased in ‘Picual’ (1.8 to 2.5%), both showing significant variations. With advancing maturity and on both varieties, ratios between monounsaturated and polyunsaturated fatty acids decreased, and the decrease was greater in ‘Picual’. Focusing on the potential oil quality, preliminary data emphasize the importance of understanding the effect of maturity stages as related to the development of olive harvest indexes. INTRODUCTION Uruguay is located in a range of latitude of the main producing areas of olive trees. For this reason it offers natural conditions similar to the Mediterranean area, the origin of this culture. In comparison with other fruit crops, the olive culture shows a significant growth in Uruguay, because of the increase of the surface and productive volume of olives in the last years. At the moment, the main destination of the production is the elaboration of extra virgin oil. Although the commercial return is very important, its consumption has been emphasized owing to its beneficial implications for human health. Medical studies suggest that consumption of monounsaturated fats reduce the risk of cardiovascular diseases (Visioli and Galli, 2002). Others concluded that cancer rates are significantly lower among the Mediterranean population than in other places of Europe and this is related to high consumption of olive oil (Trichopoulou et al., 2000; Colomer and Menéndez, 2006). Fatty acid composition is affected by maturity of harvest fruits and variety (Nergiz and Engez, 2000; Ravetti and Matías, 2002; Conde et al., 2008). Nonetheless, it was demonstrated that the crop season is an important factor in chemical composition (Salvador et al., 2001). Irrigation practices influence monounsaturated content and polyunsaturated fatty acid (Salas et al., 1997). Others studies on olives reported that fatty Proc. 6th International Postharvest Symposium Eds.: M. Erkan and U. Aksoy Acta Hort. 877, ISHS 2010

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acid composition is influenced by the planting environment and slightly changes during the harvest period (Shibasaki, 2005; Nergiz and Engez, 2000). In order to have more information about olive crops, the objective of this work was to know the influence of fruit maturity stages on the fatty acid profile in two of the most important varieties cultivated in Uruguay. MATERIALS AND METHODS The present work was carried out on two Spanish olive varieties (‘Picual’ and ‘Arbequina’). The experimental field was installed in the Las Brujas Research Station that is located in the South of Uruguay (34°40’S;56°20’W, altitude 22 m). This place has collection of 4-year-old trees of foreign varieties planted in square and spaced 6×4 m and with three repetitions by variety. Olives were hand-picked, in optimal sanitary conditions. Fruits at six stages of maturity were used, according to skin and flesh color: M1 - green skin; M2 - yellow green skin; M3 - superficial maturity color appears; M4 - black skin and white flesh; M5 - black skin and flesh turning to purple immediately under the skin; and M6 - black skin and flesh only purple colored up the middle of fruit, and soft in texture. After harvesting, olives were quickly frozen at -80ºC until their analysis. Fruit samples at each maturity stage were crushed blended and homogenized using a blender (Ultraturrax, IKA, Staufen, Germany). For triacylglycerol (TAGs) extraction, 500 mg of homogenized olives were weighed adding 2 ml of hexane (HPLC grade). The procedure was carried out in 15 ml round-bottom Pyrex centrifuge tubes with Teflonlined screw stoppers. Extraction of TAGs was performed by an ultrasound-assisted method in an ultrasound cleaning bath (Model 3QTH-SS, Gemoro Powerful Ultrasonic, Dallas, USA) with capacity for 30 tubes. Working frequency and power were 50 kHz and 90 W, respectively. Time of extraction was 20 min and the temperature used was 25ºC at the beginning and did not exceed 30ºC. After extraction, the sample was centrifuged (10 min, 5000 rpm). The upper layer was transferred to another vial for TAGs transesterification. Fatty acid methyl esters (FAMEs) were prepared with addition of 200 μl of KOH methanolic solution (0.4 M) and shaking in a vortex for 30 s. After phase separation, the upper hexane layer was taken for gas chromatography (GC). GC of methyl esters was performed on a Shimadzu GC apparatus (Model 14 B) equipped with a flame ionization detector and capillary column HP-Innowax (30 m×0.32 mm×0.25 μm). Temperatures of injector and detector were 230 and 250ºC, respectively. The column temperature program was as follows: initial column temperature was 175ºC, which was maintained for 1 min and then increased from 175 to 230ºC at 3ºC/min, and held that way for 2 min. The amount of each sample injected was 0.4 μl. Fatty acid peaks were recorded and integrated using a N2000 Chromatography Data System (BaseLine Chromtech Research Centre, Tianjin, China). Peaks were identified based on their retention times using authentic standards of palmitic, palmitoleic, estearic, oleic, linoleic and linolenic acids methyl esters, (Sigma, USA). All samples were run in duplicate. Statistical analyses were carried out using MSTAT-C (Nissen, 1998). ANOVA analysis was used to evaluate the effect of fruit maturity on fatty acid composition and to establish differences between mean values (Tukey´s test). RESULTS AND DISCUSSION Across different maturity stages on the ‘Arbequina’ and ‘Picual’ varieties, palmitic acid was constant and showed a value of 20 and 19.5% respectively, showing no significant changes (Figs. 2 and 4). Palmitoleic and linoleic acid significantly increased from the M1 to the M6 stage in ‘Arbequina’ and ‘Picual’, and for the former acid the increase was from 1.9 to 3.3 and 1.5 to 2.2 respectively. By its side, linoleic acid showed values from 8.0 to 13.3 and 1.6 to 6.5% respectively (Figs. 1 and 3). Whereas, oleic acid and linolenic acid levels significantly decreased in oils originated from fruits with more advanced maturity. Oleic acid varied from 67 to 60 and 74 to 70 in ‘Arbequina’ and 1496

