While cleaning out your kitchen cupboards, you discover (with horror!) a bottle of olive oil with a best-before date that has long passed. At the price you paid for it, would you like to know if it's still good? This article is for you!
What is rancidity?
If oil goes rancid, it's due to the progressive oxidation of its fatty acids. This means that the fatty acids break down when the oil comes into contact with oxygen in the air. Rancidity leads to a deterioration in odour and certain nutritional properties.
Oils and fats are more likely to go rancid if exposed to:
- Heat
- Oxygen
- The light
- The passage of time
Nuts and whole-grain cereal products, such as brown rice and whole-wheat flour, become rancid easily, as they also contain essential fatty acids.
Is rancidity dangerous?
According to the Canadian Food Inspection Agency, rancid foods may cause minor digestive discomfort but don’t represent a health risk. This doesn't mean you want to keep rancid food. A very rancid ingredient is naturally repulsive to humans in taste and smell.
The bad news is that many foods on the market possess a certain rancidity. Many people figure that it happens and accept it. It’s just the way it is. This is particularly true of oatmeal and its derivatives (granola bars, etc.).
Buying very large oil formats (apart from our BIB format, where the bag collapses to keep oxygen out) to save money also means you can gradually expose yourself to potential rancidity without realizing that you're getting used to its shortcomings.
Signs of rancidity in oil
So how can you tell if your oil is rancid? Use your nose!
If it smells good (vegetal, fruity, citrus), it's probably still good. On the other hand, if your oil smells unpleasant, there's no reason to put it in your dishes. It will ruin them!
Rancid olive oil can smell like:
- Wax crayons
- Paints, solvents and varnishes
- Glue
Rarely is rancidity the only problem with oil. You may notice other odours: vinegar, overripe fruit, dampness, mildew and dust. If it smells bad, it probably is bad.
The bitter myth
Have you ever heard it said that rancid olive oil tastes bitter? It couldn't be further from the truth.
A good-quality extra virgin olive oil (and to qualify as “extra”) must be bitter when fresh. The bitterness comes from polyphenols and other antioxidant compounds, which play a protective role against oxidation, and, therefore, rancidity of the oil.
Less bitter olive oil may actually go rancid more quickly!
The moral of the story: if your oil still smells good, even after its best-before date, it's still good to enjoy!