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Cooling treatment of olive paste during the oil processing: Impact on the yield and extra virgin olive oil quality
Accepted Manuscript Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive oil quality G. Veneziani, S. Esposto, A. Taticchi, S. Urbani, R. Selvaggini, I. Di Maio, B. Sordini, M. Servili PII: DOI: Reference:
S0308-8146(16)31697-1 http://dx.doi.org/10.1016/j.foodchem.2016.10.067 FOCH 20055
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
25 July 2016 10 October 2016 16 October 2016
Please cite this article as: Veneziani, G., Esposto, S., Taticchi, A., Urbani, S., Selvaggini, R., Di Maio, I., Sordini, B., Servili, M., Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive oil quality, Food Chemistry (2016), doi: http://dx.doi.org/10.1016/j.foodchem.2016.10.067
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Title
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Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive
3
oil quality.
4 5
Authors
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Veneziani, G.,* Esposto, S., Taticchi, A., Urbani, S., Selvaggini, R., Di Maio, I., Sordini, B., Servili,
7
M.
8 9
Affiliations
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Department of Agricultural, Food and Environmental Sciences, University of Perugia, Via S.
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Costanzo, 06126 Perugia, Italy.
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Abstract
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In recent years, the temperature of processed olives in many olive-growing areas was often close to
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30 °C, due to the global warming and an early harvesting period. Consequently, the new trends in
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the extraction process have to include the opportunity to cool the olives or olive paste before
17
processing to obtain high quality EVOO. A tubular thermal exchanger was used for a rapid cooling
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treatment (CT) of olive paste after crushing. The results did not show a significant difference in the
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oil yield or any modifications in the legal parameters. The cooling process determined a significant
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improvement of phenolic compounds in all the three Italian cultivar EVOOs analyzed, whereas the
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volatile compounds showed a variability largely affected by the genetic origin of the olives with C6
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aldehydes that seem to be more stable than C6 alcohols and esters.
23 *
Corresponding author Fax: +39 075 5857916. E-mail address: [email protected] (G. Veneziani) [email protected] (S. Esposto); [email protected] (A. Taticchi); [email protected] (S. Urbani); [email protected] (R. Selvaggini); [email protected] (I. Di Maio); [email protected] (B. Sordini); [email protected] (M. Servili).
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Keywords:
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Technological innovation
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Cooling treatment
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Heat exchanger
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Olive oil quality
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Polyphenols
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Volatile compounds
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1. Introduction
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The continuous changes associated with the evolution of the olive oil sector mainly regard the
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technological innovations focusing on the oil yield and quality improvement of the product
35
(Abenoza, Benito, Saldaña, Álvarez, Raso, & Sánchez-Gimeno, 2013; Bejaoui, Beltran, Aguilera, &
36
Jimenez, 2016; Clodoveo, Durante, & La Notte, 2013; Esposto et al. 2013; Jiménez, Beltrán, &
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Uceda, 2007; Leone et al., 2015; Leone, Tamborrino, Romaniello, Zagaria, & Sabella, 2014;
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Puértolas & Martínez de Marañón, 2015; Veneziani et al., 2015). This is evaluated using specific
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markers, such as phenolic and volatile compounds related to the health and sensory properties of
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extra virgin olive oil (EVOO) (El Riachy, Priego-Capote, León, Rallo, & Luque de Castro, 2011;
41
Garrido-Delgado, Dobao-Prieto, Arce, & Valcárcel, 2015; Servili, Selvaggini, Esposto, Taticchi,
42
Montedoro, & Morozzi, 2004; Veneziani et al., 2015; Vitaglione, Savarese, Paduano, Scalfi,
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Fogliano, & Sacchi, 2015). New applications in the EVOO industry, such as ultrasound, a
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microwave assisted system, a pulsed electric field and heat exchanger, were aimed to define a
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positive impact on the working efficiency of the continuous extraction system. In several cases,
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these were associated with an increase in polyphenols and volatile compounds.
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Tubular heat exchangers applied after olive crushing were introduced into the mechanical extraction
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process of the oil thanks to their capacity to establish a rapid, continuous, thermal conditioning of
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the olive paste prior to malaxation (Esposto et al., 2013; Leone et al., 2015; Veneziani et al., 2015).
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This heating treatment can reduce malaxation times, increase the phenolic concentrations and
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modify the aromatic fractions of oils, according to the genetic origins of the olives processed
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(Veneziani et al., 2015).
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An important factor, related to the use of thermal conditioning of olive paste, regards the
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increasingly widespread need to adapt to the new agronomic practices, such as early harvesting,
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during which the oil is often extracted from olives that could reach temperatures over 30 °C during
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crushing, with a negative impact on EVOO quality.
3
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The new challenge of the olive oil sector, therefore, concerns the problem of global warming and
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the consequent rise in temperature not only in the entire Mediterranean area, but also in other olive-
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growing areas, such as South America, South Africa and Australia. High temperatures during the
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harvesting period may, therefore, determine the transformation of olives characterised by
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temperatures which are too high for EVOO to achieve adequate amounts of phenolic and volatile
62
compounds, responsible for the health and sensory properties of the product. The climatic changes,
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combined with the new trends to anticipate the olive harvesting period, lead to the need to thermally
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control the olive paste, not merely for heating, but most of all to determine a cooling treatment. The
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rapid cooling of the olive paste using a tubular heat exchanger represents an innovative technology,
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which was introduced for the first time in the mechanical extraction process of olive oil, and which
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will be essential whenever the thermal condition of pastes before the malaxation process is above
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the optimal temperature to extract a high quality EVOO. Nowadays however, there are no studies
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regarding the lowering of olive paste temperature, which could be compared to the use of cold,
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climatic chambers to store the olives (Luaces, Perez, & Sanz, 2005; 2006) or to the use of dry ice,
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both of which practices are not easily adaptable to an industrial oil transformation process.
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The use of heat exchangers to cool the olive paste will make the extraction plants more adaptable to
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different variables and changes (cultivars, new agronomic practices, degree of ripening, climatic,
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seasonal pattern, etc.) and maintain a high quality standard of EVOO.
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The aim of the study regarded the introduction of a new technological evolution in the mechanical
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extraction process of oil, based on cooling the olive paste and its impact on the oil yield, the legal
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quality parameters and the phenolic and volatile composition of EVVO.
78
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2. Materials and methods
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2.1. Chemicals.
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Hydroxytyrosol (3,4-DHPEA) and tyrosol (p-HPEA) were supplied respectively by Fluka (Milan,
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Italy) and Cabru s.a.s. (Arcore, Milan, Italy) whereas the dialdehydic forms of elenolic acid linked
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to 3,4-DHPEA and p-HPEA (3,4-DHPEA-EDA and p-HPEA-EDA), the isomer of oleuropein
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aglycon (3,4-DHPEA-EA) and lignans ((+)-1-acetoxypinoresinol and (+)-pinoresinol) were
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obtained as described by Montedoro, Servili, Baldioli, Selvaggini, Miniati, and Macchioni (1993)
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and Servili, Baldioli, Selvaggini, Macchioni, and Montedoro, (1999a). All the analytical standards
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of volatile compounds Fluka and Aldrich were purchased from Sigma-Aldrich (Milan, Italy).
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2.2. Mechanical EVOO Extraction Process.
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EVOOs were extracted from olives of the Coratina, Peranzana, and Ottobratica cultivars.
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Ottobratica olives were harvested in Calabria region (Reggio Calabria) whereas the growing area of
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Coratina and Peranzana cultivars was Apulia region, in the province of Bari and in the province of
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Foggia, respectively. The olives of all cultivars were harvested during the period between the end of
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September and the last week in October 2014, and the ripening stage of these olives, evaluated on
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the basis of the pigmentation index according to the method of Pannelli, Servili, Selvaggini,
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Baldioli, and Montedoro (1994), were similar among the cultivars used and corresponded to 0.95,
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0.90 and 0.98 for Peranzana, Coratina and Ottobratica, respectively. The olives were processed
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within 48 h after harvesting, with an average temperature of the olives before processing of
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approximately 27 °C. Approximately 150 kg of each olive cultivar was processed in triplicate, using
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an industrial plant TEM 200 system (Toscana Enologica Mori, Tavarnelle Val di Pesa, Florence,
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Italy) described by Veneziani et al. (2015). The control trials were carried out with an EVO-Line
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heat exchanger (Alfa Laval S.p.A.), placed before the malaxer (Veneziani et al., 2015) and used for
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the heating or cooling treatment of the olive paste at 25 °C or 30 °C in relation to the inlet
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temperatures of the olives. The pastes of experimental tests were instantaneously cooled, using the
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105
same heat exchanger capable of determining a flash CT at 15 °C. The heated or cooled olive pastes
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were then malaxed for 30 min at 25 °C or 30 °C and the oil was extracted by centrifugation.
