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New technologies for the filtration of olive oil

This practice is being adopted by all factories, even the smaller ones. It is not useful to preserve extra virgin oil in nitrogen if sludges are not cleaned first. Strategies for a long shelf life

Preservation of olive oil is becoming an ever growing concern in the Italian farms and oil factories.

In order to wait for the best condition to sell or to guarantee a long term expiration date, it is necessary to leave the extra virgin oil in the tubs of the factories or in bottles for several months.

The challenge is represented by a consumer who is more and more informed, who has legitimate expectations on the quality of the product.

Thus, the filtration becomes an essential process which can be executed hours or days after the production. Among the different schools of thought, there are those who argue that pouring dirty oil in the tubs represents an useless waste of time and energy and those who, on the contrary, argue that filtrating a few days after part of the sludges have already deposited is more effective. Truth is, everything relies on the impurity of the oil coming out of the separator. If the extra virgin is severely dirty, the cardboard filters get clogged fast, thus supporting the theories of the supporters of delayed filtration.

However, these approaches are always confronting themselves for the only reason that the one effective tool for filtrating especially at the level of a small-sized or medium-sized factory, is the cardboard filtering. This is an easy technology, accessible and inexpensive, but also responsible for filtering away 20% of biophenols of oil.

Research has been looking for alternative solutions since the nutritional and organoleptic organoleptic relevance of these biologically active compounds has been evidenced. Today, we can discuss two of these solutions, which look very different in their conception but which are both equally effective, according to experimental data, and commercialized.

The filtration by means of inertial gas has been developed and patented by the research group of Lorenzo Cerretani, who is with the Food Science Deprtment at Bologna University, implies the gurgling of an inertial gas (nitrogen or argo) in a tub which was projected right for this purpose. This technique gave excellent results even on limited quantities, from 50 up to 300 liters per hour. Other than filtering without losing biophenols, protection from oxidation is achieved as well, since the oil oxygen is substituted by inertial gases, thus reducing the oxidative power and securing a longer conservation of the product. The cost of such a technology is estimated to be 3-4 euro every 100 liters of filtered oil if nitorogen is utilized, 6-8 euro per 100 liters with argon.

The bag filtration is instead well known and used in the wine industry. Its main issue is that the filters used with wine could not be used with olive oil such as they were, so that an intense investigation was necessary to find specific filters. For instance, studies on this subject were carried out by a team coordinated by Claudio Cantini and Graziano Sani at Cnr-Ivalsa, which experimentally tested the effectiveness of such a filter on both oil which just came out of the separator (torpidity ntu > 1000) and oil which was left to sediment for a few days. (500-600 ntu). This technology was able to produce a perfectly transparent oil, with a torpidity of 30 ntu, which can be lowered to 25-30 in case of a double filtration. It is worth remarking that this process does not affect biophenols and that the material used for the production of filters, that is to say polypropylene, is well known for his chemical inertia.

by Alberto Grimelli
06 july 2009, Technical Area > Olive & Oil

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