Dear Sommelier - UK Edition (Part 2)

Good morning! Following last week, today is our UK feature 🇬🇧

Last week, I wrote about how sparkling wine production is thriving in the UK. (Ohayou Biwako vol.125) For someone like me who had assumed that "sparkling wine thrives in warm regions," this was another new discovery. Ah, how fascinating.

If that's not the case, I thought perhaps grapes suitable for sparkling wine grow there instead, so I decided to explore further.

To begin with, what is sparkling wine?

Is it just wine with bubbles in it? Half-true and half-no.

Sparkling wine is a general term for effervescent wine that has carbon dioxide trapped inside the bottle.

Furthermore, wine with a gas pressure of 3 atmospheres or more is defined as sparkling wine.

"Champagne," famous as a wine with bubbles, is also included in the sparkling wine category. (Its gas pressure reaches 5–6 atmospheres.)

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・Less than 1 atmosphere: Called semi-sparkling (or lightly sparkling) wine, and isnot classified as sparkling wine.

・1–2.5 atmospheres: Called semi-sparkling wine and isclassified as sparkling wine.

These are called "Pétillant" in French and "Frizzante" in Italian. (In French, "Pétillant" means "popping" or "sparkling," and the Italian "Frizzante" comes from "frizzare" (to pop, to tingle). Popping wine, sparkling wine, tingling wine. Hmm, for some reason, these foreign words sound more stylish.)

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I wondered about the 2.5–3 atmosphere range, but it seems to be a case-by-case basis depending on the carbonation—sometimes included as semi-sparkling, other times treated as sparkling.

By the way, beer is about 1.5–2.6 atmospheres, and carbonated water is about 3 atmospheres. I’ve convinced myself that it’s why drinking carbonated water makes me feel like I’m having an alcoholic beverage.

■ What does pressure mean in beverages?

It represents the amount of pressure exerted by the carbon dioxide gas dissolved within the bottle.

1 atmosphere is the pressure based on the weight of air felt at sea level on Earth. For example, the air we normally breathe is at 1 atmosphere.

In the case of wine, carbon dioxide is dissolved into the liquid inside the bottle, and the "pressure" is measured by the force the gas exerts against the inside of the bottle. The higher the pressure, the more carbon dioxide is dissolved, which is why it bubbles more vigorously when opened.

Now, is it more common to inject the carbon dioxide, or to use the traditional method of secondary fermentation in the bottle?

How is sparkling wine created?

As for which is the most common, the answer is a different method entirely.

It is called the "Charmat method," named after Frenchman Eugène Charmat, who invented this process. In Japanese, it’s called the sealed tank method, where secondary fermentation takes place in a closed tank.

1. The Charmat Method

First, still wine that has finished its alcoholic fermentation is created and placed into a tank. By adding sugar and yeast, alcohol and carbon dioxide are produced, and the gas dissolves into the wine, creating bubbles.

There are many types of sugar and yeast—what kind is used?

Looking into it, it seems a mixture called "liqueur de tirage" (a mix of sugar and yeast) is used. In French, "Tirage" means "to pull." It seems the word came from the idea of "pulling out" or "initiating" secondary fermentation.

It is made by mixing the following components:

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・Sugar: Primarily sucrose derived from sugarcane or sugar beets, or concentrated grape must.

→ Sucrose does not remain as sweetness after fermentation and doesn't spoil the wine's flavor, making it suitable for secondary fermentation. Concentrated grape must is also sometimes used as it contributes to the wine's natural flavor.

・Yeast: Primarily Saccharomyces cerevisiae.

→ Used because it has extremely high alcohol tolerance and can work actively even in high-alcohol environments. The yeast cell membrane contains lipids (a bilayer) that protect the cell from damage by alcohol. Saccharomyces cerevisiae enhances the stability of its cell membrane by containing a high amount of specific lipids (e.g., ergosterol), which counters the destructive effect of alcohol on the membrane. There is even a theory that it can survive in up to 23% alcohol.

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Since the tank is a sealed space, the wine barely touches the air, which is a key feature as it minimizes the effects of oxidation.

Wine oxidation is a phenomenon where contact with oxygen changes the aroma and taste. Phenolic compounds in the wine (such as polyphenols) react with oxygen and change into a substance called "quinone." This quinone reacts with "aromatic thiols" (e.g., grapefruit or tropical fruit aromas) that compose the wine's fresh aroma, causing them to be lost.

Also, during the oxidation process, reactive oxygen species such as "hydroperoxyl radicals" or "hydroxy radicals" are generated. Hydroxy radicals oxidize ethanol (alcohol) to produce acetaldehyde. This can cause unpleasant aromas. Organic acids such as tartaric acid and malic acid are oxidized and turn into keto acids (e.g., glyoxylic acid). This changes the taste and can result in unpleasant flavors.

