**4. Storage of olive oil**

According to olive variety, extra virgin olive oil has different sensorial attributes, e.g. fragrance, flavour, colour and nutrient composition parameters. Thus, its quality can be considered from diverse points of view: normative, commercial, nutritional, therapeutic and sensorial. An excellent olive oil is produced with good olive growing, harvesting, storage and processing practices. This condition considers the preservability an olive oil qualitative characteristic.

Some quality parameters of extra virgin olive oil (acidity, peroxide value and UV absorbance) can vary depending on time and storage method, reaching undesirable values at the end of the shelf life. Acidity increases with time, both in oils stored in the dark and exposed to light (Gómez-Alonso et al., 2007). Nowadays, consumers are imposing an increasing demand for a higher quality of extra virgin olive oil during the shelf life period. This is due to the expectation for a safe food and also for a reduction to a minimum of undesired changes in sensorial quality (Hrncirik & Fritsche, 2005).

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

availability is limited (Psomiadou & Tsimidou, 2002).

many vitamins (as A and B2) are photosensitive.

even faster in direct sunlight.

light exposition.

characteristic.

**4. Storage of olive oil** 

The adoption of proper operations is also important in the preliminary phase of olive oil storage, as for example the laminar filtration by using of cartridges closed in steel cylinders that reduce the air exposition, or the filtration under nitrogen, in controlled atmosphere.

The oxygen plays an important role on the entire and complex interactions in the olive oil. Also antioxidant molecules are strongly influenced by oxygen presence. A study of changes in total polar phenols, α-tocopherols, β-carotene, lutein, chlorophyll and squalene contents during autoxidation indicated that most interactions may be suppressed if oxygen

Another principal harmful agent of olive oil is light, both direct and diffused and in general the UV area in the light spectrum at high energy, from 290 to 400 nm is the most charged. The electromagnetic radiations promote some chemical and biochemical reactions responsible of qualitative degradation as the lipid oxidation in the presence of air. In the absence of air, however, direct sunlight causes a decrease in peroxide and Kreis values of the oil. In particular, in a study on several olive oil packaging typologies, Kiritsakis (1984) revealed that the oil oxidation proceeded slowly in darkness, faster in diffused light and

Moreover several natural substances have the property to absorb much the incident light and, for it, to originate alterations and/or undesirable variations. Pigments have this characteristics and colour degradation is in fact an unavoidable and well known event:

The temperature controls many of reactions catalyzed by enzymes. For each increase or diminution of it a variation of biological food activity is shown. At low temperatures the kinetic energy of reagent molecules decreases, the drop of mobility and collisions necessary for the formation of enzyme-substrate complex and their products occurs. Some studies (Gambacorta et al., 2004; Kanavouras & Coutelieris, 2006; Pristouri et al., 2010) demonstrated that high storage temperatures modify the olive oil quality, but less than the

According to olive variety, extra virgin olive oil has different sensorial attributes, e.g. fragrance, flavour, colour and nutrient composition parameters. Thus, its quality can be considered from diverse points of view: normative, commercial, nutritional, therapeutic and sensorial. An excellent olive oil is produced with good olive growing, harvesting, storage and processing practices. This condition considers the preservability an olive oil qualitative

Some quality parameters of extra virgin olive oil (acidity, peroxide value and UV absorbance) can vary depending on time and storage method, reaching undesirable values at the end of the shelf life. Acidity increases with time, both in oils stored in the dark and exposed to light (Gómez-Alonso et al., 2007). Nowadays, consumers are imposing an The olive oil storage could be shorter as possible: its assumption could not exceed the production year: the oil gains the excellence about 3-8 months after production, after that its quality starts decreasing. This behaviour depends on the olive cultivar and on the alteration of fatty fraction.

During storage the oil tends to loss the typical pigmentation and the aromatic characteristics of bitter and spicy, showing too many transparency and brilliance. Immediately after oil extraction, the flavour appears too strong and also characterized by an unpleasant aftertaste. If the olive oil is stored properly, as in well-sealed packages, it can reach the second storage year maintaining its sensory properties.

A good quality olive oil with a low acidity degree preserves its opacity for a long time. This is a characteristic of some oils, as those extracted from first harvested olives not yet completely ripe, which are very fruity and with low free acidity. The consumption of these oils, also named "new oils" is recommended up to a few weeks after bottling. For many consumers the cloudy olive oil represents a certainty of authenticity and it is also preferred in particular when the oil is purchased directly at the oil mill. It is characterized by a certain water amount (about 2-4 g/kg ) and residual solids as pectins, hemicelluloses, cellulose and mucilages in form of emulsion containing active or latent enzymatic activities as lipoxygenase, polyphenoloxidase and, principally, some esterases able to hydrolyze oleuropein, di-methyl-oleuropein and ligstroside aglycon derivatives responsible of bitter and sour flavour in virgin olive oils. The association between the natural and the healthy/nutritional aspect does not correspond to a scientific assessment because the presence of cloud induces the phenols degradation, which results in sensory changes.

