One of the many questions I am asked by family and friends is about freezing olive oil, such as: what are the clouds in my olive oil, will olive oil freeze in the refrigerator, is freezing olive oil good or bad for it, and does the way it freezes say anything about its quality? So I will attempt to clarify these doubts. In Spain however, nobody really considers freezing olive oil it is always kept at room temperature but on ocasions in colder climates you may see changes in the appearance of your oil if temperatures drop others may mix olive oil with fresh herbs and then freeze them so the herbs don't deteriorate the oil.
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Most manufacturers preset refrigerator temperatures to around 2.5ºC. Chemistry texts list the freezing point of pure oleic acid at around 3.5ºC. Olive oil manufacturers don't generally list a freezing temperature because it is quite variable depending on the olive variety and ripeness of the olive at processing. Unlike the properties of an element or simple compound like water, olive oil is made up of hundreds of chemicals, many of which change with every extraction.
Like most fruit, olives have waxes in and on their epidermis (outer sking) to protect them from insects, desiccation, and the elements. These natural waxes are what allow an apple to be shined, for instance. If an oil is sent to a cold climate, or if it will be used in a product like salad dressing where it will be stored in the refrigerator, it is often "winterised" (chilled and filtered) to remove the waxes and stearates. A standard test to determine if olive oil has been winterized is to put it in an ice water bath (0ºC) for 5 hours. No clouding or crystals should occur.
Oil that has not been winterised will congeal 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 that produce long thin crystals, others form waxes that congeal into rosettes, slimy clumps, clouds, a swirl of egg white like material, or white sediment that the consumer may fear represents spoilage. These visual imperfections also may form outside the refrigerator during the winter when oil is exposed to cold temperatures during transport. The white color in the hardened oil does not indicate spoilage.
Chilling or freezing olive oil does not harm it, and the oil will return to its normal consistency when it is warmed. The ideal temperature to store olive oil to reduce oxidation but to avoid clouding is around 10°C. However you should only freeze it once, if you have to. Although I don’t recommend it as organoleptic properties will be affected.
To determine the actual freezing temperature, Dr. John Deane put several oils in the freezer with a thermometer. At 4.5°, most of the oils had not hardened or formed any crystals. At 1.5°C, most were firm enough that they could not be poured but were as soft as butter at room temperature. As the temperature lowered, more components of the oil solidified. At -12ºC, the oils were hard enough that a fork could not penetrate them. Determining at what point to call the oil "frozen" is a matter of semantics. This slow increase in hardening as the temperature is lowered is in sharp contrast to a pure substance such as water that switches from a liquid to solid phase at an exact temperature.
There is a rumor that true extra virgin olive oil, placed in a small quantity in a glass bowl and refrigerated for a while, would go cloudy and solidify in crystals, proving it to be extra virgin. A chemically refined olive oil, with a Little extra virgin however, would stay clear and eventually solidify into a solid block.
This is not a valid observation. While refined or pomace oils will usually be stripped of their waxes, thus making them more likely to form a block at very low temperatures and stay crystalline clear, and while it is more common for a refined oil to be winterised to be used in a cheap dressing, many excellent extra virgin oils do not form "crystals". Many premium oils will form a solid block when frozen. Unfortunately, detecting fraud is more difficult than just freezing the oil. It will depend on the variety and the wax content of the oil. It might give an orientation to the fact that it isn’t refined, if it goes cloudy but it will not detetermine that it is EXTRA VIRGIN, lampante oilve oil turns cloudy and aswell and that’s the oil that needs to be refined. So this is not a conclusive test by any means.
Many also think that the Fact that Olive Oil hardens in the refrigerator means that it is saturated.
Olive oil is not a saturated fat. All fats will harden if they get cold enough, whether they are saturated or not. As we saw above, olive oil often hardens, but not because it is saturated. It has not been refined as seed oils have been, to remove waxes. The presence of waxes does not make the olive oil saturated or unhealthy, it just means it is a natural product.
As a general rule, the more saturated the fat, the more likely it will be hard at room temperature. Beef and pork lard, margarine, butter, and the saturated tropical fats in cookies, packaged foods, and snack foods are all solid at room temperature. This improves their shelf life, makes packaging easier, and improves "mouth feel" but is not necessarily good for your health.
So my word of advice is, if for what ever reason you have to freeze olive oil (I can’t imagine why) only do it once, do not re-freeze it as it will affect the oil and deteriorate.