Technological ripening indices for olive oil fruits Chiara Cherubini 1, Marzia Migliorini 1, Lorenzo Cecchi 1, Serena Trapani 2 and Bruno Zanoni Metropoli - Special Agency of the Chamber of Commerce of Florence - Chemical Laboratory Division; Florence –Italy 2 - Dept. Agricultural Biotechnology, University of Florence; Florence - Italy Introduction Extra virgin olive oil quality is dependent upon both olive variety, i.e. their cultivar, health conditions and degree of ripening, and operating conditions of the extraction process, i.e. time, temperature and exposure to oxygen (Migliorini et al., 2009). During ripening of olive oil fruits, biochemical processes occur, wich result in both accumulation of oil and formation of a characteristic acidic composition of olive oil (i.e. richness in oleic acid and a low polyunsaturated fatty acid content). The precursor for biosynthesis of fatty acids is acetyl-CoA, derived from catabolism of sugars such as glucose and fructose (Nergiz and Engez, 2000; Rangel et al., 1997). The sugar content has been found to decrease with time, tending to an asymptote, and the oil content has been found to follow a similar, though opposite, trend (Cherubini et al., 2009). Previous studies have also shown that olives with a high sugar content may result in defective (i.e. fusty) oil because of fermantation of sugars during the production process (Mugelli et al., 2005). Aim of the work The aim of this work was to develop technological ripening indices based on linear relationships between sugar and oil using Frantoio, Moraiolo and Leccino olive oil cultivars. Results A trend for experimental data was obtained by non-linear regression models. Experimental data were collected for the evolution of the sugar (Fig.1) and oil contents (Fig. 2) for Frantoio, Moraiolo and Leccino cultivars, respectively. The sugar content showed a decreasing sigmoidal trend tending to an asymptote for Moraiolo and Leccino cultivars, recurring for all crop seasons, while the trend for Frantoio cultivar was not always tending to an asymptote, as it resulted to be an irregular trend during 2007, 2008 and 2009 crop seasons. Figure 1. Evolution of sugar –sigmoidal model. Figure 2 shows that the trend of the oil content is always tending to an asymptote; and this asymptotic trend is recurring for every olive oil cultivar and every crop season. Figure 2. Evolution of oil content –sigmoidal model. Figure 3 shows the trend of phenolic compounds: it is a linear decreasing trend, except for the Leccino cultivar during 2011 crop season. The trend of the sugar and oil contents, including relevant correlation indices and asymptote values expressed as g/kg dm (minimum values for non-sigmoidal trends of the sugar content), is summarised in Table 1 for each olive oil cultivar and each crop season. Conclusions Based on the optimisation principle for olive oil ripening degree, i.e. maximum oil content and minimum residual sugar content, our work allowed us to obtain following results from a large number of experimental data: 1. Determining an asymptote range (i.e. minimum/maximum value) for sugar and oil contents of a given olive oil cultivar; 2. Determining linear relationships between sugar and oil; 3. Drawing suitable 3-D plots and relationships to compare new crop seasons / harvest periods and an average trend evaluated in previous years. Materials and methods Olive oil fruits (Olea europea L.) were picked by hand once a week at 8:00 a.m. from the beginning of September to the beginning of December during crop seasons (CS) for Frantoio cultivar and during crop seasons for Moraiolo and Leccino cultivars. Olives were supplied by a farm located in San Casciano Val di Pesa (Florence, Italy). Ten cultivar trees were selected as they were quantitatively representative of orchard. Olives ( g), which presented no infection or physical damage, were selected for each crop date. Olive ripening was studied by measuring water, phenolic compounds, sugar and oil contents (Cherubini et al., 2008). For data comparison, DAFB (day after full blooming) was measured during each crop season. 10th Euro Fed Lipid Congress, September 2012, Cracow Poland Figure 3. Evolution of Phenolic content –linear model. Table 1. Parameters and correlation indices for trends of sugar, oil and phenolic compounds contents The sugar and oil contents, calculated for each olive oil cultivar and each crop season (on the left in Table 2), were then linearly correlated; overall relationships were subdivided by olive oil cultivar and resulted to be statistically significant (on the right in Table 2). Table 2. Parameters and correlations for the linear relationship between the sugar and oil contents. Sugar-oil correlations were then applied as a function of DAFB to 3-D plots (x = oil content, y = sugar content, z = DAFB). The 3-D plots relating to 2010 crop season are reported as an example in Figure 3. Figure 3. 3-D plots: Frantoio, Moraiolo and Leccino cultivars from 2010 crop season. SugarOilPhenolic compounds Trend Asymptote - Min valuer2r2 Asymptoter2r2 Trendr2r2 mqmaxminVariazione % Frantoio 2011Sigmoidal69,20,734230,84Linear0,76-57, Sigmoidal46,00,884290,88Linear0,78-157, Step49,50,814550,96Linear0,81-212, Double Step60,40, ,91Linear0,85-362, Triple Step41,90,984660,89Linear0,80-307, Moraiolo 2011Sigmoidal71,30,854030,92Linear0,84-241, Sigmoidal54,60,934710,84Linear0,92-220, Sigmoidal69,20,974590,91Linear0,58-217, Leccino 2011Sigmoidal64,50,874730,93Non-Linear0, Sigmoidal50,10,864140,88Linear0,91-176, Sigmoidal103,00,933130,97Linear0,82-409, CVCSr2r2 m (slopes)q Frantoio 20110,52-3, ,53-4, ,293, ,66-4, ,06-1,54507 Moraiolo 20110,27-1, ,69-3, ,80-5,49924 Leccino 20110,58-5, ,56-2, ,49-1,92530 Totalr2r2 mq Frantoio ,44-3,10598 Moraiolo ,44-2,55623 Leccino ,67-1,93525 References Cherubini C, Migliorini M, Mugelli M, Viti P, Berti A, Cini E, Zanoni B. Towards a technological ripening index for olive oil fruit. 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