‘Picual’. Linolenic acid varied from 0.6 to 0.4 and 0.7 to 0.5%, respectively (Figs. 1, 2, 3 and 4). By its side, the estearic acid level was different in both varieties with advancing maturity. That acid decreased in ‘Arbequina’ (1.7 to 1.4%) and increased in ‘Picual’ (1.8 to 2.5%), and showed statistically significant variations for both (Figs. 1 and 3). The ratio between monounsaturated/polyunsaturated fatty acids decreased, and this decrease was greater in ‘Picual’ across M1 to M6 (Fig. 5). In ‘Arbequina’, the ratio was maintained after M3, probably due to the level of palmitoleic acid (monounsaturated) that increases at the same time as the increment in linolenic acid does (polyunsaturated). This ratio is important in nutritional properties and oxidative stability of olive oils and shows a seasonal change (Beltrán et al., 2004). CONCLUSIONS Focusing on the potential oil quality, preliminary data emphasize the importance of understanding the effect of maturity stages as related to the development of olive harvest indexes as a tool to enhance the nutritional value and stability of extra virgin olive oils. Literature Cited Beltrán, G., Del Rio, C., Sánchez, S. and Martínez, L. 2004. Influence of harvest date and crop yield on the fatty acid composition of virgin olive oil from cv. Picual. J. Agric. Food Chem. 52:3434-3440. Colomer, R. and Menéndez, J.A. 2006. Mediterranean diet, olive oil and cancer. Clin. Transl. Oncol. 8:15-21. Conde, C., Delrot, S. and Gerós, H. 2008. Physiological, biochemical and molecular changes occurring during olive development and ripening. J. Plant Phys. 165:15451562. Nergiz, C. and Engez, Y. 2000. Compositional variation of olive fruit during ripening. Food Chem. 69:55-59. Nissen, O. 1998. MSTAT-C: Microcomputer programme for the design, management, and analysis of agronomic research experiments. Vers. 1. Michigan State University, USA. Ravetti, L.M. and Matías, A.C. 2002. Characterization of virgin olive oils from Catamarca and la Rioja, Argentina. General characteristics. Acta Hort. 586:603-606. Salas, J., Pastor, M. and Vega, V. 1997. Irrigation effects on fatty acidic composition, organoleptic characteristics and other quality parameters of virgin olive oils. Grasas y aceites 48:74-82. Salvador, M.D., Aranda, F. and Fregapane, G. 2001. Influence of fruit ripening on ‘Cornicabra’ virgin olive oil quality. A study of four successive crop seasons. Food Chem. 73:45-53. Shibasaki, H. 2005. Influence of fruit ripening on chemical properties of ‘Mission’ variety olive oil in Japan. Food Sci. Technol. 11(1):9-12. Trichopoulou, A., Lagiou, P., Kuper, H. and Trichopoulou, D. 2000. Cancer and Mediterranean dietary traditions. Cancer Epidemiol. Biomarkers Prev. 9:869-873. Visioli, F. and Galli, C. 2002. Biological properties of olive oil phytochemicals. Crit. Rev. Food Sci. Nutr. 42:209-221.

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Figures

Fig. 1. Palmitoleic, estearic and linoleic acids levels in ‘Arbequina’ olive fruits at six maturity stages.

Fig. 2. Oleic, palmitic and linoleic acids level in ‘Arbequina’ olive fruits at six maturity stages.

Fig. 3. Palmitoleic, estearic, linoleic and linolenic acids levels in ‘Picual’ olive fruits at six maturity stages. 1498

Fig. 4. Oleic and palmitic acid levels in ‘Picual’ olive fruits at six maturity stages.

Fig. 5. Ratios between monounsaturated and polyunsaturated fatty acids in ‘Arbequina’ and ‘Picual’ olive fruits varieties at six maturity stages. For each variety, different letters indicate significant differences at P≤0.05 (Tukey Test).

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