Cut fruit looses about 10% to 25% of its vitamin C and other oxidizing nutrients after 6 days in refrigeration; it visibly spoils before nutrition loss is significant. Most oft-cited paper with this result is Quality Changes and Nutrient Retention in Fresh-Cut versus Whole Fruits during Storage (American Chemical Society), you cans find a brief summary from the NYT Nutrition desk here: http://www.nytimes.com/2006/06/06/health/nutrition/06nutr.html, and a google search for "cut fruit loses nutrition" has top results mostly pointing to that study. An argument can be made for pre-cut vegetables and fruits being less tasty after a week of near-freezing refrigeration, but this "4 hours" thing is malarky.
I found a few articles discussing vitamin C reacting with free iron & copper in a H2O2 (hydrogen peroxide) solution to become a free r