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Another trial was carried out using dry ice (70 kg/ton of olives) during the crushing step only for the
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cv. Ottobratica, in order to determine a rapid cooling treatment of the olive paste at 15 °C. This also
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used dry ice (CT-DI) to control the thermal increase during this first extraction phase and the results
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were compared with the oil extracted with a cooling treatment and applied only post crushing using
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the EVO-Line heat exchanger at 25 °C of malaxation.
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2.3. EVOO analyses.
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2.3.1. Legal quality parameters.
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The free acidity, peroxide value, and the UV absorption characteristics (K232, K270 and ∆K) of oils
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were evaluated in accordance with the European Official Methods (E.U. Off. J. Eur. Communities,
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2003).
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2.3.2. Moisture content.
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The determination of pomace moisture content was performed with a drying chamber Binder ED 56
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(Binder, Tuttlingen, Germany), about 200 g of pomace was dried at 105 °C for 24 h.
123 124
2.3.3. Oil content.
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The pomace oil content was analyzed with Foss-Let 15310 (A/S N. Foss Electric Denmark), 22.5 g
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of dried pomaces were mixed (Homogenizer, A/S N. Foss Electric Denmark) with 120 mL of
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tetrachloroethylene and anhydrous sodium sulphate for 2 min, and then estimated.
128 129
2.3.4. Phenolic compounds.
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The HPLC analysis of phenolic compounds of EVOOs was carried out using Agilent Technologies
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system, model 1100 (vacuum degasser, quaternary pump, autosampler, thermostatted column
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compartment, diode array detector (DAD), fluorescence detector (FLD)) controlled by ChemStation
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(Agilent Technologies, Palo Alto, CA, USA) to evaluate the chromatographic data as described by
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Selvaggini et al. (2006). Phenolic compounds were evaluated using a Spherisorb ODS-1 250 mm ×
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4.6 mm column with a particle size of 5 µm (Waters, Milford, MA, USA). The mobile phase
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consisted of 0.2% acetic acid (pH 3.1) in water (solvent A)/ methanol (solvent B) at a flow rate of 1
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mL/min. The gradient changed as follows: 95% A for 2 min, 75% A in 8 min, 60% A in 10 min,
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50% A in 16 min, and 0% A in 14 min and was maintained for 10 min., the total running time was
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73 min. All phenolic compounds were detected by DAD at 278 nm with the only exception of
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lignans detected by FLD, activated at an excitation wavelength of 280 nm and emission at 339 nm
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(Servili, Baldioli, Selvaggini, Miniati, Macchioni, & Montedoro, 1999b).
142 143
2.3.5. Volatile compounds.
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The evaluation and quantification of volatile compounds in EVOOs were done by headspace, solid-
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phase microextraction, followed by gas chromatography-mass spectrometry (HS-SPME/GC-MS),
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according to Servili, Selvaggini, Taticchi, and Montedoro (2001) with few modifications as
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explained below. Six grams of oil with the addition of 50 µL of a standard methanolic solution,
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consisting of butanal, isobutyl acetate and 1-nonanol, were mixed for 1 min. The SPME operations,
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automated by means of the Varian CP 8410 Autoinjector (Varian, Walnut Creek, CA), were applied
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exposing the SPME fiber (a 50/30 µm, 1 cm-long, DVB/Carboxen/PDMS, Stableflex; Supelco,
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Inc., Bellefonte, PA) to the vapour phase of the sample, held at 35 °C, for 30 min. The fiber was
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then inserted into the gas chromatograph (GC) injector, set in splitless mode, using a splitless inlet
153
liner of 0.75 mm ID for thermal desorption, and left for 10 min. A Varian 4000 GC-MS equipped
154
with a 1079 split/splitless injector (Varian, Walnut Creek, CA) was used. A fused-silica capillary
155
column was employed (DB-Wax-ETR, 50 m, 0.32 mm ID, 1 µm film thickness; J&W Scientific,
7
156
Folsom, CA). The column was operated with helium at a constant flow rate of 1.7 mL/min,
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maintained by an electronic flow controller (EFC). The GC oven heating programme was
158
performed as described by Veneziani et al. (2015). The total analysis time was 80 min. The mass
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spectra and retention times of each volatile compounds were compared with the authentic reference
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compounds. The results of the peak areas were calculated on the basis of the relative calibration
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curve for each compound and expressed in µg/kg of oil (Servili et al., 2001).
162 163
2.4. Statistical Analysis.
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The statistically significant differences of data were calculated by one-way ANOVA using
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SigmaPlot software package 12.3 (Systat Software Inc., San Jose, CA, USA).
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3. Results and discussion
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The first parameter analysed to evaluate the impact of the introduction of CT of olive pastes into the
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oil extraction process was oil yield. This did not show significant modifications according to the
170
results related to the oil content of pomaces reported in Table 1. In fact, the slight variations in the
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residual pomace oil shown between the different tests cannot be attributable to the cooling treatment
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of olive paste.
173
The legal quality parameters of EVOO, such as free acidity, peroxide values, K232, K270 and ∆K,
174
were not affected by the CT of olive pastes (data not shown).
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As reported in Table 2, the rapid cooling of the olive paste at 15 °C, which determined a thermal
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reduction of approximately 12 °C for all the cultivars analysed, was able to produce a significant
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increase of phenolic concentration in the EVOOs extracted at different temperatures of malaxation
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in all three Italian cultivars studied. These results can be due to the inhibitory effect of
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polyphenoloxidase (PPO) as a result of the cooling of the pastes. In fact, the PPO shows the optimal
180
temperature of activity at approximately 50 °C, whereas it has a greatly reduced level of enzymatic
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activities at temperatures below 20 °C, as described by Taticchi, Esposto, Veneziani, Urbani,
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Selvaggini, and Servili (2013). These results confirmed what had previously been observed by
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Garcia-Rodriguez, Romero-Segura, Sanz, and Perez (2015), as regards the increase of phenolic
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concentration in EVOO obtained by a partial inhibition of PPO during crushing. However, the
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quantitative modifications of phenolic amount due to the CT application were strictly affected by
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the genetic origins of the olives. Variability ranged between the minimum increase of 2.3% for cv.
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Coratina malaxed at 30 °C and the maximum, corresponding to 61.2% for the oil of cv. Peranzana
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extracted at 25 °C of malaxation. The oils of cv. Coratina, characterised by a high concentration of
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polyphenols, showed the lowest quantitative and qualitative variability as a result of the rapid
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cooling treatment of olive paste, with a rare slight increase of over 10 mg/kg of EVOO for each
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phenolic compound. The cv. Ottobratica showed an increase, mainly due to 3,4-DHPEA-EDA, of
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12% and 7.2% of total phenols for the oil malaxed at 25 °C and 30 °C, respectively.
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More significant variations of phenolic fraction were found in CT oils of cv. Peranzana,
194
characterised by a higher concentration of 3,4-DHPEA-EDA, p-HPEA-EDA and 3,4-DHPEA-EA,
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able to guarantee increases of above 50% of the total phenols in all CT oils extracted. As reported in
196
other studies, the lignans, (+)-1-acetoxypinoresinol and (+)-pinoresinol, showed the lowest
197
variability between phenolic compounds under the different operating extraction conditions for all
198
the cultivars analysed (Selvaggini et al., 2014; Veneziani et al., 2015), even though higher
199
percentage increases were found in Ottobratica and Peranzana oils extracted at 30 °C: 12.6% and
200
25.5% of the sum of lignans, respectively. The genetic origin of olives affects the phenolic
201
concentration of fruit but, at the same time, shows an important impact on the absolute activity of
202
PPO as reported in various papers (Alagna et al., 2012; Garcia-Rodriguez, Romero-Segura, Sanz,
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Sanchez-Ortiz, & Perez, 2011; Garcia-Rodriguez, et al., 2015; Goupy, Fleuriet, Amiot, & Macheix,
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1991; Migliorini, Cecchi, Cherubini, Trapani, Cini, & Zanoni, 2012; Sciancalepore & Longone,
205
1984; Sciancalepore, 1985). The low PPO activity of cv. Coratina could explain the lower impact of
206
the CT process in the phenolic concentration of oil extracted from this cultivar, compared to the
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others (Goupy et al., 1991; Taticchi et al., 2013).
