Wicked bubbly

 作者:令狐欣     |      日期:2019-03-08 07:20:09
By Andy Coghlan THE delicious tingle as you sip a celebratory glass of champagne this Christmas will have nothing to do with bursting bubbles. By asking volunteers to dip their tongues in fizzy water, researchers in California have found that the sensation is caused by carbonic acid, a chemical irritant. Earl Carstens and his colleagues at the University of California, Davis, made their discovery with the help of acetazolamide, a drug taken to combat altitude sickness. One of the drug’s side effects is that it dulls the tingle from carbonated drinks. “It’s called the champagne blues,” Carstens says. Carstens trained his volunteers to rate the tingling sensation after they stuck their tongues into carbonated water for up to 15 seconds. The scale they used ranged from zero for no sensation, to 10 for the irritation caused by hot peppers. Later, Carstens coated half the tongue of each volunteer with acetazolamide before asking them to dip their tongues into the test drinks once more, and report the tingle on each side of the tongue. The scores were significantly lower on the side coated with the drug. Acetazolamide blocks carbonic anhydrase, an enzyme which converts carbon dioxide into carbonic acid. Carstens believes the sensation of “fizziness” depends on this reaction. “We think the carbonic anhydrase takes carbon dioxide gas, which dissolves in saliva then percolates through fatty tissue in the tongue, and converts it into carbonic acid.” Supporting evidence comes from a separate study in which volunteers drank carbonated drinks in a hyperbaric chamber, where the high pressure stopped bubbles forming in the drinks. “They still got the tingling sensation,” says Carstens. Carstens also points out that drinks containing other gases seem less fizzy. The bubbles in Guinness, for example, are composed mostly of nitrogen (for more on this see “Pure genius”,