This is the first of a short series explaining the common chemical analyses applied to extra virgin olive oil. I’ll start off with the most universal analysis of them all – “Free fatty Acidity” – or known to most of us as ‘Acidity’.
Name: Free Fatty Acidity or FFA
Better known as: ‘Free Acidity’ or simply ‘Acidity’
What does it measure?: The level of breakdown of the fats in extra virgin olive oil.
Analysis debuted: Circa 1890
Use by olive oil producers: Universal
Degree of difficulty: Easy. Can be done using basic lab equipment and little technical expertise. You can see me conducting an FFA analysis here
Official Iimit for extra virgin status: < 0.8%
Unofficial limit strived for by good EVOO producers: <0.2%
Direct effects of high readings of FFA:
- Lower smoke point (the temperature at which the oil starts to smoke when heated)
- Greasy mouth-feel/aftertaste
- Shorter shelf life
Typical indirect effects of high FFA:
- Reduced positive flavours and/or greater defective fermented like flavours.
Common causes of high FFA:
- Delays between harvesting and processing.
- Diseased/damaged olives particularly due to olive fly infestation and anthracnose (fungus).
- Bruising of olives during harvesting followed by processing delays.
- Olives harvested from the ground.
- Frozen/frosted olives.
What is Free Fatty Acidity?
Every fat molecules including that in olive oil is comprises 3 smaller parts called fatty acids that are connected together. Figure 1 is the typical fat molecule found in olive oil – three monounsaturated fatty acids called oleic acid linked together.
Figure 1: Extra Virgin Olive Oil Nirvana. A perfectly formed and intact fat typical of olive oil.
However, having 100% perfectly intact fats like those shown in Figure 1 molecules is “fat Nirvana”. Sort of like that place that the “Watchtower” magazines portray – where humans live in perfect harmony with dopey lions and really small monkeys (both of which are likely to kill you at any given moment, but somehow reassuringly, for different reasons). But, getting back to the point, extra virgin olive oil is a natural product, and therefore is less than perfect. Individual fatty acids can be chopped off the fat molecule if the olives are riddled with fungussy olive pestilence, are being gouged upon by olive fly maggots, bruised and battered during harvesting, or (more typically, and less dramatically) if the olives are left to even slightly decay in the interim between olive harvest and processing.
Figure 2: Formation of free fatty acids. The Pacman represents a lipase enzyme, but if you like, you can think of it as a Pacman.
Nature has devised a few ways of busting up intact fat molecules to form free (aka single) fatty acids. Her chopping utensil of choice are enzymes called lipases. They are found in the olive fruit, but in good fresh undamaged olives the lipases are harmlessly locked up in the olive cell away from the fat molecules that they desperately want to destroy. But when the olive cells are damaged in any way, the enzymes are able to escape from their compartments, and in frenzied attacks dismember the intact fat molecules freeing up fatty acid molecules (Figure 2). The more diseased the olive, or the longer the time gap between olive harvesting and processing, the more enzymatic activity and the higher the free fatty acidity.
Common misinterpretations/misrepresentations of FFA in olive oils.
“FFA is a good indicator of olive oil quality” – Sort of right.
Free fatty acidity is widely acknowledged as a good index of general olive oil quality. While this is generally true, I have tasted many examples of higher FFA extra virgin olive oils that taste just fine, and conversely I have tasted many low FFA oils that are woefully defective. Take for example what is possibly the worst tasting defect in olive oil called muddy sediment. It has a foul (for olive oil) taste of parmesan cheese, baby vomit, salami, band-aids, horse stable and fetid milk (and combinations of these). An olive oil can pick up these characters from short term exposure to the particulate olive sediment that remains after oil extraction and which later falls to the bottom of a tank. The aroma compounds that contribute to this defect are very potent. Therefore whilst leaving the oil on the sediment may result in only a small break down of the fat (resulting in a small increase in FFA), this small increase in FFA can be accompanied by a large reduction in flavour quality.
“Refined olive oils have high FFA” – Very wrong!
Paradoxically nothing is further from the truth. Refined olive oils (i.e. those labelled as pure, light and ‘olive oil’ ) have essentially zero FFA. Yep, zero. The confusion probably arises from the fact that badly made olive oils, i.e. oils with very high FFA’s are those destined for refining in the first place. The major purpose of the refining process is to remove the free fatty acids. This is effectively acheived by adding caustic soda which converts the free fatty acids to soap which can then be physically removed from the oil.
“The FFA of an EVOO increases substantially during storage” – Wrong again.
The production of free fatty acids from intact fat molecules is process that mostly involves the action of enzymes found within the olive which act in the presence of water. Once an olive oil has been properly extracted from the olive and most of the water has been removed (<0.1% remaining), further degradation in bottle leading to higher FFA is very unlikely. Typically, a properly processed EVOO with a low FFA of 0.2% at the time of processing, may get up to between 0.22% and 0.25% after 12 months of storage. Ok, that’s a 10-20% increase, but when you consider that your typical inexpensive supermarket purchased EVOO from the EU typically starts at 0.60-0.80% the 0.02-0.05 increase in FFA due to storage is inconsequential.
“You can’t taste acidity in olive oil” – Got that one right.
The free fatty acids are so weak that they don’t have the ability to bother our otherwise very busy acid taste receptors.
“If the FFA of an olive oil is X% measured as oleic acid , this mean that the olive oil contains X% oleic acid”. – NO it does not mean that.
The “measured as oleic acid” is simply a unit of measurement. For a few anally retentive lipid chemists, it may seem important, but in reality, whichever fatty acid equivalent (pick one, any one), it really has bugger all effect on the final result. So everyone can ignore the “measured as” bit without any loss of meaning. That’s of course unless you are an anally retentive lipid chemist. But to satisfy the inevitable “% bi (oleic acid) curious” readers, I might have a go at explaining it in a forthcoming post.