Does Olive Oil go bad?

Twice a year my neighbours go on a day trip to Calais, France, they hire a van, a rather big van, so big you could probably stage a moon landing in it. They go on this trip twice a year to do what they call, stocking up on essentials, in reality what happens is this; Mr Neighbour will fill the van with enough cut-price Red Wine to float a cruise liner, while Mrs Neighbour will buy enough cheese to feed a small nation for a month.

Yesterday, on their return from Calais, Mrs Neighbour surprised me with a new acquisition. She still had her cheese mountain, but on this trip she had also purchased 48 bottles of Olive Oil. After showing me her bounty of Olive Oil she posed a question, Does Olive Oil go bad? Now, I won’t lie to you, my first thought was to return her question with a question of my own, wouldn’t it have been a good idea to find that out before buying 48 bottles of the stuff? I didn’t ask that question though, instead I told her what I knew about Olive Oil, and as Olive Oil is a vital ingredient in salad dressings, I’m going to tell you too.

Yes, Olive Oil can go bad, rancid even. Olive Oil goes bad because of a process called oxidation, this process happens when air reacts with chemicals in the oil and produces peroxides. Now, while these peroxides can do wonders turning a brunette into a blonde, they do nothing to enhance the taste of a killer salad. The oxidation process speeds up when the Olive oil is exposed to air, heat and light. So you need to keep Olive oil in a cool, dark place, and in an airtight container. A cupboard is fine, and if you can keep you oil in a coloured container, not clear glass, it will be even better.

Now, even if Mrs neighbour takes my advice and keeps her Olive oil in suitable conditions, if she doesn’t get through her 48 bottles in under 3 years or so, it will eventually turn rancid anyway, due to auto-oxidation. Even in a cool dry place, in an airtight container, the antioxidants in the oil can only keep the auto-oxidation process at bay for so long.

So, my top tips for top quality salad dressings is to buy Olive oil as you need it, keep it in a coloured, airtight container, and keep it in a cool, dark place when you are not using it.