208
The CT was also studied in an attempt to control the lipoxygenase (LOX) pathway. In fact, as
209
described in other previous works (Garrido-Delgado et al., 2015; Selvaggini, Esposto, Taticchi,
210
Urbani, Veneziani, Di Maio, Sordini, & Servili, 2014; Taticchi, Esposto, & Servili, 2014), the high
211
temperatures (over 30 °C) reduce the formation of C6 aldehydes and esters responsible,
212
respectively, for fresh cut grass and fruity sensory notes, whereas they appear to increase the
213
alcohol production responsible for ripe fruitiness. The rapid, olive paste cooling showed
214
quantitative and qualitative modifications of volatile compounds of EVOOs, which appear to be
215
strongly connected to the olive cultivars and the effects on the activity level of the different
216
enzymes belonging to the LOX pathway.
217
A variation in the aldehyde concentration in the EVOOs, obtained from the cv. Coratina, was not
218
detected, whereas alcohols increased in the CT oils malaxed at 25 °C and 30 °C, compared to the
10
219
control, with an increase of 18.7% and 54.3% of the sum of saturated and unsaturated alcohols,
220
respectively. The percentage increases for both temperatures of malaxation were mainly due to a
221
rise in 1-hexanol and (E)-2-hexen-1-ol, probably due to a differentiated effect of the cooling process
222
on the thermal stability and relative activity of Coratina enzymes involved in the release of these
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volatile compounds, that could have a specific response to the rapid reduction of temperature at 15
224
°C. The generally very low concentration of esters in this cultivar was reduced in both EVOOs
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malaxed at 25 °C and 30 °C following the CT of the olive paste (Table 3). This behaviour could be
226
due to a block of the lipoxygenase pathway, characterised by a strong inhibition of alcohol
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acetyltransferase activity of cv. Coratina at a low temperature, obtained by the rapid cooling
228
conditioning of the olive paste. Insignificant differences in the aldehyde concentration was also
229
observed for the cv. Ottobratica, whereas the alcohols showed a considerable reduction at both
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temperatures tested: 46.2% and 15.4% of the sum of saturated and unsaturated alcohols,
231
respectively, for the CT oils extracted at 25 °C and 30 °C compared to the control samples. As
232
regards the concentration of esters, a significant variation was found in the CT oils, characterised by
233
an increase in the sum of esters of 36.1% for the oil extracted at 25 °C and 48.5% for the other oil
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extracted at the highest temperature of malaxation (Table 3). As regards the cv. Peranzana, the data
235
showed an overall reduction in alcohols, which was more evident for the CT oil extracted at 30 °C,
236
with a 42.6% decrease in the sum of saturated and unsaturated alcohols. A high variability was also
237
observed for esters, particularly abundant in this Apulian cultivar (Leone et al., 2015; Selvaggini et
238
al., 2014; Servili et al., 2015; Veneziani et al., 2015), with an increase of 116.6% and 33.1%,
239
respectively, for the sample obtained at the lowest and at the highest temperatures tested. The
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Peranzana oils also showed no significant modification in the sum of saturated and unsaturated
241
aldehydes compared to the control samples (Table 3). The technological innovation introduced in
242
the mechanical extraction process of the oil revealed different results of volatile composition. It
243
highlighted a large cultivar-dependency, even though the rapid cooling conditioning of olive paste
244
showed a low variability in the sum of saturated and unsaturated aldehydes of all EVOOs extracted
11
245
from the three Italian olive cultivars, with a range between -0.1% and +3.7%. The cv. Coratina
246
malaxed at 30 °C had the maximum value and the cv. Peranzana showed the minimum value, when
247
the oil was also extracted at 30 °C of malaxation. The only exception was represented by the oil
248
extracted at 25 °C from olives of cv. Ottobratica, which showed an increase of 12.9%, due to a
249
higher value of (E)-2-hexenal.
250
The experiments performed using dry ice to cool the olives directly during crushing (CT-DI) was
251
carried out to compare the impact of cooling treatment on the quality of EVOO during and post
252
crushing. Table 4 shows how the phenolic fraction of CT-DI oil maintained the same increasing
253
trend of the CT test compared to the control, and did not show significant percentage variations
254
compared to CT oil. The volatile composition of CT-DI oil showed similar changes than CT sample
255
compared to control oil (Table 5), even though the increase in the sum of saturated and unsaturated
256
aldehydes was more limited in CT-DI oil than CT oil, due to the lower amount of (E)-2-hexenal. On
257
the contrary, higher values of 1-hexanol and (E)-2-hexen-1-ol were responsible for a more limited
258
reduction in the sum of saturated and unsaturated alcohols of CT-DI oil compared to the control
259
sample.
260
The cooling treatment is a thermal conditioning widely used in the food and agro industry, but this
261
was the first time it had been applied to the mechanical extraction process of olive oil. For decades
262
the researchers have, in fact focused their technological studies on the heating of olive paste to
263
improve the oil yield and the quality of the product. Nevertheless, the rapid cooling of olive paste at
264
15 °C showed very interesting results, with a positive impact on EVOO quality, mainly related to
265
the phenolic composition. The CT determined an increase in phenolic fractions for all the cultivars
266
and at both temperatures of malaxation tested, even though the percentage increase is, however,
267
linked to the different cultivar studied. The major amounts of phenolic compounds are due to a
268
thermal inhibition of the main enzymes responsible for a process of degradation during the first
269
phase of olive oil production. Even in this experiment, the volatile composition, highlighted a
270
strictly cultivar-dependent variability (Esposto et al., 2013; Inarejos-Garcia, Fregapane, &
12
271
Desamparados Salvador, 2011; Issaoui et al., 2015; Veneziani et al., 2015;), with specific responses
272
of the enzymes of the LOX pathway of each different cultivar (Chiappetta, Benincasa, &
273
Muzzalupo, I., 2015; Padilla, Hernandez, Sanz, & Martinez-Rivas, 2009; Padilla, Martinez-Rivas,
274
Perez, & Sanz, 2012a; Padilla, Hernandez, Sanz, & Martinez-Rivas, 2012b; Patui, et al., 2010) to
275
the rapid cooling treatment of olive paste.
276
13
277
Acknowledgements
278
This study was kindly supported by Alfa Laval SpA (Tavarnelle Val di Pesa, Florence, Italy) and
279
Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR), Italy (Project CLUSTER
280
CL.A.N.−Agrifood AREA1− Nutrizione e Salute Pros.IT (CTN01_00230_413096)).
281
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457 Table 1. Evaluation of moisture and oil content of olive pomace obtained at different operative conditions.a Malaxation temperature
25 °C Control
Moisture content (%) Oil content (% d.w.)
63.9 (0.7)a 65.5 9.3 (0.5)a 10.1
Moisture content (%) Oil content (% d.w.)
63.4 (0.3)ab 61.4 12.8 (0.5)a 11.3
Moisture content (%) Oil content (% d.w.)
64.3 (0.2)ab 64.7 10.6 (0.3)a 9.8
30 °C b
CT
Control cv. Coratina (1.2)a 64.1 (0.5)a (0.2)a 9.3 (1.1)a cv. Ottobratica (1.7)a 65.0 (1.2)b (0.8)ab 12.1 (0.8)ab cv. Peranzana (0.8)a 64.3 (0.4)ab (0.4)a 10.4 (2.5)a
b
CT
63.6 (0.5)a 10.2 (1.1)a
63.3 (0.4)ab 11.0 (0.1)b 61.1 (0.6)b 11.5 (0.7)a
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-b) are not significantly different (p < 0.05). bCT = cooling treatment.; d.w. = dry weight.
