I'm trying to take in more Vitamin C lately, and I buy a quart of cold orange juice in the morning to start my day. It's usually sealed up - I'm guessing to keep it protected from oxygen. But once I remove the seal and start drinking from it, I have about a half bottle left of the juice, which I then carry around with me during the day -- and I don't keep it in a refrigerator.
Is the orange juice still nutritious, after being opened and sitting around for an entire day without being kept chilled?