How tasters taste oil: small glasses, warmth, and the cough

Olive oil has a written international method for how to taste it, from the shape of the glass to the hour of the day. The method comes from the International Olive Council, and trained panels use it to decide what grade an oil earns. You will never need the booth or the paperwork. The reasons behind each step are still useful, and most carry over to a kitchen table.

The glass and why you cannot see the oil

Each taster gets a covered glass holding 14 to 16 ml of oil, which is about a tablespoon. The glass standard describes a squat, steady shape about 60 mm tall, with a mouth narrower than its body to concentrate the smell. A small lid called a watch-glass sits on top to hold in the aroma and keep out dust.

The color of that glass is the part people remember. The standard calls for dark glass so the taster cannot see the oil and judge it by its looks. The California Olive Oil Council describes these glasses as blue and says the color of an oil tells you nothing about its quality or flavor. Each sample also carries a random code. Only the panel leader knows which oil is which, so tasters judge what is in the glass. At home you can relax about this. The Council's own guide for consumer tastings allows clear cups in informal settings. It treats the greens and yellows as part of the pleasure.

Why the oil is warmed

Temperature gets its own clause in the method, with samples held at 28°C, give or take 2 degrees, for the whole test. The method says differences between oils are easier to spot at that heat than at room temperature. Below it the aromas rise poorly. Above it the oil starts to form the volatile compounds of heated oil. Each booth has an aluminium block in a thermostatic water bath to hold that heat.

At home, your hand can do the job of that heating block. The California Olive Oil Council suggests covering the glass and letting it warm in your hand toward 82°F. A University of Arkansas tasting handout suggests holding the cup for about 20 seconds, then smelling again to notice what has changed.

Smell first, then the slow sip

Once the oil is warm, the steps run in a set order, and it is easy to follow them yourself.

• Tilt and turn the covered glass so the oil wets the inside.
• Uncover it and smell. The official method asks for slow, deep breaths for no more than 30 seconds, then a short rest if you have not decided. The California council describes a quick inhale from the rim, so try both.
• Take a small sip, around 3 ml in the method. Move it through the whole mouth and very slowly over the back of the tongue toward the throat.
• Draw in short breaths of air through your mouth. This spreads the oil and carries its aromas up the back of the nose. The California council calls this the slurp.
• Swallow a little and wait for the throat to respond.

The slow part of that sip has a practical reason behind it. The method warns that if the oil is not spread slowly enough, bitterness and pungency can both go unnoticed. Pungency can also cover up bitterness. Tasters concentrate on the order in which the two arrive. Bitterness registers on the tongue. The method calls it typical of oil from green olives or olives turning color.

What the cough means

Coughing is a known reaction. The method defines pungency as a biting sensation felt through the mouth and most of all in the throat. It lists pungency as a positive attribute, alongside fruitiness and bitterness. The California council notes that oils are sometimes called one or two coughers. NPR's report on the science took the scale as far as three.

Researchers have traced why the sensation lands where it does. In 2011, scientists at the Monell Chemical Senses Center reported on oleocanthal, a polyphenol in extra virgin oil. It activates a receptor called TRPA1, and that receptor sits at the back of the throat. The same release says connoisseurs treat the sting and the cough as signs of high quality. The official score sheet never mentions coughing. Tasters mark pungency on a 10 cm line along with everything else. The panel's median can then earn a label such as delicate or medium.

This is also why swallowing matters. The Arkansas handout has you roll the oil around without swallowing, which works for flavor. The California council says you must swallow at least a small amount to judge pungency. The official method calls swallowing advisable for the same reason. If you find the bite unpleasant, you have plenty of company. A UC Davis study of 110 Northern California olive oil consumers found that most disliked bitter and pungent oils. They did like fruitiness.

Keeping your palate fresh

Trained tasters guard their senses before they sit down. The method asks them to avoid smoking and coffee for at least 30 minutes and to fast for an hour. They wear no fragrance and work in silence. It recommends tasting between 10 in the morning and noon. Sensitivity rises before a meal and falls after one.

The limits on quantity are easy to borrow. Panels assess at most four samples in a session. The Arkansas handout suggests three or four at home so your palate is not overwhelmed. Between oils, the method recommends chewing a small slice of apple, spitting it out and rinsing with a little water. It leaves at least 15 minutes between sessions.