Now back in the good old sauna that is also called Singapore I had to make a half scientifical experiment and allow me to present the findings below:
Apple does indeed retain it's greenish color up until the moment I just couldn't resist anymore and had to take a bite or two. Testing the taste of the apple reveals also interesting results: apple has kind of a salty (?) outer layer which seems to preserve the juiciness.
Google to the rescue when trying to understand the chemistry behind all of this and solve the puzzle once and for all:
"When an apple is cut (or bruised), oxygen is introduced into the injured plant tissue. When oxygen is present in cells, polyphenol oxidase (PPO) enzymes in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colorless precursors to brown-colored secondary products. O-quinones then produce the well documented brown color by reacting to form compounds with amino acids or proteins, or they self-assemble to make polymers. [snip]
the level of PPO activity and concentration of substrate--here, the phenolic compounds--can vary between varieties of fruits (say, Granny Smith versus Red Delicious [or Singapore apples vs. rest of the world]). In addition, a tissue's PPO level can vary depending on growing conditions and fruit maturity. One approach the food industry employs to prevent enzymatic browning is to select fruit varieties that are less susceptible to discoloration—either due to lower PPO activity or lower substrate concentration."
(source: Scientific American (now, is that an oxymoron? :) ))
PS. It might not be too far fetched to speculate that the title of this blog post has been somewhat inspired by the way episodes of Big Bang Theory are titled.
