Kashrut Basics and Not-so-Basics

Jewish dietary laws “on one foot”:

The Jewish dietary laws, known as “kashrut” or “keeping kosher”, have a number of components. This source sheet looks at the sources for the basic aspects of keeping kosher as well as some of the more complex aspects of kashrut.

Why Keep Kosher?

Reasons Why Jews Choose to Keep Kosher

1. G-d/The Torah commanded us to keep kosher.

2. Connection to family through this custom/that’s how they grew up.

3. Compassion for animals’ and hence, people’s pain, and reverence for life.

4. Self-discipline (animals eat whatever they want, however they want; people eat whatever they want but not however they want; Jews impose discipline over their urges to eat whatever they want).

5. Remembering 3 times a day that we are Jewish.

6. Separation from non-Jews and hopefully longer continuation as a distinct people.

7. Health benefits (for example, when you mix meat and milk the calcium in milk keeps the body from absorbing the iron in meat).

Context: These are some of the reasons why people choose to keep kosher in some fashion.

If your dietary choices are informed by Judaism in any way, why?

The Rules for Kosher Land Animals

Context: This is from the Biblical Book of Leviticus.

What are the rules for identifying kosher land animals?

Context: This is a video by Danny Sands, singing a song that I think he made up when he was in USY in the 1970s.

The Rules for Kosher Water Animals

Context: This is the next set of verses in Leviticus.

What are the rules for identifying kosher water animals?

The Rules for Kosher Air Animals

Context: This is the next set of verses from Leviticus. They list the “treif” (not kosher) birds.

What are the rules for identifying kosher air animals?

Context: This is from the Mishnah, Masechet (Tractate) Chullin, which is about the rules for eating meat.

What are the rules for kosher air animals?

The Rules for Kosher Creepy-Crawlies

Context: This is from the same part of Leviticus.

According to the Torah, which insects can we eat?

Context: This is again from Mishnah Chullin.

According to the Mishnah, can we eat locusts that are not from the species “chagav”?

Context: This is from the Talmud, Masechet (Tractate) Chullin, which is about the rules for eating meat. It is part of a longer discussion about grasshoppers in Chullin 65a:7-66a:8 (and see also Avodah Zara 37a:13-37b:1).

According to the Talmud, can we eat grasshoppers that aren’t from the species “Chagav”?

Context: This is from the Shulchan Aruch, a law code written by Rabbi Joseph Caro in 1563. The Shulchan Aruch has 4 sections, and this text is from the Yoreh De’ah section, which is about kashrut and other everyday matters.

According to the Shulchan Aruch, can we eat locusts that don’t come from the species “chagav”?

Context: This is from Rashi’s commentary on Leviticus 11:21, which tells the signs for kosher grasshoppers. Rashi, short for “Rabbi Shlomo ben Yitzchak”, was a French commentator on the Torah and Talmud (and a winemaker) who lived from 1040-1105.

According to Rashi, can we eat any grasshoppers today? Why or why not?

The Yemenite Tradition

According to Yemenite tradition, the edible locust referred to in the Torah is identified by the figure resembling the Hebrew letter chet (ח) on the underside of the thorax.^[2] The most common of these in Yemen was the desert locust (Schistocerca gregaria), whose color ranges from yellowish-green to grey, to reddish in colour when it reaches maturity (Hebrew: ארבה‎, romanized: arbeh, Aramaic: גובאי‎, romanized: gobai, or Arabic: الجراد‎, romanized: al-jaraad).^[3] Interestingly enough, these locusts also pose the biggest threat to crops since they swarm and can quickly fly over great distances. Indeed, some explain that the Torah permitted this species of locusts precisely because they consume all the crops.^[4] Thus, even when all the crops were eaten by the locusts, there was still something left to eat.^[5] Some explain that a distinguishing characteristic of kosher grasshoppers is that they sometimes swarm.^[6][7] The Ohr Hachaim writes that the communities that ate locusts had been plagued by them every two or three years when they would come and devastate the crops.^[8] This would also explain why eating locusts was not considered a delicacy but used more by the poor ^[9] and accord with the ruling that that one is only allowed to eat a specific permitted type of locust only if there is a "continuous tradition" that affirms that it is Kosher. It is not enough that the locust seems to conform to the criteria mentioned in the Torah.

