The Prohibition of Eating Food Cooked by a Gentile
There is a rabbinical prohibition to eat food that is cooked by a gentile.
This prohibition applies to all forms of cooking. It does not apply to food
which is salted or pickled.
Microwave cooking was, of course, unknown in the time of the Rabbis.
Modern Poskim have determined that the prohibition of bishul akum also
applies to food cooked in a microwave.
If a gentile pours hot liquid from the pot in which the liquid was heated
(irui kli rishon) onto food, the food is not prohibited. Irui kli rishon
cooks only the uppermost layer (the “shell”) of the food. Since this
shell alone would not be served to an honored guest, the food is not
Hot liquid that has been poured from the vessel in which it was heated
into a second vessel (kli shayni) does not cook the food placed into the
second vessel even though the liquid is still hot. Therefore, if a gentile
places food into a second vessel, the food is permitted even if the liquid
in the vessel is boiling hot.
The prohibition of bishul akum applies only when the gentile heats food
with the intention of cooking it.
The prohibition of bishul akum does not apply to foods that are normally
eaten raw. But if a gentile intends to cook a food that is ordinarily eaten
raw and he does not realize that it is combined with food that is eaten
cooked, the prohibition of bishul akum applies.
The prohibition of bishul akum does not apply in doubtful cases, for
example where it is unclear whether or not a gentile has cooked the food.
Such food is therefore permitted.
If a Jew lights the fire under a pot and a gentile then places food into
it to be cooked, Rabbi Yosef Karo (the Mechaber) forbids the food, while
Rabbi Moshe Isserlis (the Rama) permits it. If a Jew places food into a pot
and afterwards a gentile lights the fire, these authorities agree that the
food is prohibited.
Owners of restaurants and hotels which have a clientele of Jews who
conduct themselves according to Rabbi Yosef Karo (the Mechaber) should make
certain that the food cooked in their kitchens is permitted also to them,
i.e. they should conduct the kitchen according to the more stringent opinion
of the Mechaber.