Moreover fermentative processes develop on olive polysaccharides with transfer of compounds which confer sludge and warmed defects to the extracted oil. Thus, the filtration operation appears necessary, indeed is advisable before bottling and also before storage with the scope to maintain a major shelf life, avoiding settling and frequent decanting operations, which in turn induce a higher oxidation. The industrial filtration can be conducted by several systems, which differ for used material: hydrophilic cotton or cellulose at high porosity are better than fossil flour which reduces the antioxidant property because acts directly on *o*diphenols, decreasing the amount in the olive oil and so its shelf life (Ricci, 2007).

The oil storage is favoured by the antioxidants content that prevents the rancidity, but their activity initially slows and then stops with successive formation of free radicals. This action can be enhanced by improper storage practices: for example, when storage temperature is not controlled, or when the oil is held in contact with the direct light and or at high temperatures at consumer's house, or when an improper sealing is applied after the first container opening. Concerning this last aspect, the use of screw caps is more advisable than metal pourers which expose the oil to the oxidative agents.

As the extra virgin olive oil extraction is conducted with controlled temperatures lower than 28 °C, as the extra virgin olive oil storage requests the same attention. It has to be done with control of temperature, which may range from 10 °C to 18 °C: the correct storage temperature is 14-15 °C. The high temperatures increase the chemical variation velocity and the major oil fluidity. This last effect promotes the oxygen permeation. When storage temperature decreases at 8-9 °C, white deposits can appear in the oil, due to triglyceride crystallization. The higher is the content of saturated glycerides, the higher is the freeze process. The step from the oil crystallization to the solidification by lower temperatures (3-4 °C) slightly increases the oil stability to the oxidation and gives substantial modifications in the sensory profile. If the clear colour maintains beside the transfer of solidified oils to warmer places, it possible that a margarinization process involved or mucilage could be present.

Packaging and Storage of Olive Oil 209

in bottle filling operation. In particular, bottles are hooked up by a special machine, which invert them and blow inside liquid nitrogen, which becomes gas when comes in contact with the environment, dilutes and moves out the oxygen present in the free volume of the

Then, bottle straighten up and proceeds toward the filling operation during which nitrogen stays inside because is heavier than air. As the bottle fills up and the oil level goes up, the nitrogen is carried outside avoiding anyway the oxygen penetration. The velocity of successive capping guarantees that only presence of nitrogen between cap and oil (Soressi,

Using of inert gases, as argon and nitrogen, can solve many problems and provide an optimal product storage in several production steps, as pressing, kneading and, most of all, storage and bottling. A study demonstrated in fact, that extra virgin olive oils collected from the previous harvesting season and stored under nitrogen atmosphere could be packaged in glass bottles without appreciable quality changes, as compared with seasonal extra virgin olive oil packaged in similar bottles (Guil-Guerrero & Urda-Romacho, 2009). Nitrogen is the most used gas to protect oil from the air contact, able to remove oxygen by container headspace and pre-formed volatile contaminants. Bottling lines are very versatile for packaging typologies and easily cleanable. A past research on Italian plant typologies revealed that the prevalent packaging line is the semi-automatic (50%), followed by the automatic (27%) and manual (23%) ones. The first and the third show a low specialization

Bottle capping can be carried out by means of cork or more frequently by metal caps. A good quality cork has not to be porous and present fungal contaminants, however it is not suggested as may cause early deterioration, due to its high oxygen permeability. Metal caps are provided of a screw and a plastic soft liner that permit a perfect airtight acting as dripper. Also a thermally retractable capsule can be present on cap to seal the packaging and improve the product from the esthetical point of view. Just these last are the most used

In Italy and in the world the majority of consumers purchases bottled olive oil. Nowadays attention of many actors is focused on olive oil packaging, in particular on container design that often communicates the natural concept and territory link associated to the contained olive oil. Due to the changed life-style, oil container manifests also a functional

The nature of the packaging material has a notable influence on oil quality (Gutierrez et al., 1988). In general, a packaging is chosen depending on several criteria as product stability, environmental conditions to which food will be exposed during storage and distribution, and the product nature. In particular, the basic factors that may alter the quality of packed

ones (72%) respect to ones with a simple screw (15%) and cork (11%) (Ricci, 2007).

bottle.

2009).

process level and a limited bottling capacity.

**5.2. Olive oil packaging materials** 

property.

oils are:

Finally, it is important that storing and packaging facilities respect hygiene and healthiness standards. Aromatic polycyclic hydrocarbons and benzene present in the atmosphere are absorbed by the oils contained in not hermetically sealed packages (Ricci, 2007).