In Yemen, the locust and the grasshopper share the same Arabic name, although Jews in Yemen recognize the differences between the two.^[11]

Pair of desert locusts (Schistocerca gregaria)

In spite of the reference of other edible locusts in the Pentateuch, such as the Chargol(Aramaic: ניפול‎, Nippul; Arabic: الحرجوان‎, Al-Harjawaan), and the Sal'am (Aramaic: רשון‎, Rashona; Arabic: الدبا‎, romanized: Al-Daba), the tradition of recognizing and eating these specific kinds had been lost in Yemen, prior to their emigration from Yemen in the mid-20th century CE.^[12]

Only certain species of the Chagav (grasshopper) were still eaten in Yemen, such as the species now known as the greyish or brownish Egyptian locust (Anacridium aegyptium), thought by some to be an edible grasshopper,^[13] even though it was known in Arabic by its generic name al-Jaraad (Arabic: الجراد‎),^[14] the Desert Locust, and the Migratory Locust (as quoted from Rabbi Yitzhak Ratzabi).^[15][16]

In 1911, Abraham Isaac Kook, the chief rabbi of Ottoman Palestine, addressed a question to the rabbinic Court at Sana'a concerning their custom of eating grasshoppers, and whether this custom was observed by observing their outward features, or by simply relying upon an oral tradition.

The reply given to him by the court was as follows: "The grasshoppers which are eaten by way of a tradition from our forefathers, which happen to be clean, are well-known unto us. But there are yet other species which have all the recognizable features of being clean, yet we do practice abstaining from them.

[Appendage]: The clean grasshoppers (Hebrew: חגבים‎) about which we have a tradition are actually three species having each one different coloration [from the other], and each of them are called by us in the Arabian tongue, ğarād (locusts). But there are yet other species, about which we have no tradition, and we will not eat them. One of which is a little larger in size than the grasshoppers, having the name of `awsham. There is yet another variety, smaller in size than the grasshopper, and it is called ḥanājir(katydids)."^[17][18]

The Jews of Yemen did not follow the halakhic ruling of Maimonides, where it was made sufficient to merely recognise their features before eating them.^[19] Instead, they ate only those locusts that they acknowledged in their own tradition as being edible, namely, the desert locust (Schistocerca gregaria), and which they called in Yemenite Jewish parlance, ğarād.^[20]

https://en.wikipedia.org/wiki/Kosher_locust#Yemenite_tradition

Context: This is from a Wikipedia article about kosher locusts.

The Jews from Yemen (and Morocco, Algeria, and Tunisia) have a long-standing tradition which allows them to identify which species is the Biblical “Chagav” (thus meeting the requirement in the Shulchan Aruch, and probably satisfying Rashi also). Even if eating insects would be a cheap form of protein, who would Jewish law permit it to today, assuming other forms of protein were available?

The Rules for Mixing Meat and Milk

Context: This is from the Biblical Book of Deuteronomy, right after the reiteration of the dietary laws from Leviticus. It is is the 3rd instance of “You shall not boil a kid in its mother’s milk” (the others being Exodus 23:19 and 34:26).

Why might the Torah want to outlaw boiling a baby goat in the milk of its mother?

Context: This is from the Babylonian Talmud, Masechet (Tractate) Chullin. It assumes that the Torah doesn’t reiterate things unnecessarily, and thus each instance of “Don’t boil a kid in its mother’s milk” must mean something different.

Assuming that one wants to make “a fence around the Torah” to prevent breaking of actual rules in the Torah, what might be the logical progression from not boiling a kid in its mother’s milk to not eating milk and meat together at all?

