The end of the laws of Sheichar Akum (non-Jewish beverages) brought in Siman 114, deals with various solid food items where it was the common-practice of non-Jewish merchants to sprinkle wine on them to give them a pleasant scent. Although this isn't really practiced so much today, there is an interesting side halacha that we also learn here that has many practical applications today.
In 114:8, the Shulchan Aruch says: "...to buy pickled olives from them is permissible, even if the olives are so soft that their pips are slipping out and we are not concerned that they put wine in it, but you have to make sure that the olives were not cut with their knife." The Rema explains: "Because since the olives are sharp, they will absorb the non-kosher taste from the knife that was used."
This halacha is very much applicable to us today. Let's say you're in the fruit market and spot some very tasty-looking pre-cut watermelon. Can you buy it? You didn't see what knife was used? Based on the Rema it seems that the only situation where you can't buy a pre-cut food item is when it is charif (sharp). But with things that are not charif, perhaps it should be permissible?
Another basis for this position is found in YD Siman 96, where the Shulchan Aruch deals with the kashrus of a knife in the context of hilchos basar b'chalav. There he says that lemon juice and salted fish prepared using a non-kosher knife are permissible. The Rema says that since the non-Jewish food preparer uses the same knife to cut so many of them, the non-kosher taste that might have been in the knife initially got absorbed in the first few lemons and then went away. The Shulchan Aruch then says that if they cut cucumbers with their non-kosher knife or if it was cut with a kosher fleishig knife and you want to eat the cucumber in a dairy meal, then it is permissible as long as you scrape off the edge of the cucumber. In halacha this is called "b'greide bilvad." But this is only if it was an individual cucumber, but if they were cutting many, then the same leniency as with the lemons would apply.
So what does one do in the watermelon case? Horav Shmuel Felder, shlit"a says that based on what we've just said above it should be permissible. He mentions that some rabbonim are still careful not to eat such fruit because they don't know what the status of the knife was. Perhaps the person didn't clean it from its other use? Perhaps he used it to cut his sandwich beforehand?
Another situation encountered on a regular basis: You go to a non-Jewish establishment (e.g. a hotel, kiosk, etc.) and order a diet coke. They bring it to you with a slice of lemon attached to the glass. Lemon is a sharp food. You don't know the status of the knife they used. In fact, it is quite likely that the knife is general purpose and is therefore used to cut a variety of things in the kitchen not just fruit. In addition, they are not cutting hundreds of lemons, just the one lemon that they served you. So this could be a real kashrus problem. The best advice is to take the lemon out and consume the drink without it. The lemon juice that already got into your drink is not an issue, because the quantity is so minute compared to the drink itself that it is batel (nullified).
Next week we will start a new siman that will deal with the issue of doing business with non-kosher food or animals. Over this period, we will examine questions such as the permissibility to sell non-kosher food, to own a pet store, or to run a zoo.