*3.4.1. Use of the technological co-adjuvants in malaxation*

According to the UE 2568/1991 and 1989/2003 standards, co-adjuvants can be added during malaxation to break down emulsions and at the same time to guarantee a high oil extraction yield. In particular, the most frequently employed co-adjuvants are micronized talc and in some countries, although not in Europe, enzyme preparations are used.

Such enzyme preparations act on the structural colloids of the cells of not only the pulp, but also the skin and assist the activity of the endogenous enzymes (pectinases, cellulases and hemicellulases) resulting in an increase in the olive oil yield and in its quality (Vierhuis et al., 2001). In particular, it has been demonstrated that enzyme preparations tend to increase the phenolic content in VOO (Table 3). However, these effects are found only when working with olives characterized by an early ripening (Ranalli & Serraiocco, 1996; Ranalli & De Mattia, 1997; Vierhuis et al., 2001; Montedoro et al., 2002). In fact, the use of enzymatic preparations in olives when they have reached an advanced stage of ripening does not lead to any qualitative or quantitative benefit. This is due to the fact that the structural colloids in mature olives, on which the aforementioned enzymes should act, have already been degraded by the endogenous enzymatic activity during the ripening of the fruit (Heredia et al., 1993). Therefore, the addition of enzymatic preparations would be useless in this case.

However, the EU regulations 2568/1991 and 1989/2003 do not allow the addition of enzymatic preparations, whereas they authorise the use of micronized talc as co-adjuvant. The use of talc as a co-adjuvant has been proved important to increase oil extraction yield without any interference to the quality of VOO. The amount of talc used ranges from 0.7 to 1.5% of the weight of the olives being milled after the first 10 minutes of the process. In fact, its addition to difficult pastes improves the paste structure and reduces emulsions. This product acts on the olive pastes by increasing the drainage effect and, therefore, improving the efficiency of solid-liquid separation during centrifugation of the crushed pastes (Servili et al., 2004b). The micronized talc can be added to the pastes during malaxation (0.7-1.5% of the paste weight) after the first 10 minutes of the trial. Several studies carried out on Italian cultivars show that the use of the micronized talc does not involve any negative effects on oil quality and, in some cases, its use leads to a meaningful increase in the extraction yield (Servili et al., 2004b).


**Table 3.** Phenolic composition of virgin olive oil (mg/kg) with and without enzymatic treatment during malaxation (Vierhuis et al., 2001).

a The phenolic content is the mean value of three independent experiments (standard deviation). Values in each row bearing the same superscripts are not significantly different from one another (P < 0.05).

### **3.5. Olive oil extraction systems**

162 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

*3.4.1. Use of the technological co-adjuvants in malaxation* 

some countries, although not in Europe, enzyme preparations are used.

(Figure 3, Table 2).

et al., 2008).

In conclusion, it can be considered that, as regards the process variables adopted during malaxation, the temperature should be set within the range of 24-27 °C, both for the traditional and for the new malaxer (i.e., the confined malaxer), while process times greater than 35-40 minutes may result in a large loss in terms of product quality (in particular in the traditional malaxer) without producing significant positive effects on the oil extraction yield. Special attention must be paid to the control and regulation of oxygen percentage in contact with the olive paste during malaxation to optimize the phenolic content as well as the flavour of VOO. This new operating parameter can be used to act on the phenolic concentration of the pastes and, therefore, of the oils, excluding negative collateral effects on the volatile compound content of the product (Servili et al., 2003a; Migliorini et al., 2006; Servili et al., 2008). In fact, the traditional Italian *cvs* differ with respect to their content of phenolic substances and, because of this difference, the phenolic concentration in oil must be optimized; this optimization can be obtained by regulating their oxidative degradation level during malaxation. Thus, malaxation should be carried out without oxygen for the *cvs* with low phenolic concentration, whereas malaxation should be carried out with controlled supplementation of oxygen for those *cvs* characterized by higher phenolic concentrations

