Beer question??!
Answers: I have always wondered... where do the bubbles come from that appear from nowhere in your pint of beer?? There is no air at the bottom of the glass, so where do the rising bubbles coming from?
Chemistry professor explains the 'fizzics' of beer
People have watched bubbles rising in a glass of beer and wondered where it all began, but few have taken the question as literally as chemist Richard Zare, the Marguerite Blake Wilbur Professor in Natural Science. Zare published a seminal paper on the "fizzics" of beer 10 years ago, but spoke on this evergreen topic Oct. 18 at a meeting of the Santa Clara Valley Section of the American Chemical Society.
Zare's obsession with beer science began, he says, when a friend pointed out that beer bubbles got larger and rose faster as they floated to the top of a glass. The reason seemed obvious at first: As bubbles rose, pressure from the surrounding beer decreased, allowing carbon dioxide in the bubbles to expand and bubble buoyancy to increase.
But then Zare noticed that beer bubbles at the top of a glass were as much as twice the size of bubbles at the bottom. To generate that much of an increase, he realized, the pressure at the bottom of the glass would have to be eight times the pressure at the top. Some back-of-the-envelope calculations showed that a glass of beer would have to be 240 feet tall to generate that much pressure.
"That squashed my idea that I had a simple explanation," he says.
Another problem with the pressure theory: It couldn't explain why bubbles in beer should act any differently from bubbles in water. "If you took an air bubble and released it in water, it would rise at a constant velocity," says Zare. "That's not what's happening here."
It turned out that pressure differences make only a minor contribution to bubble expansion. Instead, like snowballs rolling down a hill, bubbles expand because they accumulate material as they go.
The process starts when you open a bottle of beer. The sudden drop in pressure encourages dissolved carbon dioxide to escape from the beer. Most escapes in bubbles that form at the sides and bottom of a glass, where microscopic cracks serve as starting points, or nucleation sites, for carbon dioxide to gather. When the carbon dioxide at a nucleation site reaches critical volume, a bubble detaches from the glass and launches itself toward the beer's head.
The reason that bubbles expand and accelerate as they rise is that bubbles themselves act as nucleation sites. Each attracts more escaping carbon dioxide -- or, as Zare puts it, "bubbles nucleate bubbles."
Nucleation also is responsible for the fizz that results from adding ice, sugar or salt -- all crystalline in microstructure -- to a carbonated beverage. Like cracks in glass, edges on crystals provide nucleation sites where molecules of carbon dioxide can gather.
Why does beer contain carbon dioxide in the first place? To understand that, you have look at how beer is made, says Zare. Brewers start with four ingredients: yeast, hops, malted grain and water. Turning those ingredients into a carbonated, alcoholic beverage is a three-step process. First, the brewer pours hot water over the malted grain to produce a sugar- and protein-laden soup called wort. He or she then adds hops for flavor and boils the mixture for several hours. Finally, after the wort has been cooled to room temperature, yeast is added to spur fermentation, which can take several weeks.
As yeast grow, they feed on complex sugars and other nutrients and quickly use up the oxygen dissolved in the wort, explains Zare. That forces them to switch to Plan B -- a method of metabolizing sugar that works without oxygen. Luckily for beer lovers, Plan B has two major byproducts: carbon dioxide and ethyl alcohol. In a sealed container, the carbon dioxide dissolves into the beer and sets the stage for nucleation.
Zare also addressed the mystery of why most beer bottles are made of green or brown glass, which is more expensive than clear glass. The answer has to do with a process called "skunking," in which sunlight causes chemical changes that can render a bottle of beer undrinkable.
Skunking occurs when rays of ultraviolet light strike hop-derived molecules called isohumulones, which give beer its distinctive bitter taste. By breaking a bond that bridges two parts of the isohumulone molecule, light creates two new compounds. The smaller one binds to sulfur atoms from nearby proteins to create what Zare calls "essence of skunk" -- not exactly the same foul-smelling chemical that gives skunks their swagger, but close. The compound is so potent that even amounts in the parts-per-trillion range can ruin a beer.
I think this should answer your question!
mmmmmmmmmmmmmmmmmmmmm beer that makes me want a beer now. i have no idea where the bubbles come from though.
hops have chemicals in them that develop a type of fizzing that creates the bubbles in your bottle or can or anything u put beer in
If the beer is cask or bottle conditioned, the beer is still undergoing a secondary fermentation, and is thus releasing carbon dioxide, which escapes as bubbles.
Most canned beers and mass produced draught beers in pubs are sterile, with the fermentation ended, and instead have carbon dioxide dissolved in the beer. Without it the beer would be flat.
The bubbles are carbon dioxide from the fermentation process. When the beer is kegged or bottled the bubbles are trapped in the liquid, but when poured the bubbles are released.
The bubbles are carbon dioxide, a waste gas produced from the brewers yeast as it consumes sugars in the fermentation process (yeast farts). It stays dissolved in the beer under pressure, say in a bottle or keg. Once it is poured the carbon dioxide is released as bubbles or "head". Also if you shake it up or break the surface tension on your glass it will foam again due to pressure change.
Never had a pint in the glass long enough to notice any bubbles.
But now you've mentioned it, I'm sat here watching the bubbles in my pint float to to the top. It only happens when I take a sip. Maybe that has something to do with it.
Good question.
The bubbles are from carbination,its the yeast reaction in the beer! Its like when you cut open some rustic bread and see the wholes...same concept!
Oh my God read a book.... I know it sounds like magic but they come from inside the beer. How do they get there you ask?? Its science.
yeast
bubbles are formed on tiny spots in the glass
i was once told as a landlord(by an engineer) that my cider was flat because my glasses where to clean ????
Short version:
The gas (CO2) is kept dissolved dissolved in the beer by pressure. When the pressure is released (when the beer is poured), the gas comes out of the liquid and forms on any little particles, forming bubbles. Beer is brewed without being under pressure, so the CO2 produced by the yeast escapes to the air. It's kegged with compressed CO2.
carbon dioxide. the yeast create carbon dioxide and alcohol in the fermentation process. in bottle conditioning they had corn sugar that creates lots of carbon dioxide when fermented in the bottle this is done by some home brewers. usually now beer is carbonized under pressure when bottled/keged with a tank of carbon dioxide. so u can control the consistency of the alcohol and taste much more efficiently. u also dont have to worry about bottle sediment
The glass you get your beer in are called head keepers they have a circle of cut glass at the bottom, this keeps the beer lively, have a look next time you have a pint