The simplest way to understand the different tastes of virgin olive oils and the way to evaluate them is to compare an oil of low quality with one of high quality. It is very important to be able to recognize a bad oil, as many people have only tasted bad oil and think that this is how a good oil should taste. The basic procedure is straightforward.
Pour a small quantity of oil into a small glass or even a plastic coffee cup. Warm the contents in the palms of your hands to free the volatile aromas so that they can be detected. Bring the cup to your nose and inhale slowly two or three times.
Memorise the sensation (or make a written note) and, if necessary, repeat after a minute or so. Now you have completed the olfactory test.
Next comes the taste-tactile test. Take a tiny amount of oil in the front part of your mouth, move it around. Take repeated short sharp breaths, bringing air into your mouth through your clenched teeth and blowing the air out through your nose. This allows you to confirm the intensity of the volatile components identified earlier during the olfactory test.
The last stage is really an extension of the previous one. Transfer the oil into the back of your mouth and upper throat ( it doesn’t matter if you swallow it – unless it is really bad oil). This will allow you to gauge the viscosity of the oil and to identify other flavours and characteristics. In particular, the bitter and the peppery tastes that are typical of Tuscan olive oils should be very evident.
If necessary, repeat the process, but only after having rinsed out your mouth (or cleansed it with bread or, better, apple). The stronger the taste of the oil, the longer you should wait between tastings.
Only at the end should you look at the colour, to avoid any possible bias. Ideally, the tasting glasses should be opaque.
The Meaning of Some Analyses
When you look at a line of bottles of extra virgin olive oil on a supermarket shelf, it can be useful for you to take a look at the label on the back that lists some of the important analyses that are required in the USA. These are some examples.
- The acidity determines the classification or marketing category of the oil.
- The tocopherols indicate the content of Vitamin E. They are an index of the quality of the oil and act as antioxidants, i.e., they protect the oil from ageing. They also have a high nutritional value.
- The polyphenols play a part in the taste of the oil and these too are protectors, acting as antioxidants. They also have a high nutritional value in the human diet.
- The peroxides indicate the state of conservation of the oil with specific reference to rancidity. The lower the number of peroxides, the better the quality of the oil.
- The spectral UV analysis enables you to distinguish an oil that has been ‘pressed’ from one that has been produced by chemical means, as well as the state of oxidation. Industrially produced oils have high K and Delta K (∆K) values.