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发帖数: 6973 | 1 C Claiborne Ray, The Borwn Apple. New York Times, Nov. 23, 2010.
http://www.nytimes.com/2010/11/23/science/23qna.html?_r=1&scp=1&sq=apple%20brown&st=cse
(An enzyme polyphenoloxidase, or PPO, oxidizes phenolic (nutritional)
compounds in the fruit into slightly colored compounds
My comment: NYT provides no explanation as to why citrict acid works, which
unlike Vitamin C, is not an antioxidant.
(a) David A Katz, Apple Browning: A Study of Oxidation of Foods. 2005.
http://www.chymist.com/Apple%20browning.pdf
See the section "Explanation."
(i) Amy Brown, Understanding Food: Priciples & Preparation. 3rd ed. Thomson
Leaming, 2008.
http://books.google.com/books?id=edPzm5KSMmYC&pg=PA275&lpg=PA275&dq=polyphenol+oxidase+%22vitamin+c%22&source=bl&ots=2c-n3TkjoU&sig=bDTjASMDZ6Sc3iKU5zEwVAG6z2Q&hl=en&ei=cS_sTPmNAoT0tgOh3NmmDw&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCQQ6AEwAzgK#v=onep
(same; see the section headlined "Phenolic Compounds and Enzymatic Browning"
in the lower right corner of p. 275)
(b) The following is more thorough.
Mark Gold, Keep Apple Slices From Turning Brown Naturally. Ezine, July 16,
2009.
http://ezinearticles.com/?Keep-Apple-Slices-From-Turning-Brown-Naturally&id=2614321
(polyphenol oxidase (PPO), also known as "tyrosinase")
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