Food that is edible is always considered muchan, prepared for Shabbat, and does not have the status of Muktzeh (set aside). Even if a person sells food and has food in his home that he originally thought was going to be merchandise—they bake cakes, they sell cookies, something like that—even so, if the person decides that they want to eat it and use it on Shabbat, or even move it, it is always considered muchan.
This is different from clothing. If a person sells clothing out of their house and has merchandise that they are selling, then that clothing is considered Muktzeh. Even if they changed their mind and wanted to wear something on Shabbat, they would not be allowed to do so. But with regard to food, a person always has in mind the idea that he is going to take something and eat it. Therefore, it is always considered usable and not Muktzeh on Shabbat.
Even frozen food that would be edible if it were to defrost is considered muchan, even in its frozen state, and is not considered Muktzeh. Therefore, if a person has only one loaf of bread for Seudat Shabbat (Shabbat meal) and wants to take a frozen pita or a frozen challah (braided bread) out of the freezer and use it for lechem mishneh (two loaves), it is permissible to do so, and the frozen pita is not considered Muktzeh. Even though at that moment it is not edible, it could defrost and become edible, and therefore it is not considered Muktzeh. Shabbat Shalom.