Why Do Olive Oil Tasters Use Blue Glasses?
The blue glass used in professional olive oil tasting is not decorative. Its color has a specific purpose: prevent the taster from seeing the color of the oil.
Color is a visual characteristic, not a criterion used to determine the sensory grade of virgin olive oil. Yet seeing a vivid green or golden oil can create expectations before the sample is even smelled.
The blue glass removes that information from the evaluation.
Why Hide the Color of Olive Oil?
People naturally make judgments from appearance. Olive oil is no exception.
A deep green oil may look young, intense or particularly fresh. A pale yellow oil may create a completely different expectation. Neither appearance establishes what the taster will actually find in the glass.
Professional sensory evaluation therefore attempts to prevent color from influencing the assessment.
Color bias, the influence that visual appearance can have on sensory expectations, is precisely what the colored tasting glass is designed to reduce.
A green oil is not automatically better than a golden one. Cultivar, fruit maturity and other factors can affect appearance without determining whether an oil satisfies the sensory requirements of the extra virgin category.
Why Is the Glass Blue?
The International Olive Council maintains a standard for the glass used in the organoleptic assessment of virgin olive oil.
The glass is dark-colored so the taster cannot evaluate the oil visually. The objective is not to make the oil look blue. It is to make its actual color difficult to determine.
This is part of a broader effort to control information that could influence sensory judgment.
As explained in What Is Blind Olive Oil Tasting?, professional blind evaluation conceals the identity of the sample. The colored glass removes another potential source of expectation: appearance.
The blue glass does not help tasters see something in the oil. It is designed to stop them from seeing something: its color.
Why Does the Tasting Glass Have That Shape?
The color is only one part of the design.
A professional olive-oil tasting glass has a wider body and a narrower opening. This shape helps retain and concentrate the volatile compounds released by the oil so they can be evaluated through smell.
Volatile compounds, molecules capable of entering the air above the sample and contributing to aroma, are an important part of sensory perception.
The shape also allows the taster to hold the glass comfortably while warming the sample.
The glass is therefore not simply a blue version of an ordinary drinking glass. Its form, dimensions and presentation are part of a standardized sensory procedure.
Why Is the Glass Covered?
Before the oil is smelled, the tasting glass is covered.
The cover helps retain the volatile aromatic compounds in the space above the oil rather than allowing them to disperse into the room.
The taster gently warms the covered sample and then removes the cover immediately before smelling it.
This creates a more controlled presentation of the aroma than simply pouring oil into an open container and leaving it exposed.
It also explains why the first stage of professional olive-oil tasting happens with the nose rather than the mouth. Aroma provides essential information about both positive characteristics and possible sensory defects.
Why Is Olive Oil Warmed Before Tasting?
Temperature affects the release of aromatic compounds.
In standardized sensory assessment, the sample is brought to approximately 28°C, or about 82°F. Warming the oil makes its volatile aromatic compounds easier to perceive without excessively heating the sample.
This is why tasters often appear to cradle the glass in their hands before smelling it.
Milan Truffle's guide to tasting olive oil describes the same basic procedure for consumers: cover the glass, warm the sample, smell it and then taste it while paying attention to its sensory characteristics.
The professional glass makes those steps easier to perform consistently.
What Happens After the Cover Comes Off?
The taster first evaluates the aroma of the oil and then takes a small amount into the mouth.
Air is drawn through the oil to help distribute it and increase retronasal perception, the perception of aromatic compounds reaching the nasal cavity from the mouth.
The taster evaluates fruitiness, bitterness and pungency and looks for sensory defects that may affect the classification of the oil.
These characteristics cannot be established by looking through a clear glass.
Nor does the blue glass itself determine whether an oil is good or defective. It simply removes a visual cue that does not belong in the sensory judgment.
Do You Need a Blue Glass to Taste Olive Oil at Home?
No.
A consumer can learn a great deal about olive oil using a small clean glass. Covering it while warming the sample and concentrating on aroma and taste can reproduce some of the practical steps used during structured tasting.
But if the purpose is to compare oils without allowing appearance to influence expectations, the oil's color should be concealed.
An opaque container or another method of blocking the view can accomplish that basic purpose in an informal tasting.
That still does not turn a home tasting into an official sensory panel. Professional assessment depends on standardized conditions, trained tasters and statistical interpretation of their evaluations.
The Glass Removes Information
The blue tasting glass is a small piece of equipment built around a larger principle.
Brand, price, packaging and reputation can influence expectations. So can color.
Professional sensory evaluation attempts to separate those expectations from what the taster actually smells and tastes.
The color of olive oil can influence the taster. The color of the glass is designed to prevent it from doing so.
The glass does not establish quality. It creates better conditions for the oil itself to be evaluated.