|MadSci Network: Biochemistry|
I found two web sites that answer your question. The first (reference 1) was written by Robert Krampf, who runs a science education company in Florida, and is maintained by About. com and the second (reference 2) is from a Cyber Science journal called The Helix, which is from Csiro Publishing. Both of these claim that the disgusting tatse of orange juice that you sense just after brushing your teeth (and I presume your tongue)with toothpaste is the result of detergents (e.g., sodium lauryl sulfate), which are present in toothpaste, blocking the functioning of your sweet taste buds without inhibiting (reference 1), and possibly even enhancing (reference 2), the functioning of your sour and bitter taste buds. Oranges contain acids (malic acid and ascorbic acid- see reference 3 from a Mad Sci site). The pH of orange juice is 4.2 according to information found in the MadSci site in reference 4. Acids taste sour. In fact, the word acid comes from the Latin word acidus, which means sour (see MadSci site in refernce 5). Normally, the sour (acidic) taste is covered (at least partially) by the sweet taste produced by the sugars that are present in the orange. However, if your ability to taste the sweetness is blocked, then the acidic taste will predominate. A similar, but less mechanistic, conclusion is found in a 1997 Mad Sci answer to this question (reference 6), which states that "brushing your teeth may stimulate the taste buds on your tongue...". REFERENCES: 1 http://kidshealth.about.com/kids/kidshealth/library/weekly/aa051900a.htm 2 http://www.publish.csiro.au/cyberscience/helix/TH49/TH49B1.htm 3 http://www.madsci.org/posts/archives/jun99/927818980.Sh.r.html 4 http://www.madsci.org/posts/archives/mar2000/953662129.Ch.r.html 5 http://www.madsci.org/posts/archives/oct2000/971708740.Ch.r.html 6 http://www.madsci.org/posts/archives/aug97/870196053.Ch.r.html
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