458 459
22
460 Table 2. Evaluation of phenolic compounds (mg/kg) of EVOOs Control and CT extracted at different operative conditions.a Malaxation temperature
25 °C Control
30 °C b
CT
Control
b
CT
cv. Coratina 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
5.1 10.0 505.8 123.7 235.3 22.7 44.5 23.8 970.8
(0.1)a (0.2)a (1.8)a (0.5)a (0.4)a (0.01)a (0.002)ab (0.005)a (1.9)a
10.9 23.6 517.3 127.5 240.7 30.8 43.4 22.8 1016.9
(0.03)b (0.1)b (2.9)b (0.1)b (0.2)a (1.0)b (0.4)a (0.1)b (3.1)b
5.1 5.6 730.4 136.9 355.4 25.1 46.5 22.7 1327.8
(0.1)a (0.7)c (3.2)c (1.9)c (4.5)b (0.5)c (0.8)ab (0.3)b (6.0)c
7.3 7.8 741.4 138.0 368.1 27.4 47.7 21.1 1358.9
(0.2)c (0.4)d (4.2)d (1.4)c (8.0)c (0.3)d (0.6)b (0.1)c (9.2)d
(0.02)c (0.1)c (0.2)c (0.1)c (0.5)c (0.1)c (0.1)c (0.1)c (0.6)c
16.3 14.3 324.8 55.3 100.1 8.4 26.0 41.6 586.9
(0.2)d (0.2)d (8.1)d (0.9)d (1.1)d (0.1)d (0.2)d (0.5)d (8.3)d
(0.4)bc (0.1)c (4.4)c (0.2)c (1.4)c (0.04)a (0.2)ab (0.2)b (7.5)c
3.1 6.4 467.7 75.5 86.9 10.5 21.9 19.9 691.9
(0.04)c (0.1)c (8.3)d (0.6)b (1.4)d (0.2)b (3.0)b (0.3)c (9.0)d
cv. Ottobratica 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
21.5 17.1 205.0 46.3 78.0 7.3 21.5 39.5 436.2
(0.1)a (0.04)a (0.7)a (0.1)a (0.1)a (0.003)a (0.05)a (0.1)a (0.8)a
20.6 16.7 251.1 48.2 80.2 7.6 23.8 40.4 488.5
(0.03)b (0.02)b (0.6)b (0.01)b (0.1)b (0.03)b (0.1)b (0.1)b (0.6)b
23.1 13.1 297.2 50.4 94.0 9.7 23.5 36.5 547.5
cv. Peranzana 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
1.3 4.9 255.6 40.0 38.8 2.7 17.6 15.5 376.4
(0.1)a (0.2)a (1.6)a (0.2)a (0.1)a (0.04)a (0.04)a (0.007)a (1.6)a
3.8 8.8 405.6 74.5 72.6 9.7 16.8 15.2 606.9
(0.2)b (0.1)b (9.6)b (1.1)b (0.9)b (0.1)b (0.1)a (0.5)ab (9.7)b
3.6 6.5 320.2 45.4 43.8 3.7 18.5 14.8 456.5
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-d) are not significantly different (p < 0.05). bCT = cooling treatment.
461 462
23
463 Table 3. Evaluation of volatile compounds (µg/kg) of EVOOs Control and CT extracted at different operative conditions.a Malaxation temperature
25 °C Control
30 °C b
CT
Control
b
CT
cv. Coratina Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate
Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate
132 1228 153429 2139 1327 1019 938 2492 890 2760
(1)a 103 (11)b (7)a 1229 (57)a (3211)ab 156300 (283)a (149)a 2049 (2)a (123)ab 1318 (7)a (50)a (35)ab (30)a (3)a (100)a
143 (6)a 71 (6)a 100 687 100237 1532 959 528 434 5190 1893 5995
(3)a (1)a (858)a (32)a (7)a (14)a (14)a (10)a (5)a (69)a
94 (1)a 210 (1)a 218 1433 138950 2613 1632 786 766 1023 1005 1678
(3)a (6)ab (7990)a (168)a (170)a (4)a (1)a (34)a (11)a (49)a
952 (13)a 1083 (37)a
883 835 3858 876 3160
(54)b (9)a (100)b (2)a (6)b
132 1297 148179 2428 1497 1056 1023 1075 824 2810
(3)a 109 (3)b (8)ab 1351 (38)b (2000)b 154000 (3960)ab (25)b 1955 (36)a (34)b 1285 (26)a (29)a (12)b (33)c (13)b (33)a
79 (2)b 97 (8)c 36 (3)b 72 (1)a cv. Ottobratica 106 650 113545 1609 1016 536 425 1978 1534 3076
(1)b (9)b (716)b (1)b (2)b (4)a (6)a (21)b (4)b (21)b
106 572 104685 1603 1011 557 446 3762 2247 4590
(1)b (4)c (746)c (26)b (9)b (21)a (13)a (53)c (60)c (33)c
132 (4)b 128 (1)b 282 (10)b 305 (26)b cv. Peranzana 217 1439 141265 2575 1765 779 864 1135 1060 1375
(5)a (81)ab (498)a (22)ab (6)a (11)a (26)b (8)b (18)b (39)b
2616 (131)b 1793 (106)b
219 1371 115443 2791 1700 832 790 2082 1170 2981
965 873 4633 434 3570
(18)c (2)a (88)d (14)c (64)c
41 (4)d 28 (2)b 99 741 105013 1595 1001 531 423 2856 1749 4258
(1)a (5)d (446)c (22)ab (26)b (8)a (6)a (20)d (32)d (42)d
197 (6)c 446 (13)c
(6)a 138 (2)b (10)b 1536 (81)b (7414)b 116060 (503)b (36)a 2348 (61)b (65)a 1357 (32)b (29)b (12)c (4)c (1)c (33)c
1132 (40)a 1294 (42)c
762 780 1579 753 1785
(4)a (4)d (17)d (16)d (2)d
1856 (81)c 1372 (74)c
24
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-d) are not significantly different (p < 0.05). b CT = cooling treatment.
464 465
25
466 Table 4. Evaluation of phenolic compounds (mg/kg) of EVOOs Control, CT and CT-DI of cv. Ottobratica malaxed at 25 °C.a Control 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
20.9 17.8 199.7 47.8 76.7 7.6 22.1 39.7 432.3
(0.2)a (0.05)a (1.8)a (0.2)a (1.1)a (0.09)a (0.2)a (1.1)a (2.4)a
b
22.8 18.6 244.1 48.1 84.2 7.8 22.9 42.2 490.7
CT (0.1)b (0.2)b (2.5)b (0.9)a (1.0)a (0.1)a (0.9)ab (1.4)a (3.3)b
c
CT-DI
26.9 19.9 228.3 47.2 95.9 7.7 24.7 43.4 494.1
(0.3)c (0.4)c (4.4)c (2.4)a (4.8)b (0.4)a (1.2)b (2.2)a (7.4)b
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-c) are not significantly different (p < 0.05). bCT = cooling treatment; cCT-DI = cooling tretment - dry ice.
467
26
468 Table 5. Evaluation of volatile composition (µg/kg) of EVOOs Control, CT and CT-DI of cv. Ottobratica malaxed at 25 °C.a Control (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Hexyl acetate (Z)-3-Hexenyl acetate
98 674 100577 1499 964 532 429 5063 1854 5979
(5)a (3)a (1222)a (19)a (32)a (22)a (9)a (28)a (9)a (84)a
89 (3)a 207 (2)a
b
CT Aldehydes 110 (1)b 668 (5)a 109890 (2455)b 1555 (1)b 975 (25)a Alcohols 529 (17)a 439 (12)a 2058 (34)b 1462 (9)b 2897 (63)b Esters 119 (7)b 269 (3)b
c
CT-DI
90 693 106111 1919 925 537 397 2924 1398 4563
(1)c (1)b (3377)ab (6)c (50)a (6)a (14)b (12)c (1)c (52)c
129 (1)c 244 (2)c
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-c) are not significantly different (p < 0.05). bCT = cooling treatment; cCT-DI = cooling tretment - dry ice.
469 470
27
471
Highlights
472 473
Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive
474
oil quality.
475 476 477 478 479 480 481 482 483 484 485
• A technological innovation is introduced in mechanical extraction process of olive oil. • For the first time the olive paste is undergone to a cooling treatment (CT) after the crushing phase. • The rapid cooling conditioning of olive paste has a positive impact on extra virgin olive oil quality. • The CT improves the phenolic concentration and modifies the volatile fraction of olive oil.
28
S0308-8146(16)31697-1 http://dx.doi.org/10.1016/j.foodchem.2016.10.067 FOCH 20055
To appear in:
Food Chemistry
Received Date: Revised Date: Accepted Date:
25 July 2016 10 October 2016 16 October 2016
Please cite this article as: Veneziani, G., Esposto, S., Taticchi, A., Urbani, S., Selvaggini, R., Di Maio, I., Sordini, B., Servili, M., Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive oil quality, Food Chemistry (2016), doi: http://dx.doi.org/10.1016/j.foodchem.2016.10.067
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1
Title
2
Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive
3
oil quality.
