Recently, a wine glass produced by a renowned Master of Wine (MW) was introduced in Japan, garnering considerable attention. This particular MW has consistently used the same glass for both red and white wines throughout many years of professional practice. Furthermore, this MW had long questioned the “conventional wisdom” that dictates using smaller glasses for white wines than for red wines, despite the fact that white wines can sometimes possess richer aromatic profiles than mediocre red wines. These experiences and doubts served as the impetus for producing this particular wine glass.
Size considerations aside, it is frequently noted in wine production facilities and tasting environments that changing the glass used can dramatically alter the expression of the same wine. This phenomenon has been empirically understood by many practitioners.
The question then arises: does the glass used actually change the taste of wine? If the taste does change, what is the underlying mechanism? This article will examine these questions in detail.
Does the Glass Used Actually Change the Taste of Wine?
To state the conclusion first, changing the wine glass used does not alter the intrinsic taste of the wine itself. The reason for this is that under normal usage conditions, changing the wine glass does not cause any chemical reaction between the glass and wine that would modify the wine’s “quality.”
On the other hand, there is sufficient possibility that changes may occur in how the taste of wine is “perceived.” Indeed, many individuals are believed to have experienced such changes.
Some may consider this a matter of semantics, but it is crucial to recognize that changing the wine glass alters the “perception” of taste rather than the “taste itself.” This distinction constitutes an absolutely necessary prerequisite when discussing the influence of glassware from a scientific perspective.
Wine “Taste” is Perceived Through All Five Senses
Not limited to wine, when humans perceive “taste” holistically, they do so not solely through gustation but through all five senses, including olfaction and vision. This fact can be understood through experiences such as drinking wine while pinching one’s nose or while blindfolded, which result in different taste perceptions.
Regarding wine taste, olfaction and vision—which perceive aroma and color, important elements constituting wine—tend to be considered the primary sensory organs beyond gustation. However, in reality, tactile sensation also plays a substantial role in perceiving wine taste.
Elements That Change When the Glass is Changed
Changing wine glasses is often understood as a straightforward relationship where the glass shape changes. Consequently, many people understand that glass shape influences how wine taste is perceived. However, in reality, another critical factor is involved in this relationship.
Changing the wine glass used brings about two distinct changes:
- The glass shape changes
- The glass material changes
Each of these elements will be examined in detail.
Influence of Glass Shape
To understand what influence wine glass shape has on wine taste perception, the most straightforward method is to examine the perspectives from which glass development is conducted.
Riedel is an extraordinarily renowned wine glass manufacturer, likely familiar to virtually everyone in the wine industry, specializing in developing wine glasses of diverse shapes. Under the policy that “glass shape is determined by the beverage’s character,” Riedel develops and markets wine glasses with optimal shapes for each grape variety.
Organizing the information presented on Riedel’s website reveals that the company emphasizes the following elements in development:
- Liquid volume
- Flow rate
- The point on the tongue where wine flows when taken into the mouth
- Aroma release methods and their maintenance
When the glass is changed, the size of the glass bowl changes. When bowl size changes, the surface area where the poured wine contacts air changes. When surface area changes, the volatilization volume and volatilization conditions of volatile compounds change. Therefore, it is a logical consequence that the aroma released within the glass changes.
Additionally, bowl shape determines whether the nose is completely covered by the glass. This consequently changes how the nose can actually detect the aromas present within the glass.
If the shape and condition of the bowl rim differ, the flow rate into the oral cavity changes. Furthermore, the point where wine flows in—whether toward the tip of the tongue or the posterior region—also changes. Therefore, these elements can also be said to significantly influence taste perception.
Although not directly mentioned on Riedel’s website, when glass shape changes, glass size naturally changes. Consequently, glass weight changes. Combined with liquid volume changes due to bowl size variations, changes in the glass’s own weight are actually one of the factors influencing human taste perception.
Regarding glass manufacturing methods, there exists a distinction between handmade and machine-made production. This distinction primarily produces significant differences in tactile sensation when holding the glass or placing it to one’s lips. This difference also constitutes a factor that greatly influences the taste, aroma, and impression experienced when drinking wine using that glass.