Context: This is from Mishnah Chullin. It tells us that you can’t cook or eat meat and dairy together, and that to be on the safe side, you shouldn’t have them on the same eating table. However, some foods are considered “pareve”, so you can have them with meat or dairy - anything not explicitly meat or dairy (like fruits, vegetables, and nuts) falls into this category.

Can you have fish with dairy? What about chicken?

Context: This is from the Gemara of Chullin, commenting on the mishnah.

Why can’t you eat chicken with dairy? Would the same concern apply to eggs?

Context: This is from the Shulchan Aruch. It basically says that after eating dairy, one needs to wash your hands (or visually examine them if there’s enough light) and rinse out the mouth before eating meat. The thinking is that dairy and meat shouldn’t mix in the stomach even, but that dairy gets processed super-quickly.

If the goal is to not mix meat and dairy foods, how long would you wait after dairy before eating meat?

Context: This is from the Issur v’Heter l’Rabbeinu Yerucham, a text from the 1300s regarding dietary laws. Based on rabbis in the Talmud who would eat meat at one meal and then dairy at the next, it suggests that 3 hours is enough time to wait. Sephardic Jews (and some Ashkenazim) wait 6 hours. Dutch Jews wait 1 hour. Largely, this is based on different interpretations of what it means to wait between one meal and the next. Given that the iron in meat interferes with the absorption of calcium in dairy, it is advantageous to one’s health to wait between eating meat and dairy, although that fact was presumably not known to the rabbis of the Talmud.

How might it benefit one’s character to have to wait between meat and dairy?

The Rules for Kosher Slaughter

Context: This is from Deuteronomy; we’ve seen this text already as a source for not mixing meat and milk.

If one of the goals of Kashrut is a reverence for life and an awareness that eating meat requires eating another previously-alive animal so that you can live, why would it be important to not eat an animal that has died on its own? For that matter, what might be the health benefits of this?

Kosher slaughter

[T]here is a specified ritual of slaughter by which [birds] must be killed. This method of shechitah involves cutting the jugular vein and the esophagus with a perfectly sharpened knife (i.e. totally smooth edge, clean, instant strike, not a tearing gradual motion). The knife slash cuts off the flow of blood (and air) to the brain causing instant loss of consciousness. In other words, the bird must be put to death swiftly and painlessly. If the bird dies by beating, wounding, crushing, etc. then its death is slower and its suffering greater and it is not permissible to eat it. The process of Kashrut minimizes death and suffering - thus upholding the preciousness of life even in the face of eating meat.

….

[W]ith animals [there] is the [also] requirement of shechitah to insure a swift, painless death.⁹ Since cattle and larger animals are more difficult to slaughter, hoist and shackle treatments were developed to hold the animals down. Some of these procedures were painful and harmful to animals so kosher slaughterhouses changed over to holding pens which are more humane. Some fundamentalist Orthodox slaughterhouses were slower to make these adaptations, leaving some stain on the reputation of kosher slaughter. Nevertheless, the kosher slaughter laws clearly are intended to respect animal life and minimize its pain.

- Yitz Greenberg

https://www.sefaria.org/sheets/311737?lang=bi

Context: This is a D’var Torah given by Rabbi Yitz Greenberg for Parashat Shmini (which talks about the rules of Kashrut), 2021.

Why might Jewish law be so concerned with making sure that animals are killed humanely?

Hechshurs - Kosher Certification

Context: This is from the Babylonian Talmud, Masechet (Tractate) Shabbat, which is about Shabbat. It comes from a discussion about the materials one can use to make Shabbat candles and then how this is different what what is permissible to use for Chanukah candles. This Talmudic story is the first instance that we have of “the miracle of the oil” - it does not appear in any of the contemporary accounts of the Chanukah story, which you would think would have recorded a big deal like this.

What would be the function of the High Priest’s seal on the olive oil jars?

History of Hechshers

Seals

The Babylonian Talmud cites an early example of a kashrut seal: the seal of the Kohen Gadol on jugs containing olive oil used in the Jewish Temple for the lighting of the Menorah.^[2] The Menorah has since become a symbol for purity in Jewish tradition.

