The Nose – olfactory sensations
The aroma of olive oil reveals a great deal about the quality and origin of the oil. The gas molecules, the volatiles, given off by an oil react with the nerve receptors in the inner surface of the nose, the epithelium. Certain molecules fit into these receptor sites better than others and the collection of ‘fits’ gives us the complex aroma of the olive oil. We can detect the molecules that fit the receptors at relatively low concentrations.
To increase the volatility of the product, we heat it – as we do with olive oil we are about to taste by cupping it in our hands. This increases the number and range of gas molecules available for us to detect and describe as the aroma of the olive oil.
Our brain then uses our prior experience of the olfactory sensations to describe them – hence the oil might remind us of ripe tomatoes. Obviously the greater the range of aromas we have experienced – the greater the range of descriptions we will have available to us.
Over-exposure to one smell results in the saturation of receptor sites and reduces the influence of that aroma. It is best to take one or two sniffs and record your impressions – then come back to the sample later if you are undecided.
So I suggest we start smelling more and fixing the aromas in our ‘aroma vocabulary’. I find it takes a conscious effort to do this and continuous practice to refresh and expand the vocabulary.
The Eyes – visual sensations
When you take your olive oil to a restaurant and try to flog it to the chef – the first thing that happens is that he/she gets a white plate and pours the oil onto it. Colour and viscosity are important to chefs where the visual impact of a dish is extremely important and the ability to make emulsions with the oil a consideration.
Another visual influence if you are tasting oil in a market environment is the packaging of the oil. Poor packaging, or a brand you know from previous tasting, may well influence your assessment of the oil before you start the formal evaluation process.
Colour is not an indicator of the quality of an olive oil so in the evaluation of an oil for quality we eliminate the visual perceptions by blind tasting from blue or brown glasses made to an International Olive Council specification.
In a group tasting, the behaviour of other tasters can also influence your perception of the taste of an oil. Seeing a taster pulling a face after tasting can have a stronger influence on us than we may care to admit – depending on our opinion of that taster’s ability. So for professional assessment, tasting in isolation is advocated.
The Mouth – taste sensations
The sensory receptors in the mouth are stimulated by soluble substances that are not volatile. The receptors are concentrated in taste buds with the main function of detecting the primary elements – namely sweet, acid or sour, salty and bitter. The taste buds that detect the different primary elements are themselves concentrated in different parts of the mouth so the tastes are picked up at different stages of the tasting process.
The taste regions are as follows:
- Sweet – on the tip of the tongue
- Salt – upper edges of the tongue
- Sour/acid – side of the tongue
- Bitter – back of the tongue
To get the full benefit from all the taste buds it is important to coat the inside of your mouth with the food – in our case olive oil – and roll it around so the soluble elements can dissolve.
As the substance you are tasting spreads from the front to the back of the mouth you will detect sweetness first, then saltiness, followed by sourness and finally bitterness.
In olive oil there is no sugar or salt and the acid receptors are not stimulated by free fatty acids The bitter components in olive oil are soluble, the main one being oleuropein, and stimulate the relevant receptors.
The texture of the olive oil – or viscosity – also gives an impression known as mouthfeel.
When tasting extra virgin olive oil there is another tactile sensation at the back of the throat caused by the polyphenols irritating the mucous membranes and tactile follicles at the back of the throat. The sensation is described as pepper or piquancy. This is a chemesthetic sensation rather than taste. Chemesthetic is the combined response to cutaneous, thermal and painful stimuli caused by some chemical irritants. The membranes can become overstimulated fairly quickly with the result that oils tasted subsequently can be perceived as more piquant or peppery than they are.
The Ears – sound sensations
While olive oils don’t emit sound waves, humans do and the coughing caused by pepperiness or comments made by a taster can also influence the assessment of the taste of an olive oil.
A satisfied grunt, often involuntary, after the initial taste of an oil can also be a positive influence – albeit undesirable.
Hence we recommend silent tasting – and in a professional tasting, once again tasting in isolation.