4 5
Authors
6
Veneziani, G.,* Esposto, S., Taticchi, A., Urbani, S., Selvaggini, R., Di Maio, I., Sordini, B., Servili,
7
M.
8 9
Affiliations
10
Department of Agricultural, Food and Environmental Sciences, University of Perugia, Via S.
11
Costanzo, 06126 Perugia, Italy.
12 13
Abstract
14
In recent years, the temperature of processed olives in many olive-growing areas was often close to
15
30 °C, due to the global warming and an early harvesting period. Consequently, the new trends in
16
the extraction process have to include the opportunity to cool the olives or olive paste before
17
processing to obtain high quality EVOO. A tubular thermal exchanger was used for a rapid cooling
18
treatment (CT) of olive paste after crushing. The results did not show a significant difference in the
19
oil yield or any modifications in the legal parameters. The cooling process determined a significant
20
improvement of phenolic compounds in all the three Italian cultivar EVOOs analyzed, whereas the
21
volatile compounds showed a variability largely affected by the genetic origin of the olives with C6
22
aldehydes that seem to be more stable than C6 alcohols and esters.
23 *
Corresponding author Fax: +39 075 5857916. E-mail address: [email protected] (G. Veneziani) [email protected] (S. Esposto); [email protected] (A. Taticchi); [email protected] (S. Urbani); [email protected] (R. Selvaggini); [email protected] (I. Di Maio); [email protected] (B. Sordini); [email protected] (M. Servili).
1
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Keywords:
25
Technological innovation
26
Cooling treatment
27
Heat exchanger
28
Olive oil quality
29
Polyphenols
30
Volatile compounds
31
2
32
1. Introduction
33
The continuous changes associated with the evolution of the olive oil sector mainly regard the
34
technological innovations focusing on the oil yield and quality improvement of the product
35
(Abenoza, Benito, Saldaña, Álvarez, Raso, & Sánchez-Gimeno, 2013; Bejaoui, Beltran, Aguilera, &
36
Jimenez, 2016; Clodoveo, Durante, & La Notte, 2013; Esposto et al. 2013; Jiménez, Beltrán, &
37
Uceda, 2007; Leone et al., 2015; Leone, Tamborrino, Romaniello, Zagaria, & Sabella, 2014;
38
Puértolas & Martínez de Marañón, 2015; Veneziani et al., 2015). This is evaluated using specific
39
markers, such as phenolic and volatile compounds related to the health and sensory properties of
40
extra virgin olive oil (EVOO) (El Riachy, Priego-Capote, León, Rallo, & Luque de Castro, 2011;
41
Garrido-Delgado, Dobao-Prieto, Arce, & Valcárcel, 2015; Servili, Selvaggini, Esposto, Taticchi,
42
Montedoro, & Morozzi, 2004; Veneziani et al., 2015; Vitaglione, Savarese, Paduano, Scalfi,
43
Fogliano, & Sacchi, 2015). New applications in the EVOO industry, such as ultrasound, a
44
microwave assisted system, a pulsed electric field and heat exchanger, were aimed to define a
45
positive impact on the working efficiency of the continuous extraction system. In several cases,
46
these were associated with an increase in polyphenols and volatile compounds.
47
Tubular heat exchangers applied after olive crushing were introduced into the mechanical extraction
48
process of the oil thanks to their capacity to establish a rapid, continuous, thermal conditioning of
49
the olive paste prior to malaxation (Esposto et al., 2013; Leone et al., 2015; Veneziani et al., 2015).
50
This heating treatment can reduce malaxation times, increase the phenolic concentrations and
51
modify the aromatic fractions of oils, according to the genetic origins of the olives processed
52
(Veneziani et al., 2015).
53
An important factor, related to the use of thermal conditioning of olive paste, regards the
54
increasingly widespread need to adapt to the new agronomic practices, such as early harvesting,
55
during which the oil is often extracted from olives that could reach temperatures over 30 °C during
56
crushing, with a negative impact on EVOO quality.
3
57
The new challenge of the olive oil sector, therefore, concerns the problem of global warming and
58
the consequent rise in temperature not only in the entire Mediterranean area, but also in other olive-
59
growing areas, such as South America, South Africa and Australia. High temperatures during the
60
harvesting period may, therefore, determine the transformation of olives characterised by
61
temperatures which are too high for EVOO to achieve adequate amounts of phenolic and volatile
62
compounds, responsible for the health and sensory properties of the product. The climatic changes,
63
combined with the new trends to anticipate the olive harvesting period, lead to the need to thermally
64
control the olive paste, not merely for heating, but most of all to determine a cooling treatment. The
65
rapid cooling of the olive paste using a tubular heat exchanger represents an innovative technology,
66
which was introduced for the first time in the mechanical extraction process of olive oil, and which
67
will be essential whenever the thermal condition of pastes before the malaxation process is above
68
the optimal temperature to extract a high quality EVOO. Nowadays however, there are no studies
69
regarding the lowering of olive paste temperature, which could be compared to the use of cold,
70
climatic chambers to store the olives (Luaces, Perez, & Sanz, 2005; 2006) or to the use of dry ice,
71
both of which practices are not easily adaptable to an industrial oil transformation process.
72
The use of heat exchangers to cool the olive paste will make the extraction plants more adaptable to
73
different variables and changes (cultivars, new agronomic practices, degree of ripening, climatic,
74
seasonal pattern, etc.) and maintain a high quality standard of EVOO.
75
The aim of the study regarded the introduction of a new technological evolution in the mechanical
76
extraction process of oil, based on cooling the olive paste and its impact on the oil yield, the legal
77
quality parameters and the phenolic and volatile composition of EVVO.
78
4
79
2. Materials and methods
80
2.1. Chemicals.
81
Hydroxytyrosol (3,4-DHPEA) and tyrosol (p-HPEA) were supplied respectively by Fluka (Milan,
82
Italy) and Cabru s.a.s. (Arcore, Milan, Italy) whereas the dialdehydic forms of elenolic acid linked
83
to 3,4-DHPEA and p-HPEA (3,4-DHPEA-EDA and p-HPEA-EDA), the isomer of oleuropein
84
aglycon (3,4-DHPEA-EA) and lignans ((+)-1-acetoxypinoresinol and (+)-pinoresinol) were
85
obtained as described by Montedoro, Servili, Baldioli, Selvaggini, Miniati, and Macchioni (1993)
86
and Servili, Baldioli, Selvaggini, Macchioni, and Montedoro, (1999a). All the analytical standards
87
of volatile compounds Fluka and Aldrich were purchased from Sigma-Aldrich (Milan, Italy).
88 89
2.2. Mechanical EVOO Extraction Process.
90
EVOOs were extracted from olives of the Coratina, Peranzana, and Ottobratica cultivars.
91
Ottobratica olives were harvested in Calabria region (Reggio Calabria) whereas the growing area of
92
Coratina and Peranzana cultivars was Apulia region, in the province of Bari and in the province of
93
Foggia, respectively. The olives of all cultivars were harvested during the period between the end of
94
September and the last week in October 2014, and the ripening stage of these olives, evaluated on
95
the basis of the pigmentation index according to the method of Pannelli, Servili, Selvaggini,
96
Baldioli, and Montedoro (1994), were similar among the cultivars used and corresponded to 0.95,
97
0.90 and 0.98 for Peranzana, Coratina and Ottobratica, respectively. The olives were processed
98
within 48 h after harvesting, with an average temperature of the olives before processing of
99
approximately 27 °C. Approximately 150 kg of each olive cultivar was processed in triplicate, using
100
an industrial plant TEM 200 system (Toscana Enologica Mori, Tavarnelle Val di Pesa, Florence,
101
Italy) described by Veneziani et al. (2015). The control trials were carried out with an EVO-Line
102
heat exchanger (Alfa Laval S.p.A.), placed before the malaxer (Veneziani et al., 2015) and used for
103
the heating or cooling treatment of the olive paste at 25 °C or 30 °C in relation to the inlet
104
temperatures of the olives. The pastes of experimental tests were instantaneously cooled, using the
5
105
same heat exchanger capable of determining a flash CT at 15 °C. The heated or cooled olive pastes
106
were then malaxed for 30 min at 25 °C or 30 °C and the oil was extracted by centrifugation.