The Charmat method allows for large quantities of wine to be produced in a shorter period (about 2 weeks to 2 months) compared to in-bottle secondary fermentation and with less effort, which is why it is used for manufacturing reasonably priced sparkling wines. (e.g., Italian "Prosecco" and "Spumante")

Carbon dioxide gas gradually becomes more integrated into the wine liquid when kept under high pressure for a long time, resulting in fine bubbles. The Charmat method, which has a shorter duration and lower pressure compared to in-bottle secondary fermentation, is characterized by having relatively larger bubble sizes.

Now, let's look at the features of the carbonation injection type and the in-bottle secondary fermentation type 🔍

2. Carbonation injection method

Carbon dioxide gas is injected directly into a still wine that has already been completed. Because it is "already completed," the flavor, aroma, sugar content, acidity, and alcohol content do not change. Because the gas and liquid are in contact for only a short time, the bubbles are large and have a sharp, popping sensation, and the carbonation also dissipates quickly.

It is relatively simple, can be produced in a short time, and allows for mass production, so it is often used for low-cost, casual sparkling wines. (e.g., Italian "Secco," German/Austrian "Perlwein")

3. In-bottle secondary fermentation method

This is the traditional way of making sparkling wine and is used for high-quality sparkling wines like Champagne and Cava. In this method, secondary fermentation takes place inside the bottle, naturally producing carbon dioxide and dissolving it into the wine.

The method of triggering the secondary fermentation is the same as the Charmat method—"liqueur de tirage" is added. While the Charmat method is in a tank, this is done in the bottle. After leaving it for 6–8 weeks, it enters a period of "aging."

During this "aging" period, after the yeast dies (becoming lees), a phenomenon called autolysis occurs, where the components within the cells dissolve into the wine. Lees are lumps of protein. At that time, umami components such as amino acids and peptides are released into the wine, adding "bread" and "nutty" aromas and flavors.

As these amino acids slowly react with the sugar remaining in the wine, the Maillard reaction occurs, generating compounds (e.g., pyrazines, furfural, etc.) and creating the characteristic "bread" and "nutty" aromas and flavors.

The aging period is 15 months or more for Champagne, 9 months or more for Cava, and some are even aged for more than 3 years. "Dom Pérignon," for instance, is said to be aged for over 8 years.

I've covered the manufacturing methods of sparkling wine in detail, but let's not forget that this is the UK edition 🇬🇧 In the UK, which of these three methods is used?

UK Sparkling Wine

I didn't have any clues, but I thought, doesn't the UK insist on high quality? And sure enough, in the UK, it is primarily made using the in-bottle secondary fermentation method.

There must be a good reason why it's made via in-bottle secondary fermentation. When I looked into it, it seems to be related to the characteristics of the grapes grown in the UK. Let's take a closer look.

Grapes preferred for in-bottle secondary fermentation are grapes with high acidity. During aging, the wine's fresh fruitiness gradually softens, and the aromas derived from aging (bread and nutty aromas) come to the forefront. At this time, grapes with high acidity are important as they maintain the overall balance of the wine and ensure it doesn't lose its freshness or sharpness.

Also, grapes whose aromas change easily through aging are preferred. For such grapes, what started as fresh aromas (green apple or citrus) when young change into savory aromas like bread and nuts when aged. As the aroma becomes multi-layered over time in this way, the impression and finish when drinking the wine become richer, and you can feel the depth of flavor.

The grapes that grow in the southern part of the UK, which accounts for 83% of the country's grape cultivation area, satisfy these exact conditions.

This region has a cool climate. As a result, the grapes mature slowly and photosynthesis occurs gradually, meaning malic acid isn't consumed rapidly, which tends to keep acidity high. Additionally, because aroma components (e.g., terpenes and esters) in the grapes are not broken down but rather retained, it is also a characteristic that fresh aromas like citrus and green apple remain. (Conversely, in hot climates, sugar content rises rapidly, which can emphasize heavy aromas like those of ripe fruit (tropical fruit).)

Also, this region features chalky soil (limestone soil), which is similar to the Champagne region. Because this soil drains well, the roots grow deeper and deeper in search of moisture. (If drainage is good, moisture moves to lower layers due to gravity, and the roots grow deep in pursuit of it.) As a result, mineral resources accumulated underground are absorbed by the grapes. This minerality is an element that adds complexity and depth to sparkling wine.

So, what kind of grapes are they? They are "Chardonnay," "Pinot Noir," and "Pinot Meunier."

These grapes are characterized by high acidity and the freshness derived from a cool climate. Thanks to the chalky soil, a mineral quality is added, enhancing the individuality of each variety. Compared to other regions (especially the Champagne region), many more light and fresh styles can be seen.

British sparkling wine, carefully crafted using such grapes and the in-bottle secondary fermentation method, has fine bubbles and complex flavors, and has won numerous awards at international competitions.

As global warming progresses, there is a possibility that the Champagne region may gradually become hotter, and some say the center of sparkling wine production may move north in the future. Perhaps the day will come when the UK becomes the center for the next generation of high-quality sparkling wine.

When that happens, maybe we'll see sparkling wine with names inspired by "Kent" or "Sussex," where the grapes are grown, instead of "Champagne"?