LMLK stamp; Redondo Beachcollection #22

'LMLK seals' (bearing the Hebrew letters למלך, equivalent to LMLK) were stamped on the handles of large storage jars mostly in and around Jerusalem during the reign of King Hezekiah (circa 700 BC), based on several complete jars found in situ buried under a destruction layer caused by Sennacherib at Lachish.^[3] None of the original seals have been found, but about 2,000 impressions (also referred to as stamps) made by at least 21 seal types have been published.

The practice of marking food as a sign of kashrut can be dated back as far as the 6th century CE. A clay stamp bearing a Menorah image from this period was discovered in an excavation near Acre, Israel in 2011. According to archeologists, local Jews stamped their dough with Menorah impressions while preparing bread, in order for consumers to verify its kashrut.^[4]

Certification

An 11th-century certificate found in the Cairo Geniza written by a rabbinical court, testified the kosher status "according to rabbinic law" of the cheeses being sold by a Karaite grocer, Yefet b. Meshullam of Jerusalem. The document explains that the cheese was produced in a factory on the Mount of Olives that followed rabbinic practice. The certificate reads: "The cheeses are kosher and it is appropriate for Rabbanite Jews to purchase them. We grant this permission only after having made a formal purchase from him and having witnessed an oath he took on the holy Torah." While Karaite and Rabbanite communities in this period were theologically at odds, they often maintained good social and economic relations. It was obviously as important for the Karaite grocer to do business with Rabbanite customers as it was for the latter to be able to rely on the religious acceptability of his products.^[5]

https://en.wikipedia.org/wiki/Hechsher#History

Kashrut Certification Agencies

Before the advent of industrially-produced foods, Jewish families prepared their own meals at home and ensured the kashrut of raw ingredients themselves by taking chicken and meat to be slaughtered by a reliable shochet and ensuring that milking was supervised by a Jew. In the kitchen, the housewife observed the strict separation of milk and meat. It was only in the 20th century, with the increased availability of industrially-produced food products aimed at the Jewish consumer, that independent kosher certification became a necessity.^[12][13]

The first independent kosher certification agency was founded by the Orthodox Union (OU) in 1924. Its director, Abraham Goldstein, left Orthodox Union Kosher to establish a second certification agency, OK Laboratories, in 1935.^[14][15] Kosher certification expanded in the 1930s as major brands such as Coca-Cola sought certification to expand their market.^[16] The proliferation of factory-produced foods following World War II saw a concomitant rise in kosher certification. In 1950, for example, the OU's staff of around 40 mashgichim (rabbinic field representatives) certified 184 products for 37 companies; by 1972, the OU had more than 750 mashgichimcertifying over 2,500 products for 475 companies.^[17]

In the late 20th century, the increasing use of pre-processed ingredients – such as artificial flavorings, emulsifiers, and preservatives – further broadened the scope of kosher certification. A product produced in one country can contain ingredients and flavorings produced in other countries; these ingredients and flavorings must be tracked to their point of origin to verify their compliance with kashrut laws. According to a 2013 estimate, the 135,000 food products then certified kosher contained more than one million food additives.^[18] Certification agencies regularly send mashgichim to factories in China, Thailand, and the Philippines to oversee the production of pre-processed ingredients and ensure their kosher status.^[16] Many certification agencies accept the use of pre-processed ingredients that have been approved by other agencies.^[19]

Certification agencies may differ on the kosher status of foods based on the p'sak (halakhic ruling) of their rav hamakhshir (rabbinic authority). For example, aspartame, a key ingredient in Diet Coke, is considered to be kitniyot by the Kashruth Council of Canada(COR) and therefore that agency does not give its hechsher to that product for use on Passover. In contrast, the OU relies on poskimwho rule that the additive is kitniyos shenishtanah–kitniyos that has been "changed at the molecular level" (and therefore is no longer kitniyos)–and therefore the OU gives its hechsher to Diet Coke for use on Passover.^[20]

^{https://en.wikipedia.org/wiki/Kosher_certification_agency#History}

Context: These Wikipedia articles shows the history of hechshers.