Changes in Shape That Are Easily Comparable
To organize at this point, the influences arising from changes in glass “shape” include the following elements:
- Liquid surface area
- Liquid volume
- Flow rate and position where wine flows in
- Volatilization conditions of volatile substances and their maintenance
- How aroma enters the nose
- Weight
It is extremely difficult to separately isolate and verify the changes these elements bring to taste perception. However, comparing the overall change is simple, as it merely requires changing the wine glass used.
One point requiring attention is that if the temperature of the wine poured into the glass changes, factors other than those related to the glass will be incorporated. Therefore, it is necessary to maintain constant wine temperature when comparing glasses.
Conversely, what is extremely difficult to compare in practice are changes resulting from differences in “material,” which will be discussed next.
Wine Glass Material
Not limited to wine glasses, the material of glasses is glass. However, this material called glass actually encompasses many varieties.
The major classifications of glass used in wine glasses that are commonly known include the following:
- Glass (soda-lime glass, etc.)
- Crystal glass
These classifications are fundamentally based on the types of various raw materials and their mixing ratios when manufacturing glass. Crystal glass, in particular, “previously” referred to glass mixed with lead, specifically lead oxide (PbO).
In other words, the major classification of glass types used in wine glasses was conducted based on whether lead was included in the composition.
“Crystal Glass Contains Lead” is Already a Matter of the Past
Crystal glass originated from the technique of mixing lead oxide into glass raw materials as a method to increase the refractive index and improve transparency. The glass thus manufactured possessed such high transparency, resembling crystal, that it was named “crystal glass.”
Incidentally, in terms of material definition, crystal is a crystalline substance, whereas glass is a non-crystalline (amorphous) substance. Therefore, this nomenclature represents a coined term combining completely contradictory words.
When lead oxide is mixed into glass, not only does the refractive index increase, but the melting temperature decreases, improving processability. Additionally, characteristics can be obtained such as increased specific gravity in proportion to the mixing ratio, and hardened resonance with extended reverberation. Due to these properties, crystal glass was preferentially used in high-quality wine glasses.
However, the current situation has changed dramatically.
Lead-Free Crystal Glass with Lead Removed is Currently Mainstream
From the past, claims have been propagated that lead dissolves from the surface when liquids are placed in crystal glass, leading to health hazards. In reality, lead dissolution from the glass surface does not occur in quantities that would be harmful to human health. However, it is factual that a considerable number of people held such perceptions.
In addition to this, the RoHS Directive (Restriction of Hazardous Substances Directive), regulations aimed primarily at reducing environmental impact in electronic and electrical industrial products, was adopted by the EU (European Union). The significant influence came from lead being incorporated as a regulated substance in this directive.
In practice, regulations under the RoHS Directive do not have enforcement power over the manufacturing of glass products for food use. However, against the background of such social trends, the movement toward lead-free wine glasses accelerated.
Currently, virtually all major companies renowned for wine glass manufacturing, including Riedel, Schott, and Zwiesel Kristallglas, are manufacturing their crystal glass products using lead-free crystal glass formulations that do not employ lead oxide.
Additionally, some products employ techniques that enhance glass surface durability by forming extremely thin films on the glass surface.
Elements That Change When Glass Material Changes
When the material used in glass manufacturing changes—that is, when the raw material formulation changes—the following aspects change:
- Glass surface condition
- Weight (specific gravity)
- Sensation when held in the hand
- Sensation when placed to the lips
- Transparency
- Resonance
Each of these aspects exerts a non-negligible influence on the taste perception of wine as experienced by humans.
Glass Surface Condition Influences From Both Physical and Chemical Perspectives
Differences in glass surface condition due to raw material formulation variations influence wine taste perception from both physical and chemical perspectives.
In fact, it has been demonstrated that the surface condition of glass formulated with lead oxide forms extremely fine irregularities, whereas the surface of soda-lime glass and similar materials is flat. Consequently, the surface area of the glass is broader compared to ordinary glass.