107
Another trial was carried out using dry ice (70 kg/ton of olives) during the crushing step only for the
108
cv. Ottobratica, in order to determine a rapid cooling treatment of the olive paste at 15 °C. This also
109
used dry ice (CT-DI) to control the thermal increase during this first extraction phase and the results
110
were compared with the oil extracted with a cooling treatment and applied only post crushing using
111
the EVO-Line heat exchanger at 25 °C of malaxation.
112 113
2.3. EVOO analyses.
114 115
2.3.1. Legal quality parameters.
116
The free acidity, peroxide value, and the UV absorption characteristics (K232, K270 and ∆K) of oils
117
were evaluated in accordance with the European Official Methods (E.U. Off. J. Eur. Communities,
118
2003).
119 120
2.3.2. Moisture content.
121
The determination of pomace moisture content was performed with a drying chamber Binder ED 56
122
(Binder, Tuttlingen, Germany), about 200 g of pomace was dried at 105 °C for 24 h.
123 124
2.3.3. Oil content.
125
The pomace oil content was analyzed with Foss-Let 15310 (A/S N. Foss Electric Denmark), 22.5 g
126
of dried pomaces were mixed (Homogenizer, A/S N. Foss Electric Denmark) with 120 mL of
127
tetrachloroethylene and anhydrous sodium sulphate for 2 min, and then estimated.
128 129
2.3.4. Phenolic compounds.
6
130
The HPLC analysis of phenolic compounds of EVOOs was carried out using Agilent Technologies
131
system, model 1100 (vacuum degasser, quaternary pump, autosampler, thermostatted column
132
compartment, diode array detector (DAD), fluorescence detector (FLD)) controlled by ChemStation
133
(Agilent Technologies, Palo Alto, CA, USA) to evaluate the chromatographic data as described by
134
Selvaggini et al. (2006). Phenolic compounds were evaluated using a Spherisorb ODS-1 250 mm ×
135
4.6 mm column with a particle size of 5 µm (Waters, Milford, MA, USA). The mobile phase
136
consisted of 0.2% acetic acid (pH 3.1) in water (solvent A)/ methanol (solvent B) at a flow rate of 1
137
mL/min. The gradient changed as follows: 95% A for 2 min, 75% A in 8 min, 60% A in 10 min,
138
50% A in 16 min, and 0% A in 14 min and was maintained for 10 min., the total running time was
139
73 min. All phenolic compounds were detected by DAD at 278 nm with the only exception of
140
lignans detected by FLD, activated at an excitation wavelength of 280 nm and emission at 339 nm
141
(Servili, Baldioli, Selvaggini, Miniati, Macchioni, & Montedoro, 1999b).
142 143
2.3.5. Volatile compounds.
144
The evaluation and quantification of volatile compounds in EVOOs were done by headspace, solid-
145
phase microextraction, followed by gas chromatography-mass spectrometry (HS-SPME/GC-MS),
146
according to Servili, Selvaggini, Taticchi, and Montedoro (2001) with few modifications as
147
explained below. Six grams of oil with the addition of 50 µL of a standard methanolic solution,
148
consisting of butanal, isobutyl acetate and 1-nonanol, were mixed for 1 min. The SPME operations,
149
automated by means of the Varian CP 8410 Autoinjector (Varian, Walnut Creek, CA), were applied
150
exposing the SPME fiber (a 50/30 µm, 1 cm-long, DVB/Carboxen/PDMS, Stableflex; Supelco,
151
Inc., Bellefonte, PA) to the vapour phase of the sample, held at 35 °C, for 30 min. The fiber was
152
then inserted into the gas chromatograph (GC) injector, set in splitless mode, using a splitless inlet
153
liner of 0.75 mm ID for thermal desorption, and left for 10 min. A Varian 4000 GC-MS equipped
154
with a 1079 split/splitless injector (Varian, Walnut Creek, CA) was used. A fused-silica capillary
155
column was employed (DB-Wax-ETR, 50 m, 0.32 mm ID, 1 µm film thickness; J&W Scientific,
7
156
Folsom, CA). The column was operated with helium at a constant flow rate of 1.7 mL/min,
157
maintained by an electronic flow controller (EFC). The GC oven heating programme was
158
performed as described by Veneziani et al. (2015). The total analysis time was 80 min. The mass
159
spectra and retention times of each volatile compounds were compared with the authentic reference
160
compounds. The results of the peak areas were calculated on the basis of the relative calibration
161
curve for each compound and expressed in µg/kg of oil (Servili et al., 2001).
162 163
2.4. Statistical Analysis.
164
The statistically significant differences of data were calculated by one-way ANOVA using
165
SigmaPlot software package 12.3 (Systat Software Inc., San Jose, CA, USA).
166
8
167
3. Results and discussion
168
The first parameter analysed to evaluate the impact of the introduction of CT of olive pastes into the
169
oil extraction process was oil yield. This did not show significant modifications according to the
170
results related to the oil content of pomaces reported in Table 1. In fact, the slight variations in the
171
residual pomace oil shown between the different tests cannot be attributable to the cooling treatment
172
of olive paste.
173
The legal quality parameters of EVOO, such as free acidity, peroxide values, K232, K270 and ∆K,
174
were not affected by the CT of olive pastes (data not shown).
175
As reported in Table 2, the rapid cooling of the olive paste at 15 °C, which determined a thermal
176
reduction of approximately 12 °C for all the cultivars analysed, was able to produce a significant
177
increase of phenolic concentration in the EVOOs extracted at different temperatures of malaxation
178
in all three Italian cultivars studied. These results can be due to the inhibitory effect of
179
polyphenoloxidase (PPO) as a result of the cooling of the pastes. In fact, the PPO shows the optimal
180
temperature of activity at approximately 50 °C, whereas it has a greatly reduced level of enzymatic
181
activities at temperatures below 20 °C, as described by Taticchi, Esposto, Veneziani, Urbani,
182
Selvaggini, and Servili (2013). These results confirmed what had previously been observed by
183
Garcia-Rodriguez, Romero-Segura, Sanz, and Perez (2015), as regards the increase of phenolic
184
concentration in EVOO obtained by a partial inhibition of PPO during crushing. However, the
185
quantitative modifications of phenolic amount due to the CT application were strictly affected by
186
the genetic origins of the olives. Variability ranged between the minimum increase of 2.3% for cv.
187
Coratina malaxed at 30 °C and the maximum, corresponding to 61.2% for the oil of cv. Peranzana
188
extracted at 25 °C of malaxation. The oils of cv. Coratina, characterised by a high concentration of
189
polyphenols, showed the lowest quantitative and qualitative variability as a result of the rapid
190
cooling treatment of olive paste, with a rare slight increase of over 10 mg/kg of EVOO for each
191
phenolic compound. The cv. Ottobratica showed an increase, mainly due to 3,4-DHPEA-EDA, of
192
12% and 7.2% of total phenols for the oil malaxed at 25 °C and 30 °C, respectively.
9
193
More significant variations of phenolic fraction were found in CT oils of cv. Peranzana,
194
characterised by a higher concentration of 3,4-DHPEA-EDA, p-HPEA-EDA and 3,4-DHPEA-EA,
195
able to guarantee increases of above 50% of the total phenols in all CT oils extracted. As reported in
196
other studies, the lignans, (+)-1-acetoxypinoresinol and (+)-pinoresinol, showed the lowest
197
variability between phenolic compounds under the different operating extraction conditions for all
198
the cultivars analysed (Selvaggini et al., 2014; Veneziani et al., 2015), even though higher
199
percentage increases were found in Ottobratica and Peranzana oils extracted at 30 °C: 12.6% and
200
25.5% of the sum of lignans, respectively. The genetic origin of olives affects the phenolic
201
concentration of fruit but, at the same time, shows an important impact on the absolute activity of
202
PPO as reported in various papers (Alagna et al., 2012; Garcia-Rodriguez, Romero-Segura, Sanz,
203
Sanchez-Ortiz, & Perez, 2011; Garcia-Rodriguez, et al., 2015; Goupy, Fleuriet, Amiot, & Macheix,
204
1991; Migliorini, Cecchi, Cherubini, Trapani, Cini, & Zanoni, 2012; Sciancalepore & Longone,
205
1984; Sciancalepore, 1985). The low PPO activity of cv. Coratina could explain the lower impact of
206
the CT process in the phenolic concentration of oil extracted from this cultivar, compared to the
207
others (Goupy et al., 1991; Taticchi et al., 2013).
