Differences between synthetic stoppers and wine corks

For several generations, the cork stopper has been the traditional way to seal wine bottles, but in recent decades an alternative has emerged: synthetic cork.

What are the differences between one material and the other? What advantages and disadvantages does each have? We analyze in detail these two types of stoppers, to understand the advantages that the latest innovations in synthetic wine stoppers bring and why they are outperforming cork, especially in young wines.

Types of Cork Stoppers

Cork is a 100% natural material extracted from the bark of the cork oak tree. Therefore, its price and availability largely depend on the abundance of this tree or its scarcity due to fires, pests, or the slow development of new specimens.

Due to the variability of cork prices, there are different types of stoppers that combine other materials to reduce their cost or to solve problems related to their natural properties.

These are the most common types:

  • Natural Cork Stopper: By natural, we mean the traditional stopper, made from a single piece of pure cork. It has a porous structure that favors controlled oxygen exchange, important for wine evolution and maturation. However, its porosity can also cause contaminations and alterations in wine quality, which we will discuss later.
  • Agglomerated Cork Stopper: Made from natural cork granules agglomerated with binders. It is cheaper as it is a by-product of cork and is also less porous than natural cork. This type of cork is the most used, not only in wine bottle stoppers, but also in the construction industry and other sectors.
  • Technical Cork Stopper: It has an agglomerated inner body and one (1+1) or two discs of natural cork on the top and bottom (2+2). It offers a balance between airtightness and porosity by combining these two types of cork.
  • Micro-Agglomerated Cork Stopper: This type is also quite common, especially for young and sparkling wines. It contains cork micro-granules mixed with binders and is composed of cork at approximately 65%.

Types of Synthetic Stoppers

Synthetic stoppers were born to address some issues related to cork, such as a higher unit price or wine contamination by TCA.

Most cork effect synthetic stoppers are made with polymers or elastomers, but there are also stoppers made with polymers derived from plants such as corn or sugarcane, using biopolyethylene. These are known as bioplastic or compostable stoppers because they are more sustainable and biodegradable in nature.

Now let’s see some common types of synthetic stoppers used to seal wine bottles:

  • Plastic Screw Cap: This is a simple type of stopper, screwed onto the outside of the bottle neck. It perfectly isolates the wine, but is more suitable for economical and young wines, for quick consumption.
  • Pressure Stopper: Pressed into the neck, similar to cork. It can be made from different types of polymers and is characterized by its rigidity and good airtightness.
  • Injection Molded Polyethylene or Polypropylene Stoppers: Two of the most common synthetic materials because they are optimal for creating stoppers through injection molding. They seal tightly and are resistant.

Key Differences between Cork and Synthetics

What are the main differences between cork stoppers and synthetics? The best way to know them is to understand how the main properties differ that define the quality of a wine stopper.

Materials

Cork is a natural material, depending on its source, while synthetic is artificial, usually plastic, a much more abundant material. Being of different natures, they also have different properties.

Porosity

The porosity of the stopper is important when making reserve wines. The passage of small amounts of oxygen favors maturation and adds complexity to the wine, however, it can also be detrimental as excessive porosity can spoil it due to oxidation or entry of microbes inside.

Cork is a porous material that allows some oxygen exchange, while synthetic stoppers are impermeable and airtight.

Elasticity

Both cork and synthetic materials are elastic enough to adapt to the bottle neck. Cork is slightly more elastic and not all synthetics achieve good elasticity, except for higher-quality ones.

Flavors and Odors

Cork can impart flavors inside, which can be an advantage or a disadvantage. In contrast, synthetics are chemically inert and do not directly interact with the wine’s flavor.

Homogeneity

This characteristic refers to the uniformity between one stopper and another. Here, synthetic stoppers clearly win by being much more homogeneous, as each cork stopper is different and there may be some defective ones that spoil the bottle’s contents.

Sustainability

Cork is renewable and biodegradable. Regarding synthetics, it depends on the type of material. If made with biopolyethylene or bioplastic, they are biodegradable. However, all synthetics are recyclable.

Price

Synthetics usually have a lower price than cork stoppers. They can cost up to ten times less than natural material.

Will Synthetic Stoppers Replace Cork?

Certainly not. The fact that there are now stoppers made from high-quality non-natural materials that meet all food safety standards does not mean they can completely replace natural cork in all its uses. Synthetic stoppers for wine bottles did not emerge as direct competition to cork, but as an alternative for some types of wine and to address some drawbacks of natural cork.

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