These fine irregularities contributed to enhancing wine volatility when swirling wine within the glass, thereby making aromas more pronounced.
Furthermore, changes in formulation can be expected to alter the chemical electric charge state of the glass surface. This change also becomes a factor that can potentially bring about changes in the state of ionic bonding with components in the wine, thereby influencing the perception of wine taste and aroma.
Beyond perceptual changes based on such differences in glass surface condition, factors such as the sense of weight when holding the glass, the texture of the glass, and the sensation when placing it to the lips also influence the impression of the wine poured into that glass.
It should be readily understandable that when wine is poured into a glass whose texture is soft to the touch and which imparts a smooth impression when placed to the lips, impressions held toward the glass—such as “soft” or “smooth”—are easily attributed directly to the wine within that glass.
This tendency is considered to intensify particularly when the rim of the wine glass is thin, making it easier to perceive the glass and wine as a unified entity.
Material Differences That Are Difficult to Compare
While influences of glass shape on taste and aroma perception can be readily compared, conducting comparisons of influences brought about by differences in glass material used is extremely difficult.
This is because in order to measure differences limited to material variations, all other elements must be identical. This means that not only must the shape of the glasses used in comparison be completely identical, but the weight per glass must also be identical. Furthermore, coatings applied to the glass surface fundamentally need to be entirely removed.
Certainly, glass weight is based on the specific gravity of the material. However, the influence on perception derived from this is due to “weight” rather than “material.” If both the glass surface condition differs and the weight differs, it becomes impossible to determine whether the perceived difference originates from surface condition or weight.
Therefore, in order to measure differences in perception due to variations in glass material, it inevitably becomes necessary to prepare glasses that are identical in shape and weight but differ only in the material used.
However, glass weight is proportional to the specific gravity and size of the material used. If a material with high specific gravity is used, a glass of identical size will increase in weight. Conversely, if one attempts to adjust the weight of either glass by increasing or decreasing it to make them identical, the size or shape will then differ.
Fundamentally, comparison under matched conditions cannot be conducted by any method for this comparison of “material.”
(The author abandoned treating “The Influence of Lead Content Presence or Absence in Wine Glasses on Wine Sensory Evaluation” as a graduation thesis topic during studies at Hochschule Geisenheim University for this reason.)
Certainly, some influence should be exerted on the taste and aroma perceived by humans. Nevertheless, what cannot be known is the precise range of that influence—this is the reality of differences in glass material used.
Conclusion: The Basis for Differences in Taste and Aroma Perception Due to Glass Variations Remains in Darkness
Changing the wine glass used significantly alters the taste and aroma perceived from the wine poured therein. This change may be brought about by changes in glass shape, differences in the material used in the glass, or by a combination of both differences.
On the other hand, the relationship between wine and the glass into which it is poured is extremely complex. Separating and evaluating each factor individually is virtually impossible.
Therefore, the discussion of what shape glass is optimal for what type of wine is, in fact, extremely nonsensical. Even if glasses appear to have identical shapes, the actual construction as glassware is completely different. In other words, even for glasses that appear to have completely identical shapes, if the manufacturer or the era in which the glass was manufactured differs, the composition differs, and consequently the taste and aroma perceived also change.
If one were hypothetically to discuss glass compatibility for a specific wine, it would be necessary to address the question to the extent of what formulation-based manufacturing, what shape, and what weight of glass would be appropriate to use.
And even with such detailed specification, the types of aroma and taste that the glass emphasizes and conveys are not necessarily preferable to everyone.
Ultimately, what exists there is not the expression of wine’s character, but merely the expression of the individual drinker’s preferences. This is precisely why Riedel conducts the Riedel Workshop—a process of making those “individual preferences” more populist and majority-oriented.
While this becomes an extremely unscientific discussion, the conclusion ultimately becomes that one should use whatever glass one favors to enjoy both red and white wines. This is the same conclusion as what the MW mentioned at the beginning practiced in daily life. This is the reality of what wine glass and wine compatibility truly represents.
