What Do Wine Stabilizers Actually Stabilize? | About Gum Arabic (Acacia)

"Wine is made from grapes alone." This is what most people believe, yet contrary to this assumption, some wine back labels include listings of additives.

There are several types of additives, with antioxidants and stabilizers being among the most well-known. Antioxidants primarily use sulfur dioxide (SO₂), also known as sulfites. While this substance is occasionally misunderstood as a preservative or blamed for causing headaches, it is relatively well-known as a compound. Stabilizers, on the other hand, remain largely unknown both in terms of their purpose and the substances used.

The main stabilizing agents used in wine include metatartaric acid, carboxymethylcellulose (CMC), and gum arabic. In Japan, the addition of metatartaric acid to food is not permitted, and CMC is only allowed for certain specific compounds, creating regulatory restrictions.

Among these, gum arabic faces relatively lenient regulations. This article will explore what wine stabilizers actually do, focusing on gum arabic, which is commonly encountered in Japan.

Stabilizers Don't Stabilize Wine's Flavor

Stabilizers, as their name suggests, are additives used to stabilize something unstable. But what exactly is unstable in wine?

Wine itself is inherently unstable. Once a bottle is opened and left for a while, chemical changes called oxidation immediately begin, altering the taste and aroma. Given these circumstances, many people assume that wine stabilizers serve to stabilize the wine's flavor and prevent oxidation.

However, consider this: wines already contain separately added "antioxidants" that specifically serve to suppress wine oxidation. There's no need for stabilizers to take on this role.

Importantly, wine stabilizers do not stabilize the wine's flavor.

Precipitation That Stabilizers Suppress

It's well-known that wines, particularly those aged for extended periods, develop sediment called lees at the bottom of the bottle. This sediment contains tartaric acid, phenolic compounds including tannins, proteins, and sometimes metallic compounds.

What stabilizers actually stabilize is the precipitation of these substances.

In this context, "stabilization" can be directly translated as "suppression" without any problem. Stabilizers are added to prevent insoluble substances contained in wine from precipitating and settling out.

Some components in wine precipitate through oxidation processes. Therefore, preventing such precipitation can indirectly prevent wine oxidation or maintain flavors that would otherwise precipitate out and be lost from the wine, thus stabilizing the wine's taste. However, these are secondary effects.

Different stabilizers target different precipitates. Metatartaric acid and CMC are primarily used to prevent tartaric acid precipitation. Gum arabic, however, has relatively low performance in preventing tartaric acid precipitation.

What gum arabic suppresses is the precipitation of phenolic compounds including tannins and metallic compounds. Additionally, adding gum arabic has been shown to improve foam retention in sparkling wines.

Overview of Gum Arabic

Gum arabic is produced from tree sap collected from acacia trees. It's a 100% natural product used primarily as an emulsifier, with Africa being the main production region.

Production locations and tree species are not uniform, and product characteristics vary accordingly. The primarily used varieties are sap collected from trees classified as Acacia senegal (Vulgares) and Acacia seyal (Gummiferae).

Since gum arabic trees belong to the acacia genus, wine back labels sometimes list them as "stabilizer (acacia)" or refer to them as acacia gum.

Gum arabic has extremely wide applications, used not only in foods and beverages but also in pharmaceuticals, textiles, inks, and paints. Annual global consumption reportedly reaches 60,000 tons.

Chemical Structure and Properties of Gum Arabic

Gum arabic's important properties are realized through its chemical structure.

Gum arabic consists of polysaccharides including galactose, arabinose, rhamnose, glucuronic acid, and small amounts of protein. The proportions of each component vary depending on production region, tree age, sap collection location, and harvest season. These compositional differences affect the resulting gum arabic's properties.

Gum arabic dissolves well in water, hot water, and wine. It was once used in syrups and, perhaps due to images from the term "gum syrup," is often thought to be highly viscous. In reality, it has lower viscosity compared to other high-molecular polysaccharides. However, as the added amount increases, viscosity increases proportionally.

Despite the name "gum" and associations with "polysaccharides," gum arabic itself is tasteless and odorless.

Purpose of Gum Arabic Use: Protective Colloid Properties

The primary reason gum arabic is used as a stabilizer is its emulsification properties, also called protective colloid properties. While terms like emulsification and protective colloid properties may be unclear, they essentially refer to the ability to keep insoluble substances dissolved.

The original purpose of adding stabilizers to wine is to prevent precipitation of substances contained in wine.

Why do some wine components precipitate? Because these substances inherently have insoluble characteristics in wine (including its water and alcohol content). This follows the same principle as oil not dissolving in water and separating instead.

Emulsification properties, to put it simply, refer to the ability to dissolve oil in water.