Moreover, it must be pointed out that no additional gases, such as nitrogen or argon, are required inside the head space in the confined malaxer to avoid the presence of oxygen. In fact, if the malaxer is filled with crushed paste during the process, the olive tissues of pastes naturally release carbon dioxide (CO2) (Weichmann, 1987), whereas the limited amount of oxygen they adsorb during the crushing process will be consumed rapidly by endogenous enzyme activities. As a consequence, the malaxer head space will be naturally saturated by an inert gas, such as carbon dioxide (Servili et al., 2003a; Parenti et al., 2006a, 2006b; Servili

According to the UE 2568/1991 and 1989/2003 standards, co-adjuvants can be added during malaxation to break down emulsions and at the same time to guarantee a high oil extraction yield. In particular, the most frequently employed co-adjuvants are micronized talc and in

Such enzyme preparations act on the structural colloids of the cells of not only the pulp, but also the skin and assist the activity of the endogenous enzymes (pectinases, cellulases and hemicellulases) resulting in an increase in the olive oil yield and in its quality (Vierhuis et al., 2001). In particular, it has been demonstrated that enzyme preparations tend to increase the phenolic content in VOO (Table 3). However, these effects are found only when working with olives characterized by an early ripening (Ranalli & Serraiocco, 1996; Ranalli & De Mattia, 1997; Vierhuis et al., 2001; Montedoro et al., 2002). In fact, the use of enzymatic preparations in olives when they have reached an advanced stage of ripening does not lead to any qualitative or quantitative benefit. This is due to the fact that the structural colloids in Different extraction technologies, such as pressure and centrifugation and selective filtration (i.e. "surface tension" or "percolation") enabling the separation of oily must from the olive paste can be used (Boskou, 1996; Di Giovacchino et al., 1994, 1995).

#### *3.5.1. Pressure extraction system*

Pressing is one of the oldest methods of oil extraction and has evolved considerably over the centuries. In olive oil mills equipped with this system the press separation of the oil from the paste is currently carried out using open hydraulic presses, whereas close cage presses have almost disappeared not only due to high purchase prices, but also to their maintenance costs. The previously malaxed paste is subsequently stratified on stacked filter mats, each

covered with approximately 0.5 inches (1.25cm) of paste and interposed with metal disks. This operation is carried out mechanically thanks to a dispenser, which takes the paste from the malaxer and stores it on the nylon and/or polypropylene filter mats. Both types of filter mats have a central hole to allow the expressed oil and water (olive juice) to exit in both directions. From a theoretical point of view, this system guarantees intrinsic oil quality. However, its use presents a few problems, mainly due not only to its low working capacity per hour, in which case the storage of olives lengthens, but also to the proper use of the filter mats and to the types of materials used to build the equipment. The critical aspects of the process regarding the use of the press, which impacts on the quality of the oil, are concerned with both the proper management of the filter mats and the use of construction materials made of stainless steel. As regards the filter mats, it is important to point out that they can represent a source of contamination, due to fact that they may introduce fermentation and an oxidation defect into the oil, causing sensorial defects (Angerosa et al., 2004). This effect can arise both from the contamination with oils obtained from poor batches of olives and from fermentation processes of the vegetation water and pomace fragments, which remain in the filter mats, when they are kept in storage during the different processing stages. The latter problem occurs particularly when the oil harvest is interrupted by bad climatic conditions and it is impossible to work continuously. In order to minimize the risk of defects developing in the VOO, it would be desirable: i) to work in a continuous cycle; ii) to change the stacked filter mats frequently during the process and to clean them periodically using a pressure washer; iii) to store the aforementioned filter mats at a low temperature (0 °C-5 °C) to avoid fermentative processes during breaks in the oil processing.

