We’re frequently asked if we filter our oils. This question often comes from reading some faulty information on the internet or thinking olive oil is somehow similar to apple juice in this regard.
We filter our oils with mechanical means – meaning there is no chemical reaction. The newly milled oils are just passed through very fine meshes and a special felted paper designed specifically for trapping the olive particles and juices. Based on the recommendations of Marco Mugelli, the pioneer of naturally preserving olive oil polyphenols, we do this in-line, immediately after the oil is extracted and before it is pumped into a tank. This way, almost no sediment remains and there’s no chance anaerobic decomposition of the sediment will produce off smells during storage. Once spoilage begins to happen, other chemical processes kick in that rapidly lead to oxidation, rancidity, and unpleasant smells and tastes.
Some people centrifuge their oil to remove particulate matter, but this method introduces a lot of oxygen which reacts with the antioxidants in the oil. We also used this method early on, but we found that our oils lost their freshness due to the excessive oxidation much more quickly.
Others rack their oils the old-fashioned way to remove the vegetable water and particulate matter. After a cloudy oil has been in a tank for days or weeks, the sediment will have settled to the bottom, and then the clear oil is pumped into another container. We used to use this method early on as well and found the same problem with the freshness not lasting as long as we wanted.
Some olive oils are sold as “unfiltered”, conjuring up the benefits of unfiltered apple juice – as though this was a positive aspect in olive oil; it is not. The difference is that fresh, unfiltered apple juice is consumed almost immediately, whereas extra virgin olive oil, even though it is also a fresh product, is supposed to last for about two years. Particles suspended in olive oil usually begin anaerobic spoilage within a month or two, which is also one reason we never put herbs or other things into our oils.
Two years ago we had the polyphenol levels analyzed twice – as soon as the oils were made and again after the summer, 8 months later. We found, to our surprise, that the levels hadn’t changed a bit! Our oils are very stable because we take every precaution to avoid oxidation and prevent spoilage. We’re confident that immediate mechanical filtering is one of the keys to the exceptionally high polyphenols, and beautiful award-winning aromas and flavors – as well as the long shelf life of our oils.