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Dec 22, 2009 06:52 AM

frozen olive oil: still ok?

I had a couple bottles of olive oil delivered to me in the mail. Being winter, the contents had seen low temps for at least a day sitting outside and were completely frozen through. Just wondering if it's as good as new after thawing or whether it loses anything after?

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  1. Nothing lost in hardening, but make sure to give it time to return to liquid and settle back to a homogenous mixture. There are a lot of different oils in olive (or any vegetable) oil, and they harden at different temperatures, causing them to seperate out. If you start using it before it's thoroughly returned to liquid and had a chance to recombine, it can taste off.

    4 Replies
    1. re: danieljdwyer

      Daniel, I'm interested in exploring this topic further, can you expound on the different oils in your olive oil remark? Serious inquiry.

      Olive Oil is a complex compound made of fatty acids, vitamins, volatile components, water soluble components and microscopic bits of olive. Primary fatty acids are oleic and linoleic acid with a small amount of linolenic acid. Is this what you're referring to? I thought it was primarily the waxes in the olive oil that crystallize into a slurry when the oil is chilled:
      "Oil which has not been winterized will clump and form needle-like crystals at refrigerator temperatures as the longer chain fats and waxes in the oil congeal, but the oil will not usually harden completely unless chilled further. Some olive varieties form waxes which produce long thin crystals, others form waxes which congeal into rosettes, slimy clumps, clouds, a swirl of egg white like material, or white sediment which the consumer may fear represents spoilage. These visual imperfections may form outside the refrigerator during the winter when oil is exposed to cold temperatures during transport. Chilling or freezing olive oil does no harm and the oil will return to its normal consistency when warmed."

      BTW, I keep my olive oil in the frig, which greatly extends it's shelf life. It does cloud when chilled but clears quickly upon reaching room temp.

      1. re: bushwickgirl

        Yes, that's more or less what I'm referring to. There are, however, only very small amounts of free fatty acids in olive oil (I believe this is generally true of fats and oils produced by all living things). Most of the volume of olive oil is composed of glycerides (fatty acid chains bonded to glycerin), mostly diglycerides and triglycerides.
        When I said "different oils" I suppose it would have been more correct to say lipids. There are many different lipids in olive oil, including the free fatty acids, glycerides, free glycerol, sterols, vitamins, phospholipids (though I believe these are all isolated in the olive cellular matter so do not mix directly with the other lipids), and probably some others I don't know about (maybe phenols or other hydroxyls).
        Even if we just consider the two main fatty acids (oleic and linoleic) in their two main forms in the oil (diglyceride and triglyceride) that's four different fats. Each of these four, along with the dozens of minor fats and lipids, will solidify, or freeze, at a different temperature. Even though the variation can be as minor as a fraction of a degree, this will cause the form of the mixture to change and the various component lipids to separate from each other.
        They will thoroughly remix fairly quickly at room temperature, and no damage is done. I do see people that don't wait for this to happen though. A natural olive oil based salad dressing will solidify in the referigerator (or the olive oil will, at least), and I've seen people take these out of the refrigerator run the bottle under warm tap water for a few seconds so that some or even most of the oil liquifies, give it a shake, and pour. If there are still solids remaining, the composition has changed (and by pouring some out while some remains solid, you've permanently altered the composition).
        This does affect the scent and flavor, and can do so to either a large or small degree. I did a little experiment once where I took a small bottle of olive oil and poured some out into a small dish, then refrigerated the bottle until it was solid. I then took it out and let it sit to liquify, pouring some out into a separate dish each time a small amount had liquefied, so that by the time the whole bottle was back to liquid I had six dishes of olive oil. They all tasted different, and the first two tasted absolutely terrible. The last one was sort of flat tasting, so I'm assuming those first two got most of the strong flavor compounds.
        I believe in the quoted text that waxes refers to the glycerides. Wax, oil, and fat are terms that are commonly used in a very inexact way. Oil could technically refer to any hydrophobic liquid, and wax could refer to any hydrophobic solid.

        1. re: danieljdwyer

          OK, thanks for your reply.
          The wax esters, which are glycerides, occur on the epidemis of the olive, to protect the olive from insects and desiccation. Oil producers will "winter" the oil, that is, solidify the oil by chilling, then straining out the waxes and stearates. Oil that hasn't been winterized will clump, as I noted in my post upthread.
          As far as the wax being a hydrophobic solid, I agree that it is.
          Interesting experiment. I will mention it to friends that routinely keep olive oil in the frig.

          1. re: danieljdwyer

            Thanks, danieljdwyer, for the exhaustive lesson in fats, waxes and oils.

            I've never stored olive oil in the refrigerator, but I store the dressings/sauces that I make with it in the fridge. I've always been hesitant to use them until *every last bit* of the whitish solids have melted. Now I know my efforts ("thawing" under warm running water, microwaves) weren't in vain!

            Thanks also for assuring us that although the oils and waxes in olive oil separate under refrigeration, they will thoroughly remix at room temp. I've *used* olive oil that had been refrigerated (but brought to room temp) when visiting others' kitchens, and didn't detect a taste or textural difference from the non-refrigerated product.

            EDIT TO ADD: I've been thinking about this... a "trivia" question that will disclose my alarming unfamiliarity with "exotic" oils (if one considers olive oil exotic any longer): are there other food oils (e.g., grapeseed etc.) that separate this way? Does refrigerate do more harm to them than to olive oil?

            I also make herb- and garlic/hot peper-infused olive oils that I give as gifts in nice bottles. I'm certain that some of the recipients refrigerate the stuff. When the oil separates, I wonder if it's the resulting oil, or the wax, that holds all the good (oil-soluble) flavors?