The question was asked if it is permissible to buy pre-cut fruit from a supermarket that sells non-kosher foods. For example, certain supermarkets sell packaged pre-cut fruit such as watermelon and cantaloupe. Is it permissible to buy this fruit from an unkosher supermarket?
The concern in this situation is about the knife they use to cut the fruit and if it is a clean knife that has not been used to cut non-kosher meat or fish. There is a very strong presumption that can be made that the knife they use is a clean knife for the simple reason that hygienically it’s more logical to use a clean knife. Also, if they were to use a knife that had meat on it, it would give a bad taste to the fruit that they are trying to sell. Therefore it’s a fair presumption to make that the knife they are using is a special clean knife for the fruit.
In a worst case scenario, they might use a knife that has meat on it from a previous cutting of ‘taref’ (unkosher meat or fish). However, already by the second slicing of the fruit that they are packaging to sell, the knife has become clean from the fruit itself. So even if one was to assume that there is some film of not kosher meat or fish that’s on the knife, the fruit itself cleans it off. Therefore we rely on the concept of ‘Bitul’, that there is no question that the small amount of film that might be on knife becomes nullified in the majority of the fruit.
Halacha Lema’ase, it’s permissible to buy packaged pre-cut fruit from a non-kosher supermarket without being worried and concerned that the knife used may have been previously used to cut something that wasn’t kosher.