Gum arabic contains both hydrophilic polysaccharide portions and hydrophobic protein portions. Imagine it as having one hydrophilic hand and one hydrophobic hand. Hydrophilic substances tend to bond with hydrophilic substances, while hydrophobic substances bond with hydrophobic substances.

When gum arabic is added to wine, the hydrophobic hand bonds with wine-insoluble oil-like substances such as phenolic compounds. Simultaneously, the hydrophilic hand bonds with water in the wine. As a result, through gum arabic's mediation, naturally insoluble substances like phenolic compounds dissolve into wine, or at least become less likely to separate from it.

Does Gum Arabic Change Wine's Flavor?

Gum arabic itself is considered to have no taste or aroma. While verification studies specifically on wine are limited, studies on other food products consistently report no impact on sensory evaluation except for color.

However, astringency and puckering sensations in wine result from tannins binding with mucin and salivary proteins in the mouth. In wines with added gum arabic, tannins become encapsulated by the gum arabic, making such reactions less likely. In this sense, adding gum arabic may change wine's taste and impression.

The amount of gum arabic added also influences these effects. Some studies indicate that additions exceeding 70 ml/hl change impressions of wine taste. However, amounts needed for preventing precipitation of phenolic compounds and metallic compounds fall below one-third of this threshold. In other words, when used solely for its intended stabilizing purpose, the likelihood of gum arabic affecting wine taste or impression is quite low.

When added to wine, most countries and regions don't legally regulate upper limits, leaving addition amounts to winemakers' discretion. If desired, high-concentration additions that affect wine viscosity are possible. Viscosity changes alter the perceived body of wine. Additionally, some cases involve high-volume additions to soften flat, simple wines or harsh tannins, though such practices cannot be completely ruled out.

Reasons for Using and Not Using Gum Arabic

The reason for using stabilizers, including gum arabic, is time reduction and process simplification. Substances that can be stabilized with gum arabic, metatartaric acid, or CMC can also be stabilized through other means without these additives.

However, costs for alternative methods are significantly higher.

These costs involve equipment, labor, and time. The primary reason for using additives is cost reduction. Conversely, when costs can be sustained, there's no reason to use additives that require mandatory back-label disclosure.

Back-label ingredient listings carry the risk of damaging brand image to some degree.

Additives don't fundamentally change wine taste. They don't make wine better or worse, nor do they change post-opening shelf life. They simply save time.

Focusing on gum arabic, the most significant impact is on tannins and other phenolic compounds.

It can resolve phenolic instability during winemaking without time or effort investment. This means wines can be bottled immediately without aging for months or years for stabilization. For consumers, wines that should exhibit strong astringency or puckering sensations instead feel approachably mature right away.

Why Gum Arabic Is Disliked

The temporal gap likely explains why stabilizer use often becomes controversial.

The more wine knowledge one possesses, the better one can predict a bottle's taste characteristics based on variety, vintage, and production region. This includes expected impressions from phenolic compounds. Wines with added gum arabic rarely match these expectations. Moreover, since this stabilizer affects phenolic changes not only during bottle storage but also after opening and pouring into glasses, the discrepancy becomes even more pronounced.

Even if the wine becomes more approachable, it creates impressions different from its natural state, likely resulting in negative perceptions.

Incidentally, phenolic stability after opening doesn't mean wine won't oxidize. Whether or not stabilizers are added, wine will oxidize, and this process accelerates after opening.

Reasons for Not Using: Lack of Necessity

Unstable wine components can be stabilized without stabilizers. The issue lies in the associated costs of time, equipment, and other factors.

Various price points exist in the wine market, from bottles under 500 yen to those exceeding hundreds of thousands of yen. Naturally, different prices allow for different cost investments.

If costs required as alternatives to stabilizers can be recovered through bottle prices, there's no reason to use stabilizers.

These costs include the period from harvest and vinification to sales. While reasons vary by winery, many need to sell wines immediately after harvest and vinification. Such wineries physically cannot afford time costs for stabilization, making stabilizer use potentially essential as an alternative. However, such necessities can often be avoided through equipment investments, where return on investment becomes the determining factor.

Stabilizers essentially stop naturally occurring phenomena in wine artificially, somewhat forcibly maintaining the current state. Unless there are special intentions or reasons, there's neither reason nor necessity to use them. Casual use only emphasizes the unnaturalness that makes gum arabic disliked.

Cultivation capable of harvesting sufficient-quality grapes, vinification allowing necessary time investment, equipment enabling such processes, bottle prices and sales capabilities supporting these economically, and customer bases tolerant of changes in wines produced this way—wines meeting these criteria don't require stabilizers.