Exact food category of a food item

This is impossible for most items.

If you're creating a shop, you have to choose how to categorise things to make the most sense (or the most sales); you also have to choose the categories. If you're not creating a shop but trying to match existing shops, realise that they don't all decide the same. For example in one supermarket granulated sugar is in the aisle labelled "tea and coffee", in another it's under "home baking", and those supermarkets' websites match their physical stores. Presumably you get to decide what categories are available. That doesn't make it any easier.

The question of whether a hamburger is a sandwich is not just a good example of the difficulty of categorising food, but of the fuzziness of categories in human life.