Ten Things You Didn’t Know about Keeping Kosher

Ever wonder why those Jewish neighbors of yours don’t want to eat in your house? Learning more about Judaism and wondering about keeping kosher? Here are some of the obscure things your neighbors might be concerned about. Keep in mind that not every Jew who keeps kosher observes the laws strictly, and even within Orthodoxy there are many variations.

Naturally, ask your local Orthodox rabbi for more details. . .

  1. Knives. When it comes to knives and sharp foods such as onions and garlic, the halacha (Jewish law) is strict. If you cut an onion with a clean dairy knife, you have to slice off the layer of onion that touched the knife before using the rest of the onion in a meat meal.
  2. Bugs. They ain’t kosher. Unless they’re grasshoppers and you *know* that they are the kosher kind. Depending on where you live, some vegetables and grains need to be checked before they are eaten. Flour may need to be sifted with a fine sieve. In Israel you can find bugs in anything. . .
  3. Liver. Most people know about this but I recently heard a few stories. Liver cannot be soaked and salted like other parts of beef and chicken. It must be broiled on an open flame, using utensils used just for that purpose.
  4. Terumot and Maaserot, Orlah, and Sheviit/Shemitah—-Tithing, fruit that is from a tree until the fourth year (the King James version of the Bible calls it uncircumcised fruit :-)), and the sabbatical year. These mainly apply in Israel, but you never know when you are going to get there! Could be an issue in the US if you have fruit trees.
  5. Wine. To avoid intermarriage, the sages prohibited drinking wine or any grape product that was handled by a non-Jew. Also, wine was important in many idolatrous cults. Since cooking wine lowers its quality, “yayin mevushal” or wine heated to a particular temperature, doesn’t have any restrictions. Neither do other types of alcoholic beverages beyond normal kashruth restrictions.
  6. Taking challah. When baking with dough or batter using a large quantity of flour, you need to separate a kezayith (olive-sized part) of dough, recite a blessing, and burn it or put it in a place where it won’t get eaten until it’s inedible. According to my son the Mishnah on challah is the only one written in the feminine gender.
  7. Selling chametz (leavened food such as bread and noodles). Chametz not used up by Passover may be sold to a non-Jew (according to some). After Passover, it could be a problem to buy chametz from stores owned by Jews.
  8. Fish and meat. The halacha forbids eating fish and meat together. So fish is always served as a separate course during a meat meal, using separate plates and utensils. You are supposed to eat or drink something neutral between the fish and the meat.
  9. Nine and ten are not about kashrut, strictly speaking: Netilat Yadayim or ritual hand-washing. In order to eat bread one must wash by pouring water over each hand with a cup, saying a blessing for washing, another one for the bread. adn then eating. Afterward there is a another longer blessing called birkat hamazon. So observant Jews don’t eat bread as a snack.
  10. The kailim mikveh. Metal and glass utensils generally need to be immersed in a mikveh or ritual bath before their first use. There’s a blessing for that too. Many rabbis hold that it’s okay to eat food that was not “toiveled” on a temporary basis.


  1. Larry Lennhoff says

    Nice post. I especially appreciate that you know how to deal with onions. My wife loves to ask people about that – it is astonishing how many FFBs answer either save the onion for later and use another one or just throw the onion away.

    Just to quibble, the seperation of fish and meat is not a kashrut issue either. If you cook fish and meat together in a pot, the food is forbidden, but all you have to do is wash the pot. Kashering is unecessary. Fish and meat combinations are forbidden by the Shulchan Aruch and the Talmud (but not the Rambam) because of ‘danger’ (sakana). In particular, the combination leaves you at risk for the mystical skin affliction tzarat.

  2. mother in israel says

    You’re right — I should have included it with the last two.

    Thanks for your comments!!

    Regarding the onion, I am planning to give a seminar on how to cook and shop frugally, including how not to waste food. I’ll have to remember that.

  3. mominisrael says

    Joe, everyone has different standards. My purpose was to help people be aware of the main issues that may be involved. Even my standards vary, depending on the circumstances. For instance, I might eat things at a relative’s house that I might not eat when visiting a friend. Generally I eat at the home of anyone who is shomer shabbat, even if I know their kashruth standards are lower than mine in some areas.

  4. Jerusalem Joe says

    Interesting but not enlightening. I still do not understand what i can and cannot serve to religious people, and when I ask them I get different answers from different people.
    Some will eat from my regular plates, some only from plastic, some from a paper cup some not, some only cold food, some it doesn’t matter.
    anyway – Hag Sameach.