Re: How does packaging affect decomposition of ascorbic acid in orange juice?

The decomposition of ascorbic acid is primarily an oxidation reaction.  
Orange juice packaging (as with all food packaging) is designed to minimize 
the exposure of the food to external conditions that speed up the oxidation 
process: like air, heat or light (I think light accelerates the reaction by 
exciting the molecules and making them more likely to react).  Juice 
cartons are made up of several alternating layers of different materials 
(foils, plastics and paper boards) that insulate the juice from heat, do 
not change the flavor or color of the juice, and prevent breathing and 
light penetration while it is being distributed to you.  So, in a sentence, 
packaging indirectly affects the decomposition of a number of components in 
foods and beverages by providing a barrier against undesirable reactions.

I hope I've answered your question sufficiently.  If not, pease let me know 
and I'll try to go into more detail.

Kieran