Technological Aspects of Olive Oil Production 165

1. Traditional three-phases decanters, featuring water addition ranging from 0.5 to 1

2. Two-phases decanters, which can operate without the addition of water and do not

3. New three-phases decanters, working at low water consumption ranging from 0.2 to 0.3

The traditional three-phases decanters, which allow the oil to be separated both from the vegetation water and from the pomace, feature a humidity level of between 50% and 55% and dilute the pastes produced to reduce their viscosity. In doing so, they facilitate separation of the oil-vegetation water with a dilution ratio ranging from 1:0.5 to 1:1 (from 50 to 100 l of water for every 100 Kg of paste to be decanted). In addition to the enormous amounts of vegetation water which have to be drained, this implies a decrease in the oil quality, principally due to the washing away of the phenolic compounds of the product, with massive decreases in this important antioxidant fraction (Ranalli & Angerosa, 1996; Servili et al., 1999c, 1999d; Stefanoudakii et al., 1999; Di Giovacchino et al., 2001; Servili &

The evolution of this technology has lead to the production of two and three-phases decanters with low water consumption. By using these new systems, the extracted oils feature a higher phenolic concentration than those extracted by means of the traditional centrifugation process, because the loss of these hydrophilic phenolic compounds in the vegetation water is reduced (Table 4) (Servili et al., 1999d). In this context, it is important to point out how these new extraction systems, which do not take into account the addition of water, enable high quality VOOs to be obtained. The focus of this problem consists in linking together the low processing temperatures with a reduced use of water dilution in the pastes: by using centrifugation systems, these two process variables should allow high

compounds **two phase**<sup>s</sup> **three phase**<sup>s</sup> **two phase**<sup>s</sup> **three phase**<sup>s</sup> 3,4 DHPEA 0.87 ± 0.02 0.58 ± 0.08b 0.66 ± 0.11a 0.50 ± 0.11a p-HPEA 3.74 ± 0.07a 2.34 ± 0.08b 3.30 ± 0.10a 4.22 ± 0.10b Vanillic acid 0.41 ± 0.01a 0.19 ± 0.01b 0.26 ± 0.01a 0.14± 0.05b Caffeic acid 0.16 ± 0.01a 0.12 ± 0.02b 0.09 ± 0.01a 0.21 ± 0.03b 3,4 DHPEA-EDA 522.2 ± 13.5a 427.2 ± 13.8b 30.09 ±1.03a 18.53 ± 0.68b p-HPEA-EDA 78.16 ± 0.52a 67.26 ± 2.55b 20.99 ± 0.82a 22.40 ± 0.33a Lignans 38.41 ± 0.10a 35.62 ± 1.11b 48.00 ± 3.40a 46.72 ± 5.78a 3,4 DHPEA-EA 351.7 ± 11.0a 244.9 ± 13.6b 68.01 ± 6.00a 52.04 ± 3.11b Total polyphenols 673 ± 4a 585 ± 7b 304 ± 5a 263 ± 4b Induction period [h] 17.8 ± 0.1a 15.5 ± 0.2b 5.2 ± 0.1a 4.6 ± 0.1b **Table 4.** Effect of water reduction during centrifugation on the phenolic composition of virgin olive oil

Data are the mean values of three independent experiments ± standard deviation. Values in each row,

with cvs with different letters, are significantly different from one another (p < 0,01).

*Coratina* **cv.** *Ogliarola* **cv.**

produce vegetation water as a by-product of the extraction oil process.

m3/ton.

m3/ton.

Esposto, 2004).

Phenolic

(mg/kg) (Servili et al., 2002).

As regards the materials used to construct the press, all the metallic parts which come into contact with the product must be made of, or at least covered with stainless steel to avoid the transfer of metals, especially those metals which can speed up the oil oxidation, to the oil during the extraction process.

#### *3.5.2. Extraction by centrifugation*

The majority of VOO is currently extracted by centrifugation in Mediterranean countries. The idea of exploiting direct centrifugation of the malaxed paste to extract the oil dates back to the late nineteenth century, when the use of the first decanter applied to food industries was widespread. In the olive oil sector, this idea determined technological innovations in the VOO mechanical extraction process, which were opposed to the traditional press. The first operating patents, including the patent by Corteggiani, date back to 1956, followed by new companies producing olive oil machines in the early sixties. This machine, called a decanter, consists of a drum containing a cylindrical and a conical part with a horizontal axis, inside which an additional cylinder worm is placed, which acts as a screw conveyor. The differential speed of the latter is slower than that of the outer drum in order to discharge the solid part. In recent years, this extraction system has evolved considerably in order to reduce the amount of water used during the process. In fact, the decanters can be classified as follows:

