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I have bought a 5l container of olive oil which is impractical for daily use. I intend to decant it into something smaller but I'm not sure what to buy.
I know that olive oil is affected by light and temperature. However particularly on light I don't know whether a green bottle is enough or is it better to block all light? How long does it take for light to spoil it?
From my research on this, it sounds like you should be minimising the following as much as possible (two of which you've mentioned in your question):
To avoid this, it sounds like the best option is a fully opaque, thick-walled vessel, that is sealable. This article on the Kitchn recommends a ceramic cruet, which seems like a sensible choice, but sounds like anything along these lines would work. So if I had the choice between tinted or attempting to block all light, I'd block all light.
Even storing in these conditions, most of what I've seen says it is ideal to consume within approximately 3 months of opening (some sources say a little less, like that Kitchn article which quotes 1 month, and some say a little longer - around 6 months) - though unopened oil should keep for about a year or 2. I don't know that it's possible to say how much more quickly the oil would go rancid in a clear container, however, I think leaving it out for 6+ months will have an impact on flavour.
Get a darkened glass bottle - can be dark green or amber-colored. Amber-colored filters out better than green, it is easier to recycle and produce (therefore, cheaper), that's why we very regularly use them in pharmaceuticals.
The most important things for you to focus on, though, are temperature and oxygen. Your bottle must have a well-fitting cap, bung, or cork and you need to fill it with the least headspace possible. After filling, keep it in a cool and dark place, like a pantry or cabinet that doesn't go very frequently or for extended periods above 27-30C
If stored correctly, your oil should be good for around 2 years. It might still be usable after this, but you need to check for oxidation after opening
Let me state a premise.
You can preserve olive oil in the original, sealed, metal can for years without much harm, if stored in a cool place (between about 5°C and 15°C) with few temperature variations.
I did it for years with extra-virgin (EV) olive oil. The only problem is that the oil will lose many micro-nutrients (especially vitamins) and some of its organoleptic properties (less tasty). However, it will still be good and have a fine taste nonetheless.
Now to the point.
The worst enemies of olive oil in day to day use are light, temperature variations (and high ambient temperature) and air ingress in the container.
As for light, a very dark green glass bottle is enough if you keep it in a closet where light can't enter. Depending on how much oil you consume, you should consume it all in a couple of months, before refilling.
Always clean the bottle with very hot water and heavy shaking and let it dry before refilling. You could (I don't) use a drop of dish soap to clean the residue from the bottle, but you must be sure to wash away all the soap residue very thoroughly.
Refilling a bottle from the can with new oil before the "old" is not finished may increase the chance it goes rancid. So avoid that, especially if a bottle (1 liter) of oil lasts you more than a month. In this case it's probably better to use a smaller bottle for everyday use.
If storing the bottle in a closet is unfeasible or impractical, you can improve its resistance against light by wrapping it with aluminium foil. Some very high quality EV olive oil is sold here in Italy with bottles that are already wrapped in alufoil.
It is better to keep the bottle tightly closed with an airtight cap. However this is somewhat impractical. If you use a small bottle, you could afford some kind of "beak-caps", which let you pour oil in minimal quantities and still keep the bottle closed (but not airtight).
This is an example:
Since you asked for some numerical data, I give you those from my direct experience. I get EV oil in 5L metal cans. Once opened, I keep the can in my apartment pantry, which is not particularly cool (26-28°C in Summer), for about 6-7 months. It's not ideal, but the oil never got bad.
I use the can to refill a small, very dark green bottle (500ml) with a "beak-cap" similar to the photo I posted, which I keep near my kitchen table, so not inside a closet, but not in direct sunlight. I perform a refill about once every 2-3 weeks.
The setup is not optimal, but it is convenient and practical. Never had any kind of problem: no rancid oil, no bad taste, no lessening of the taste or perfume of the oil.
Note: I've been exclusively using EV olive oil for my entire life, and so my mother's family (my granddad was in the olive oil business). By exclusively I mean, the only fat used for cooking, frying or dressing, with the very rare exception of the occasional butter.
It's a very expensive product, but it's worth any drop of it. It's probably the best edible fat under any aspect. The ancient called them "the green gold" and sometimes you here that expression still used here in Italy from people knowledgeable in the field.
