Question: What Causes An Apple To Turn Brown From The Core Out?
By: Senacagirl
Published: March 28, 2010

Skin is blemish free.  First bite in is fine.  The closer to the core you get, the flesh of the apple is getting browner and browner???????

Answers:
Curt

Apples...like a lot of other fruit...ripen from the inside.  The core is the brain of the fruit.  Everything the apple brings in comes through the stem into the core and then out into the meat of the fruit.  You never know until you bite into it.
The Taste Of Ca...

I don't what causes it but I know how to avoid it.  Just add a little bit of lemon to the cut apples and they won't go brown.  Also works with bananas.  The acid stops teh fruit oxidasing and it won't go brown.
Janusz Walentynowicz

"Brown Core" is a low temperature storage disease
See : http://postharvest.tfrec.wsu.edu/marketdiseases/browncore.html