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<pre>Dear friends.

During my visits to large olive oil mills/processors in Europe and Argentina, I
have seen that a larger number have a nitrogen blanket at the top of their
storage tanks to avoid oxygen coming in contact with the oil, ie to avoid
oxidation. At least, that is what I understood to be the reason.

Does anyone of you have more specific knowledge of the chemical/physical process
taking place when nitrogen is supplied to the storage tank?
Is the oxygen absorbed by the nitrogen or is sitting on top of the nitrogen
layer?
Is there any known risk of reaction between the oil and nitrogen, ie any
negative effects for the oil over time of storage?

Thank you for helping me with these questions.

Knut Kammann
Lakelands Olives
Clandulla/Australia


[Non-text portions of this message have been removed]
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<pre>Knut,

Lakelands Olives wrote:

> Dear friends.
>
> During my visits to large olive oil mills/processors in Europe and Argentina,
I have seen that a larger number have a nitrogen blanket at the top of their
storage tanks to avoid oxygen coming in contact with the oil, ie to avoid
oxidation. At least, that is what I understood to be the reason.

Absolutely!

> Does anyone of you have more specific knowledge of the chemical/physical
process taking place when nitrogen is supplied to the storage tank?
> Is the oxygen absorbed by the nitrogen or is sitting on top of the nitrogen
layer?

The Nitrogen excludes Oxygen from the top surface of the oil. Any oxygen
that may still be around is OUTSIDE the container. In other words, the
Nitrogen replaces the air (and hence the Oxygen).

>
> Is there any known risk of reaction between the oil and nitrogen, ie any
negative effects for the oil over time of storage?

Nitrogen is an inert gas. It reacts with very few things, so the risk of
interaction with the oil is miniscule (if not exactly zero, which I
believe to be the case!).

>
>
> Thank you for helping me with these questions.
>
> Knut Kammann
> Lakelands Olives
> Clandulla/Australia
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
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<pre>The Nitrogen excludes Oxygen from the top surface of the oil. Any oxygen
that may still be around is OUTSIDE the container. In other words, the
Nitrogen replaces the air (and hence the Oxygen).

What do you mean with outside the container? Is it an open container?

Or, as is more likely, is it a closed container and the nitrogen has forced
out the air? Does that mean that pure nitrogen will settle below air if
filled into the headspace of a tank, and ultimately, if enough nitrogen has
been filled into the headspace, all air will have been displaced?

It will be necessary to constantly add more nitrogen to the tank as it is
emptied. The top of the tank must therefore be pressurised very slightly
with a feed from a nitrogen source operating through a pressure regulator.

There must also be a pressure relief valve to relieve gas when oil is filled
into the tank and a vacuum relief valve in case the nitrogen supply fails
(to prevent the tank from collapsing).

Does someone know of a device that enables nitrogen to be filled into the
headspace of bottles before sealing?

Kurt Kupper
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<pre>Andrea and Kurt Küpper wrote:

> The Nitrogen excludes Oxygen from the top surface of the oil. Any oxygen
> that may still be around is OUTSIDE the container. In other words, the
> Nitrogen replaces the air (and hence the Oxygen).
>
> What do you mean with outside the container? Is it an open container?

Not usually, though it might work, depending on the physics of relative
densities of oxygen and nitrogen.

> Or, as is more likely, is it a closed container and the nitrogen has forced
> out the air? Does that mean that pure nitrogen will settle below air if
> filled into the headspace of a tank, and ultimately, if enough nitrogen has
> been filled into the headspace, all air will have been displaced?

Probably best to purge the vessel with Nitrogen before filling, then any
oil that goes in will not have contacted Oxygen. Might be a bit
expensive in terms of the amount of Nitrogen required, but better for
the oil.

> It will be necessary to constantly add more nitrogen to the tank as it is
> emptied. The top of the tank must therefore be pressurised very slightly
> with a feed from a nitrogen source operating through a pressure regulator.
>
> There must also be a pressure relief valve to relieve gas when oil is filled
> into the tank and a vacuum relief valve in case the nitrogen supply fails
> (to prevent the tank from collapsing).

Not sure of the details here, not having had this equipment. But, I
suspect you may be right. Some vessels have an adjustable cap that fits
inside the container and "floats" on the oil with a small amount of
Nitrogen between them. As the oil is removed for bottling, the cap is
moved down the vessel. The top of the vessel is, I believe, open to the
atmosphere. This system overcomes the pressure problem and reduces the
amount of Nitrogen required. Might be better asking the suppliers of
these things (Olives Aust? or Aust Olive Oil Supplies) about the details.

>
>
> Does someone know of a device that enables nitrogen to be filled into the
> headspace of bottles before sealing?

Will probably be a purge filling mechanism, where the bottle is first
filled with Nitrogen and then with oil, and corked or capped. This would
leave the headspace with the last of the Nitrogen above the oil.
I am unsure whether these be available locally. Again, probably worth
while asking suppliers of filler machines about this.

John Attwood
Tamworth
(Northern) NSW AU

>
>
> Kurt Kupper
>
>
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<pre>Regarding olive oil quality.

Overstored olives before processing increase free fatty acid, fusty and
musty attributes when the oil is extracted.

Poorly stored olive oil increases the peroxide value. Peroxide value
increases when the oil is brought into contact with air. ie partly
filled containers with a large headspace. Using nitrogen or some other
suitable gas that is non toxic and non reactive eg carbon dioxide can
reduce the effects of oxygen on the oil. When Nirogen is introduced it
is a stream of gas under pressure, so if the correct technique is used
the air is flushed out so that the actual oxygen concentration is much
reduced. That is debating as to whether air its on top or on the bottom
is largely an academic question.

My advice is to have well filed containers with a nitrogen atmosphere.
Particularly oil in tanks - these should also have a floating lid to
reduce headspace. Remember this so called "scientific approach" can only
take the product so far.

Stan Kailis
Australia
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