Beware, though, that you should buy EV olive oil, not plain olive oil or other olive oil products which are not marked "extra-virgin", which are far inferior products.
Be also aware that there are lots of fake products, especially some fake "made in Italy" ones. They dilute normal (non EV) olive oil with other kind of oils and if the color doesn't end up resembling that of a variety EV olive oil they add up colorants (e.g. chlorophyll).
High quality "made in Italy" EV olive oil (made with Italian olives) is quite expensive. You won't find any under about 8-10 EUR per liter (retail) here in Italy. Anything under much lower than that price is highly suspicious.
Even if it's not fake, it may be "made in Italy" but using olives coming from abroad, or it may be EV oil only bottled in Italy. If you are lucky, you get a fine product anyway, although not high quality (e.g. it would have less good properties, taste not exceptional or be more prone to go rancid). Otherwise you may end up getting some real crap, although you may be unable to tell the difference by just tasting it, unless you are a bit of connoisseur.
EDIT
After some research prompted by comments in the whole thread, I found a very interesting PhD thesis about olive oil, that in part address the storage question.
For further reference, here is the link to the portal of the university relative to that thesis.
I had the same problem. Here's how I solved it. First, I distribute 5 L of olive oil into a bunch of mason jars. Second, I put them in the fridge. It is a dark place, and the oil preserves well there. In my experience, it tastes great for at least a year after I do this.
Interestingly, it congeals while refrigerated. That's why I use a spoon to scoop out when I need to use it. It melts very quickly.
Summary: a wine bottle and a matching vacuum pump (and/or marbles).
Wine has many of the same issues with storage. I occasionally enjoy a good dry red, but that is infrequently and only about half a glass at a time. What to do with the opened bottle?
So I can drink from a bottle for around 6-8 weeks. Yes, oxidation does start to affect the wine, but much less than if it were simply stoppered up. And some wines do well with a little bit of "breathing", so it has never bothered me.
Another way to displace air from a container is to drop in (clean) marbles (the spherical glass toys - does one still get them?) to take up the space of the decanted liquid, then stopper up. This is actually done to store e.g. opened champagne for a few days, as the vacuum pump would "suck out" all the bubbly otherwise. (Seems like a bit of a chore to clean up the marbles after use, though...)
What colour wine bottle? This is my experience with a single datapoint (anecdote, so take with the necessary pinch of salt). I was interested in reusing the same empty wine bottles in a "passive solar water wall" (use your favourite search engine if you want to find out more about the concept). However, I was concerned with algae growing in them - the wall should be exposed to as much sunlight as possible, but sunlight fuels the growth of algae (as seen in white plastic bottles I use as a drinker for backyard chickens). So for my experiment I took the lightest-coloured green wine bottle I had available, filled it with plain tap water, and stoppered it up with a cork wrapped in plastic food wrap (to get a somewhat more air-tight seal). This I placed in an equator-facing window, which gets full sun throughout the day. After a year there was still no algae growth, no specks floating in the water, and the water did not smell "off" (not very scientific, I know). So I think any handy coloured wine bottle would be just fine to protect against light (as others have stated, you could always wrap it in some opaque material and/or store it in a cupboard).
When shopping large quantities of olive oil for regular household use I would recommend to go for a brand that is using bag-in-box packaging instead of the common tin containers as this allows to dispense oil as required while avoiding oxygen contact of the stocked part entirely.
For many years, I did the same as what my mother did— I kept a smaller bottle sold for olive oil, and refilled it from a large can of olive oil.
The reason is, it has the little plastic insert in the bottle so it doesn’t pour too quickly, and it’s a dark green glass, to prevent the light issues. (But I keep it in a cabinet, so it’s only out in the light when I’m using it)
I never worried about the can of oil. I takes me about a year to go through it, but I’ve never noticed any adverse taste to it in that time.
Many years ago, I got an olive oil dispenser like Alton Brown used on Good Eats. It’s a stainless steel cylinder with a flip lid that you activate with your thumb, and there’s a plastic insert with a pour spout. (It looks like this, but I don’t think that’s the same brand) I love it, but a word of caution— if you overfill it, the oil will push enough to eject the whole plastic insert. I move my thumb to the plastic insert when pouring.
