Ketchup
Even after opening the bottle, Ketchup is made of enough food additives since it contains vinegar, but the tomatoes are naturally acidic and this helps to preserve the product under ambient conditions, maintaining its quality and freshness, so you don’t have to refrigerate the condiment at all.
Melons
There’s no need to keep melons in the fridge! If you leave them at room temperature, they will maintain their natural antioxidant levels. Well, “level,” as if it were the same. That said, if melons are sliced up, they should be stored in the refrigerator and covered with plastic wrap or foil.