Why fresh fruits and vegetables?

My last posting "fruit juices = increased hazard of diabetes" still bothers me. The researchers did not offer any explanation, not even a hypothesis. It reminds me of numerous health and medical science articles that recommend we eat fresh fruits and vegetables but none explain why fresh. We all know freshness means better taste and smell. But scientifically, it does not logically follow that they're healthier than not as fresh fruits and vegetables, although rotten ones, obviously, should be excluded for food poisoning.

So here's my theory, or hypothesis. Many fruits and vegetables have anti-oxidants, those that scavenge free radicals in our bodies. As a chemist, I know that if something is anti-oxidant, it must easily react with oxidant, most notably in our everyday life, oxygen. Have you ever asked yourself why a cut-open apple exposed to air for a few minutes has a layer of "rust"? If you must leave it open for a while, you can put food wrap on it tightly to avoid oxygen exposure, and the rust will not appear. Like apples, many fruits and vegetables have nutrients that chemically react with oxygen, depleting the health benefit due to decreased amount of the nutrient. If they were still on the plant, the nutrient would be continuously produced. But once harvested, time is running to gradually lose the oxygen sensitive nutrient. If you must, store them in a CO2 or nitrogen environment.

Well, here I'm assuming oxygen to be the only chemical that eats aways the good stuff. But it's likely that the nutrient may degrade anaerobically. In that case, eating fresh is the only way to make best use of the healthy plants.

Back to the "fruit juices = increased hazard of diabetes" topic. Science is making progress. But there's always a little gap to reveal the secrets of real nature. There got to be something fruit juice manufacturers are missing. Before the missing part is found, let's eat fresh fruits for the time being.