While some of the food can be kosher, it is presently not possible for an astronaut on ISS to maintain a completely kosher diet.
It has nothing to do with the space station per se; it has to do with our food production facility,” Kloeris told Space.com. “We have a single packaging room on the U.S. side. All of the food that’s part of our standard menu that we provide — from what I understand, in order for them to be kosher and halal, they have to be done in separate, unique facilities. Therefore, everything we package would not meet that requirement.”
Kloeris noted that it’s possible to travel with a limited allotment of kosher or halal foods, in order to honor an astronaut’s heritage; every astronaut is allowed a certain number of crew-specific containers sent to the space station, which can account for about 10 percent of their diet.
The same limitations also apply to halal food for Muslims.