208
The CT was also studied in an attempt to control the lipoxygenase (LOX) pathway. In fact, as
209
described in other previous works (Garrido-Delgado et al., 2015; Selvaggini, Esposto, Taticchi,
210
Urbani, Veneziani, Di Maio, Sordini, & Servili, 2014; Taticchi, Esposto, & Servili, 2014), the high
211
temperatures (over 30 °C) reduce the formation of C6 aldehydes and esters responsible,
212
respectively, for fresh cut grass and fruity sensory notes, whereas they appear to increase the
213
alcohol production responsible for ripe fruitiness. The rapid, olive paste cooling showed
214
quantitative and qualitative modifications of volatile compounds of EVOOs, which appear to be
215
strongly connected to the olive cultivars and the effects on the activity level of the different
216
enzymes belonging to the LOX pathway.
217
A variation in the aldehyde concentration in the EVOOs, obtained from the cv. Coratina, was not
218
detected, whereas alcohols increased in the CT oils malaxed at 25 °C and 30 °C, compared to the
10
219
control, with an increase of 18.7% and 54.3% of the sum of saturated and unsaturated alcohols,
220
respectively. The percentage increases for both temperatures of malaxation were mainly due to a
221
rise in 1-hexanol and (E)-2-hexen-1-ol, probably due to a differentiated effect of the cooling process
222
on the thermal stability and relative activity of Coratina enzymes involved in the release of these
223
volatile compounds, that could have a specific response to the rapid reduction of temperature at 15
224
°C. The generally very low concentration of esters in this cultivar was reduced in both EVOOs
225
malaxed at 25 °C and 30 °C following the CT of the olive paste (Table 3). This behaviour could be
226
due to a block of the lipoxygenase pathway, characterised by a strong inhibition of alcohol
227
acetyltransferase activity of cv. Coratina at a low temperature, obtained by the rapid cooling
228
conditioning of the olive paste. Insignificant differences in the aldehyde concentration was also
229
observed for the cv. Ottobratica, whereas the alcohols showed a considerable reduction at both
230
temperatures tested: 46.2% and 15.4% of the sum of saturated and unsaturated alcohols,
231
respectively, for the CT oils extracted at 25 °C and 30 °C compared to the control samples. As
232
regards the concentration of esters, a significant variation was found in the CT oils, characterised by
233
an increase in the sum of esters of 36.1% for the oil extracted at 25 °C and 48.5% for the other oil
234
extracted at the highest temperature of malaxation (Table 3). As regards the cv. Peranzana, the data
235
showed an overall reduction in alcohols, which was more evident for the CT oil extracted at 30 °C,
236
with a 42.6% decrease in the sum of saturated and unsaturated alcohols. A high variability was also
237
observed for esters, particularly abundant in this Apulian cultivar (Leone et al., 2015; Selvaggini et
238
al., 2014; Servili et al., 2015; Veneziani et al., 2015), with an increase of 116.6% and 33.1%,
239
respectively, for the sample obtained at the lowest and at the highest temperatures tested. The
240
Peranzana oils also showed no significant modification in the sum of saturated and unsaturated
241
aldehydes compared to the control samples (Table 3). The technological innovation introduced in
242
the mechanical extraction process of the oil revealed different results of volatile composition. It
243
highlighted a large cultivar-dependency, even though the rapid cooling conditioning of olive paste
244
showed a low variability in the sum of saturated and unsaturated aldehydes of all EVOOs extracted
11
245
from the three Italian olive cultivars, with a range between -0.1% and +3.7%. The cv. Coratina
246
malaxed at 30 °C had the maximum value and the cv. Peranzana showed the minimum value, when
247
the oil was also extracted at 30 °C of malaxation. The only exception was represented by the oil
248
extracted at 25 °C from olives of cv. Ottobratica, which showed an increase of 12.9%, due to a
249
higher value of (E)-2-hexenal.
250
The experiments performed using dry ice to cool the olives directly during crushing (CT-DI) was
251
carried out to compare the impact of cooling treatment on the quality of EVOO during and post
252
crushing. Table 4 shows how the phenolic fraction of CT-DI oil maintained the same increasing
253
trend of the CT test compared to the control, and did not show significant percentage variations
254
compared to CT oil. The volatile composition of CT-DI oil showed similar changes than CT sample
255
compared to control oil (Table 5), even though the increase in the sum of saturated and unsaturated
256
aldehydes was more limited in CT-DI oil than CT oil, due to the lower amount of (E)-2-hexenal. On
257
the contrary, higher values of 1-hexanol and (E)-2-hexen-1-ol were responsible for a more limited
258
reduction in the sum of saturated and unsaturated alcohols of CT-DI oil compared to the control
259
sample.
260
The cooling treatment is a thermal conditioning widely used in the food and agro industry, but this
261
was the first time it had been applied to the mechanical extraction process of olive oil. For decades
262
the researchers have, in fact focused their technological studies on the heating of olive paste to
263
improve the oil yield and the quality of the product. Nevertheless, the rapid cooling of olive paste at
264
15 °C showed very interesting results, with a positive impact on EVOO quality, mainly related to
265
the phenolic composition. The CT determined an increase in phenolic fractions for all the cultivars
266
and at both temperatures of malaxation tested, even though the percentage increase is, however,
267
linked to the different cultivar studied. The major amounts of phenolic compounds are due to a
268
thermal inhibition of the main enzymes responsible for a process of degradation during the first
269
phase of olive oil production. Even in this experiment, the volatile composition, highlighted a
270
strictly cultivar-dependent variability (Esposto et al., 2013; Inarejos-Garcia, Fregapane, &
12
271
Desamparados Salvador, 2011; Issaoui et al., 2015; Veneziani et al., 2015;), with specific responses
272
of the enzymes of the LOX pathway of each different cultivar (Chiappetta, Benincasa, &
273
Muzzalupo, I., 2015; Padilla, Hernandez, Sanz, & Martinez-Rivas, 2009; Padilla, Martinez-Rivas,
274
Perez, & Sanz, 2012a; Padilla, Hernandez, Sanz, & Martinez-Rivas, 2012b; Patui, et al., 2010) to
275
the rapid cooling treatment of olive paste.
276
13
277
Acknowledgements
278
This study was kindly supported by Alfa Laval SpA (Tavarnelle Val di Pesa, Florence, Italy) and
279
Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR), Italy (Project CLUSTER
280
CL.A.N.−Agrifood AREA1− Nutrizione e Salute Pros.IT (CTN01_00230_413096)).
281
14
282
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457 Table 1. Evaluation of moisture and oil content of olive pomace obtained at different operative conditions.a Malaxation temperature
25 °C Control
Moisture content (%) Oil content (% d.w.)
63.9 (0.7)a 65.5 9.3 (0.5)a 10.1
Moisture content (%) Oil content (% d.w.)
63.4 (0.3)ab 61.4 12.8 (0.5)a 11.3
Moisture content (%) Oil content (% d.w.)
64.3 (0.2)ab 64.7 10.6 (0.3)a 9.8
30 °C b
CT
Control cv. Coratina (1.2)a 64.1 (0.5)a (0.2)a 9.3 (1.1)a cv. Ottobratica (1.7)a 65.0 (1.2)b (0.8)ab 12.1 (0.8)ab cv. Peranzana (0.8)a 64.3 (0.4)ab (0.4)a 10.4 (2.5)a
b
CT
63.6 (0.5)a 10.2 (1.1)a
63.3 (0.4)ab 11.0 (0.1)b 61.1 (0.6)b 11.5 (0.7)a
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-b) are not significantly different (p < 0.05). bCT = cooling treatment.; d.w. = dry weight.