1. Traditional three-phases decanters, featuring water addition ranging from 0.5 to 1 m3/ton.

164 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

to avoid fermentative processes during breaks in the oil processing.

during the extraction process.

classified as follows:

*3.5.2. Extraction by centrifugation* 

As regards the materials used to construct the press, all the metallic parts which come into contact with the product must be made of, or at least covered with stainless steel to avoid the transfer of metals, especially those metals which can speed up the oil oxidation, to the oil

The majority of VOO is currently extracted by centrifugation in Mediterranean countries. The idea of exploiting direct centrifugation of the malaxed paste to extract the oil dates back to the late nineteenth century, when the use of the first decanter applied to food industries was widespread. In the olive oil sector, this idea determined technological innovations in the VOO mechanical extraction process, which were opposed to the traditional press. The first operating patents, including the patent by Corteggiani, date back to 1956, followed by new companies producing olive oil machines in the early sixties. This machine, called a decanter, consists of a drum containing a cylindrical and a conical part with a horizontal axis, inside which an additional cylinder worm is placed, which acts as a screw conveyor. The differential speed of the latter is slower than that of the outer drum in order to discharge the solid part. In recent years, this extraction system has evolved considerably in order to reduce the amount of water used during the process. In fact, the decanters can be

covered with approximately 0.5 inches (1.25cm) of paste and interposed with metal disks. This operation is carried out mechanically thanks to a dispenser, which takes the paste from the malaxer and stores it on the nylon and/or polypropylene filter mats. Both types of filter mats have a central hole to allow the expressed oil and water (olive juice) to exit in both directions. From a theoretical point of view, this system guarantees intrinsic oil quality. However, its use presents a few problems, mainly due not only to its low working capacity per hour, in which case the storage of olives lengthens, but also to the proper use of the filter mats and to the types of materials used to build the equipment. The critical aspects of the process regarding the use of the press, which impacts on the quality of the oil, are concerned with both the proper management of the filter mats and the use of construction materials made of stainless steel. As regards the filter mats, it is important to point out that they can represent a source of contamination, due to fact that they may introduce fermentation and an oxidation defect into the oil, causing sensorial defects (Angerosa et al., 2004). This effect can arise both from the contamination with oils obtained from poor batches of olives and from fermentation processes of the vegetation water and pomace fragments, which remain in the filter mats, when they are kept in storage during the different processing stages. The latter problem occurs particularly when the oil harvest is interrupted by bad climatic conditions and it is impossible to work continuously. In order to minimize the risk of defects developing in the VOO, it would be desirable: i) to work in a continuous cycle; ii) to change the stacked filter mats frequently during the process and to clean them periodically using a pressure washer; iii) to store the aforementioned filter mats at a low temperature (0 °C-5 °C)


The traditional three-phases decanters, which allow the oil to be separated both from the vegetation water and from the pomace, feature a humidity level of between 50% and 55% and dilute the pastes produced to reduce their viscosity. In doing so, they facilitate separation of the oil-vegetation water with a dilution ratio ranging from 1:0.5 to 1:1 (from 50 to 100 l of water for every 100 Kg of paste to be decanted). In addition to the enormous amounts of vegetation water which have to be drained, this implies a decrease in the oil quality, principally due to the washing away of the phenolic compounds of the product, with massive decreases in this important antioxidant fraction (Ranalli & Angerosa, 1996; Servili et al., 1999c, 1999d; Stefanoudakii et al., 1999; Di Giovacchino et al., 2001; Servili & Esposto, 2004).

The evolution of this technology has lead to the production of two and three-phases decanters with low water consumption. By using these new systems, the extracted oils feature a higher phenolic concentration than those extracted by means of the traditional centrifugation process, because the loss of these hydrophilic phenolic compounds in the vegetation water is reduced (Table 4) (Servili et al., 1999d). In this context, it is important to point out how these new extraction systems, which do not take into account the addition of water, enable high quality VOOs to be obtained. The focus of this problem consists in linking together the low processing temperatures with a reduced use of water dilution in the pastes: by using centrifugation systems, these two process variables should allow high


**Table 4.** Effect of water reduction during centrifugation on the phenolic composition of virgin olive oil (mg/kg) (Servili et al., 2002).

