A creamy, persistent foam is soft, the crown of a great beer. Improve the appearance and facilitates the perception of aromas and flavors. We were all dazzled by the creamy appearance of Guinness Stout, where in some bars draw a shamrock on it, or the traces left on Cup by Belgian Chimay. The foam created to serve a beer acts as a network for many of the volatile compounds found in beer. These evaporate from beer to create the aroma, such as hop oils or compounds produced during fermentation as alcohol, fusels and fruity esters, spices or other additions.
What is it?
inside the bottle are liquid and gas under pressure. This pressure causes the gas to be incorporated into the liquid and create a balance. When you uncover a bottle generates an imbalance between the amount of CO2 dissolved in beer and the amount of CO2 in the atmosphere. To restore balance CO2 bubbles leave the beer to come out of the vessel causing, in the dense liquid is beer foam. Why the other drinks do not have foam?
soda, wine "sparkling", etc. Have CO2 pressure, dissolved gas, however, only do not see bubbles and foam. At most a mild mousse lasting a few seconds. Beer, unlike them, is a drink, biochemically speaking, complex, with components that facilitate foaming and others who are fighting.
Foam is a dispersion (mixture of two substances, in this case a soda and the other solid) in which the carbon dioxide dissolved in beer is enriched and mixed with substances which promote the formation of the foam. Compounds in beer is hydrophilic (that is conducive to water) and hydrophobic (the rejected), also has glycoprotein compounds that are partly hydrophilic and partly hydrophobic. When these compounds are coupled to the top of the beer a package of CO2, which forms the bubble. One of the elements that help keep the foam is the viscosity of the beer as being a heavier liquid flows slowly around bubbles, favoring the presence of the same.
In this picture we see a case High carbonation, such as industrial accustomed to take, and low viscosity of the liquid. Is a typical cause strong beer foam to serve, creating large bubbles and the foam lasts a short time, it has a creamy texture but rather seems to soap.
The final test of a healthy beer quality is the way it leaves traces or traces in a glass (foam cling). The way in which the foam adheres to the side of the glass after each drink, delicate and consistently drawing like a "fit." The real connoisseurs call "Brussels Lace." as Guinness Beer are served with a mixture of carbon dioxide and nitrogen (N2), achieving a very fine and durable foam. Nitrogen, creates very fine bubbles, which are structurally stable and take longer to explode and not being completely soluble in liquid N2 tends to leave the beer and go directly to the foam. Here must take into account the idea of \u200b\u200bbalance, the atmosphere is 75 percent N2 and 0.2 percent of CO2 and N2 do not tend to escape quickly into the atmosphere.
served in many places with too much foam, so that the liquid in the beer in the glass was smaller. The producers of the drink and the group CAMRA (the Campaign for Real Ale) is stranded in a debate to determine how much is indeed, a pint. By law has established that at least 95% off other liquid and foam. craft beer bottle that you can enjoy a special peculiarity is hardly find in a gondola, you gasification or natural carbonation. This means that at the time of bottling fermentable sugars were added (priming) and, once closed, there is a fermentation in the bottle, which generates CO2.
The dissolved CO2 is produced by the same yeast that carried out the fermentation. This means that no pressure was introduced artificially. The characteristic of this type of carbonation is that it generates smaller bubbles, which result in a more creamy, persistent foam. The ideal foam is composed of small bubbles of the same size. What gives a creamy foam. .
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