2,305. Non-Kosher Brine

Maachalos Assuros 3:21

Similar to the previous halacha, we may not buy cheese and pieces of fish that don’t have signs of being kosher except from a Jew who's already known to be upstanding. When Israel was formerly inhabited mostly by Jews, one could buy these things from any Jew there. One may buy milk from any Jew in any location.

Maachalos Assuros 3:22

If a person pickles non-kosher fish, the brine is prohibited. On the other hand, brine from non-kosher locusts is permitted because they don’t have any moisture. Therefore, we don’t buy brine from non-Jews unless there’s a kosher fish floating in it; one fish is sufficient for this purpose.