Food
When traveling from the United States on an international flight, most solid foods are permitted through security as long as they are sealed or wrapped in plastic.
Fruits and Vegetables
Fruits and vegetables are allowed, but they cannot be bitten, peeled or chopped. If they are, they must be sealed in plastic.
Liquids
No liquids more than 3 oz. are allowed, and those must be sealed in a clear, zip-top plastic bag. The liquid rule is reserved for toiletries. Don't try to bring a bottle of water or soda; you will have to throw it away at security.
Security
All food must be scanned and cannot cause any kind of mess or spill, so if there is any chance of that, the food will have to be disposed of at security.
Purchases
Any food purchased after going through security will be allowed on the flight. It might be more expensive, but at least you know it's cleared.
Medicine
The Transportation Security Administration says baby formula, breast milk and/or medicines are fine, but they must be checked by security.