Data are the mean values of three independent experiments ± standard deviation. Values in each row, with cvs with different letters, are significantly different from one another (p < 0,01).

quality oils and machines featuring high yields to be obtained (Ranalli & Angerosa, 1996; Servili et al., 1999d; Stefanoudakii et al., 1999; Di Giovacchino et al., 2001).

Technological Aspects of Olive Oil Production 167

frequently employed in the oil mills consist of a series of perforated, truncated cone-shaped disks, mounted on the hollow shaft-mounted drum in order to leave a free space of

Centrifugal force forces the oily must poured in from the top through the hollow drum shaft upwards and it is divided into three different layers of oil, vegetation water and impurities, according to their specific weight. The drum diameter of decanters used in the oil mills ranges from 400 to 700 mm, with a rotational velocity ranging from 5000 to 12000 rpm. The working capacity of these machines in terms of litres of oily must poured in per hour is very high and it varies between 500 and 2000 l/h. The work carried out by the vertical centrifuges is qualitatively satisfactory, even though there is often a loss of oil in the vegetation waters. This loss cannot exceed 500 g/ton of processed olives if centrifugation process is to be

During storage, the phenolic composition of EVOO is modified by the endogenous enzymatic activities contained in the cloudy phase. These enzymes may reduce the "pungent" and "bitter" sensory notes, the intensity of which is strictly linked to the content of aglycon secoiridoids, and, at the same time, can produce olfactory and taste defects. Oil filtration partially removes the water and enzymes from EVOOs, and enables the EVOO phenolic content to stabilize during its storage. The filtration process of EVOO is a procedure carried out in two steps: first, the suspended solids are removed, and second, the elimination of humidity gives the oil a brilliant aspect. Normally, organic or inorganic materials are used in conjunction with a variety of filtration equipment to enhance or enable the separation of suspended solids and water-oil. The type of such equipment, often called filter aids, depends on the final objective (Montedoro et al.,

The olive oil profile changes during its storage, due to the simultaneous, drastic reduction in compounds from the LOX pathway and to the neo-formation of volatile compounds, responsible for some common defects referred to as "rancid", "cucumber" and "muddy

This runs parallel to the increase in saturated aldehydes nonanal, and above all hexanal in the oxidation process, but it cannot be considered a useful marker of oxidation, since it is also present in the aroma of high quality EVOOs (Angerosa et al., 2004; Servili et al.,

Furthermore, the presence of sediment as a result of the decantation of unfiltered olive oil during its storage can determine, under suitable temperature conditions, the production of unpleasant compounds responsible for the typical "muddy sediment" defect due to the fermentation which produces compounds, probably of the butyric type (Angerosa et al.,

sediment" (Morales & Aparicio, 1997; Angerosa et al., 2004; Servili et al,. 2009a).

approximately 1 mm between the disks.

considered adequate.

**3.7. Olive oil storage** 

2005).

2009a).

2004; Servili et al., 2009a).

As regards the by-products obtained by centrifugation, it is important to recall here that, whereas the aforementioned problem concerning the use of three-phases traditional systems is represented by the enormous amounts of vegetation water to be drained (0.7-1.2 m3/ton), the main problem, when using the two-phases systems, is not only a decrease in oil quality, but also the high humidity level of the pomaces (50% for the traditional three-phases decanters, 55-60% for the two-phases). This last aspect implies two disadvantages: i) where to store by-products of the extraction process; ii) how to transport to the pomace oil factory and their subsequent use for residual oil recovery by solvent extraction.

The pomaces produced by two-phases system are generally employed for the production of compost or for spreading to improve agriculture soil, following a process similar to that used for the vegetation water of olives. In this context, three-phases decanters with low water consumption can represent an adequate alternative with respect to the two-phases extraction system, because they allow a quality of oil to be obtained which is comparable to that of oils obtained using the two-phases system, and pomaces with a reduced humidity content, similar to those produced by the traditional three-phases systems. On the contrary, they produce a certain amount of vegetation waters, which imply water draining procedures which comply with the regulations of the law.