458 459
22
460 Table 2. Evaluation of phenolic compounds (mg/kg) of EVOOs Control and CT extracted at different operative conditions.a Malaxation temperature
25 °C Control
30 °C b
CT
Control
b
CT
cv. Coratina 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
5.1 10.0 505.8 123.7 235.3 22.7 44.5 23.8 970.8
(0.1)a (0.2)a (1.8)a (0.5)a (0.4)a (0.01)a (0.002)ab (0.005)a (1.9)a
10.9 23.6 517.3 127.5 240.7 30.8 43.4 22.8 1016.9
(0.03)b (0.1)b (2.9)b (0.1)b (0.2)a (1.0)b (0.4)a (0.1)b (3.1)b
5.1 5.6 730.4 136.9 355.4 25.1 46.5 22.7 1327.8
(0.1)a (0.7)c (3.2)c (1.9)c (4.5)b (0.5)c (0.8)ab (0.3)b (6.0)c
7.3 7.8 741.4 138.0 368.1 27.4 47.7 21.1 1358.9
(0.2)c (0.4)d (4.2)d (1.4)c (8.0)c (0.3)d (0.6)b (0.1)c (9.2)d
(0.02)c (0.1)c (0.2)c (0.1)c (0.5)c (0.1)c (0.1)c (0.1)c (0.6)c
16.3 14.3 324.8 55.3 100.1 8.4 26.0 41.6 586.9
(0.2)d (0.2)d (8.1)d (0.9)d (1.1)d (0.1)d (0.2)d (0.5)d (8.3)d
(0.4)bc (0.1)c (4.4)c (0.2)c (1.4)c (0.04)a (0.2)ab (0.2)b (7.5)c
3.1 6.4 467.7 75.5 86.9 10.5 21.9 19.9 691.9
(0.04)c (0.1)c (8.3)d (0.6)b (1.4)d (0.2)b (3.0)b (0.3)c (9.0)d
cv. Ottobratica 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
21.5 17.1 205.0 46.3 78.0 7.3 21.5 39.5 436.2
(0.1)a (0.04)a (0.7)a (0.1)a (0.1)a (0.003)a (0.05)a (0.1)a (0.8)a
20.6 16.7 251.1 48.2 80.2 7.6 23.8 40.4 488.5
(0.03)b (0.02)b (0.6)b (0.01)b (0.1)b (0.03)b (0.1)b (0.1)b (0.6)b
23.1 13.1 297.2 50.4 94.0 9.7 23.5 36.5 547.5
cv. Peranzana 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
1.3 4.9 255.6 40.0 38.8 2.7 17.6 15.5 376.4
(0.1)a (0.2)a (1.6)a (0.2)a (0.1)a (0.04)a (0.04)a (0.007)a (1.6)a
3.8 8.8 405.6 74.5 72.6 9.7 16.8 15.2 606.9
(0.2)b (0.1)b (9.6)b (1.1)b (0.9)b (0.1)b (0.1)a (0.5)ab (9.7)b
3.6 6.5 320.2 45.4 43.8 3.7 18.5 14.8 456.5
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-d) are not significantly different (p < 0.05). bCT = cooling treatment.
461 462
23
463 Table 3. Evaluation of volatile compounds (µg/kg) of EVOOs Control and CT extracted at different operative conditions.a Malaxation temperature
25 °C Control
30 °C b
CT
Control
b
CT
cv. Coratina Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate
Aldehydes (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) Alcohols 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Esters Hexyl acetate (Z)-3-Hexenyl acetate
132 1228 153429 2139 1327 1019 938 2492 890 2760
(1)a 103 (11)b (7)a 1229 (57)a (3211)ab 156300 (283)a (149)a 2049 (2)a (123)ab 1318 (7)a (50)a (35)ab (30)a (3)a (100)a
143 (6)a 71 (6)a 100 687 100237 1532 959 528 434 5190 1893 5995
(3)a (1)a (858)a (32)a (7)a (14)a (14)a (10)a (5)a (69)a
94 (1)a 210 (1)a 218 1433 138950 2613 1632 786 766 1023 1005 1678
(3)a (6)ab (7990)a (168)a (170)a (4)a (1)a (34)a (11)a (49)a
952 (13)a 1083 (37)a
883 835 3858 876 3160
(54)b (9)a (100)b (2)a (6)b
132 1297 148179 2428 1497 1056 1023 1075 824 2810
(3)a 109 (3)b (8)ab 1351 (38)b (2000)b 154000 (3960)ab (25)b 1955 (36)a (34)b 1285 (26)a (29)a (12)b (33)c (13)b (33)a
79 (2)b 97 (8)c 36 (3)b 72 (1)a cv. Ottobratica 106 650 113545 1609 1016 536 425 1978 1534 3076
(1)b (9)b (716)b (1)b (2)b (4)a (6)a (21)b (4)b (21)b
106 572 104685 1603 1011 557 446 3762 2247 4590
(1)b (4)c (746)c (26)b (9)b (21)a (13)a (53)c (60)c (33)c
132 (4)b 128 (1)b 282 (10)b 305 (26)b cv. Peranzana 217 1439 141265 2575 1765 779 864 1135 1060 1375
(5)a (81)ab (498)a (22)ab (6)a (11)a (26)b (8)b (18)b (39)b
2616 (131)b 1793 (106)b
219 1371 115443 2791 1700 832 790 2082 1170 2981
965 873 4633 434 3570
(18)c (2)a (88)d (14)c (64)c
41 (4)d 28 (2)b 99 741 105013 1595 1001 531 423 2856 1749 4258
(1)a (5)d (446)c (22)ab (26)b (8)a (6)a (20)d (32)d (42)d
197 (6)c 446 (13)c
(6)a 138 (2)b (10)b 1536 (81)b (7414)b 116060 (503)b (36)a 2348 (61)b (65)a 1357 (32)b (29)b (12)c (4)c (1)c (33)c
1132 (40)a 1294 (42)c
762 780 1579 753 1785
(4)a (4)d (17)d (16)d (2)d
1856 (81)c 1372 (74)c
24
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-d) are not significantly different (p < 0.05). b CT = cooling treatment.
464 465
25
466 Table 4. Evaluation of phenolic compounds (mg/kg) of EVOOs Control, CT and CT-DI of cv. Ottobratica malaxed at 25 °C.a Control 3,4-DHPEA p-HPEA 3,4-DHPEA-EDA p-HPEA-EDA 3,4-DHPEA-EA Ligstroside aglycon (+)-1-Acetoxypinoresinol (+)-Pinoresinol Total phenols
20.9 17.8 199.7 47.8 76.7 7.6 22.1 39.7 432.3
(0.2)a (0.05)a (1.8)a (0.2)a (1.1)a (0.09)a (0.2)a (1.1)a (2.4)a
b
22.8 18.6 244.1 48.1 84.2 7.8 22.9 42.2 490.7
CT (0.1)b (0.2)b (2.5)b (0.9)a (1.0)a (0.1)a (0.9)ab (1.4)a (3.3)b
c
CT-DI
26.9 19.9 228.3 47.2 95.9 7.7 24.7 43.4 494.1
(0.3)c (0.4)c (4.4)c (2.4)a (4.8)b (0.4)a (1.2)b (2.2)a (7.4)b
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-c) are not significantly different (p < 0.05). bCT = cooling treatment; cCT-DI = cooling tretment - dry ice.
467
26
468 Table 5. Evaluation of volatile composition (µg/kg) of EVOOs Control, CT and CT-DI of cv. Ottobratica malaxed at 25 °C.a Control (E)-2-Pentenal Hexanal (E)-2-Hexenal (E,E)-2,4-Hexadienal 2,4-hexadienal (i) 1-Penten-3-ol (E)-2-Penten-1-ol 1-Hexanol (Z)-3-Hexen-1-ol (E)-2-Hexen-1-ol Hexyl acetate (Z)-3-Hexenyl acetate
98 674 100577 1499 964 532 429 5063 1854 5979
(5)a (3)a (1222)a (19)a (32)a (22)a (9)a (28)a (9)a (84)a
89 (3)a 207 (2)a
b
CT Aldehydes 110 (1)b 668 (5)a 109890 (2455)b 1555 (1)b 975 (25)a Alcohols 529 (17)a 439 (12)a 2058 (34)b 1462 (9)b 2897 (63)b Esters 119 (7)b 269 (3)b
c
CT-DI
90 693 106111 1919 925 537 397 2924 1398 4563
(1)c (1)b (3377)ab (6)c (50)a (6)a (14)b (12)c (1)c (52)c
129 (1)c 244 (2)c
a
Data are the mean of three independent experiments analyzed twice, and the standard deviation is reported in brackets. Values with the same letters in each row (a-c) are not significantly different (p < 0.05). bCT = cooling treatment; cCT-DI = cooling tretment - dry ice.
469 470
27
471
Highlights
472 473
Cooling treatment of olive paste during the oil processing: impact on the yield and extra virgin olive
474
oil quality.
475 476 477 478 479 480 481 482 483 484 485
• A technological innovation is introduced in mechanical extraction process of olive oil. • For the first time the olive paste is undergone to a cooling treatment (CT) after the crushing phase. • The rapid cooling conditioning of olive paste has a positive impact on extra virgin olive oil quality. • The CT improves the phenolic concentration and modifies the volatile fraction of olive oil.
28