What Makes Soft Drinks Lose Carbonation?

What is Carbonation?

• Carbonation is carbon dioxide gas that has been dissolved into the soft drink. Carbonation occurs naturally in some drinks such as beer and certain mineral waters, or it can be introduced into liquids artificially as is the case with soft drinks. The key to getting carbonation into the drink is to put the carbon dioxide under high pressure, which causes it to dissolve into the liquid. Low temperatures also cause more carbon dioxide to dissolve into a liquid. The high pressure must be maintained to keep the carbon dioxide from escaping the liquid. That is why cans and bottles are tightly sealed.

Opening the Soft Drink

• The hiss heard when opening a bottle or can of a soft drink is a rapid change in pressure from the inside of the can, holding the carbon dioxide in the liquid, to the lower pressures of the outside world. To test this, take a 2-liter bottle of soda and try to press on the bottle at the top where no soda is located. The plastic bottle has very little give, because the pressure inside the bottle is very high. Once opened, the same area of the bottle is easy to move, showing that the pressure is lower. Carbonation can be released from the drink once it has been exposed to lower pressure.

Slow Leak

• The major change in pressure releases carbon dioxide gas. The gas that was captured in the high pressure of the sealed container disperses quickly. The remaining gas still dissolved in the liquid develops small bubbles, which rise to the surface of the soft drink. If the drink is handled carefully and kept cool, the release of carbon dioxide from the liquid will be slow.

Speeding Up Flatness

• The speed at which carbon dioxide is released from the drink can be increased significantly. Shaking the soft drink results in more bubbles forming in the liquid, which then release carbon dioxide more quickly. The dissolved carbon dioxide is very sensitive to temperatures. The warmer the soft drink, the faster the carbon dioxide will leave the liquid. Another factor is the surface area of the container. The larger the surface area, the more room for the bubbles to escape and the soft drink will go flat more quickly.

Preventing Flatness

• The soft drink is considered flat when no more bubbles escape from the liquid. When the soft drink is flat, no carbon dioxide molecules are present. Certain steps can be taken to keep a drink from becoming flat. In bottles, removing as much air as possible from the bottle and sealing it as tightly as possible will reduce how quickly carbon dioxide escapes. It is also important to keep the drink cold so that the carbon dioxide stays dissolved in the liquid.