Why would it be helpful to have a seal of approval on food (and cleaning supplies for dishes and tablecloths) that meet Jewish dietary standards?

The Rules for Kosher Wine

Context: This is from the Babylonian Talmud, Masechet (Tractate) Avodah Zarah, which is about idol worship. The text suggests that there are three types of wine which Jews shouldn’t drink: 1. Wine meant for idolatry. 2. Non-Jewish wine not intended for idolatry. 3. Wine of a Jew which has been left for safe-keeping with an idolator, who might switch it with wine meant for idolatry. One of the concerns is that if one drinks the wine of non-Jews, one might be partaking of wine which has been intended for the worship of idols, and thus drinking the wine of non-Jews would really be committing idolatry.

Given that Christian sacramental wine is not available to everybody people (Jews or non-Jews), is this concern still an issue?

Context: Also from Avodah Zarah. The argument in this text is that drinking wine with non-Jews will lead to inter-marriage, and inter-marriage will lead to leaving Judaism (both for yourself and certainly for your children).

Given the high rates of inter-marriage today, should there be a greater insistence on only drinking Kosher wine (i.e. only made by Jews), or will that not make a difference?

Context: More Avodah Zarah. There was a concern that even kosher wine which had been served by non-Jews might have been first offered to an idol before being brought out. However, the Talmudic rabbis noticed that wine which had been brought to a boil during its preparation (which is called “yayin mevushal”) was not used for idol worship, so they permitted it even if it had been served by non-Jews (also see Kitzur Shulchan Aruch 47:3). For example, Bartenura Moscato is “mevushal”.

Why might a winemaker who is concerned about the maximum number of people buying their wines choose to make a “mevushal” wine?

Context: More Shulchan Aruch. This time it’s the “gloss” of Rabbi Moses Isserles, giving the Ashkenazi take on Rabbi Caro’s Sephardic text. For more on the kashrut of wines, see https://www.rabbinicalassembly.org/sites/default/files/assets/public/halakhah/teshuvot/19861990/dorff_wines.pdf.

According to this text, is there any problem with a non-Jew serving wine?

The Rules for Kosher Dairy

Kosher Cheese

The controversy over the kashrut of cheeses is an old one, dating back to the time of the Talmud (Mishnah Avodah Zarah 2:4-5, Mishnah Chullin 8:5, Chullin 116b). Cheese is made from curdled milk. Since the curdling agent was rennet, which is extracted from the walls of a calf’s stomach, cheese was forbidden as a mixture of dairy and meat. According to some authorities, however, the use of rennet does not affect the kashrut of cheese because rennet no longer has the status of food and instead is comparable to a mere secretion (pirsha b’alma). This controversy appears again and again among the poskim (see Rabbenu Tam in Avodah Zarah 35a, s.v. חדא קתני; Maimonides Hil. Ma’akhalot ‘Asurot 4:13, 14, 19; ‘Aruch Hashulchan Y.D. 87:42). Some halachic authorities demand a hechsher for certain cheeses, implying that those without a hechsher are not kosher; other authorities maintain that all cheeses are permissible and no hechsher is necessary.

The Committee on Law and Jewish Standards of the Rabbinical Assembly has decided to follow the lenient opinion. First of all, it reasons, the chashashot, fears expressed by those who require a hechsher applied only in former times, when cheesemaking was a cottage industry and there was no way to control the ingredients used. Under these conditions, there was always the dancer that an individual farmer who made cheese might use the milk of a non-kosher animal or might add lard to the mixture. Today however, at least in America, cheesemaking is a major industrial enterprise regulated by the Pure Food and Drug Law, which requires that most food products bear a label listing their ingredients.

Furthermore, the rennet used in many of the hard cheeses does not impair their kashrut, both for the Talmudic reason stated above and also because the substance from which the rennet is extracted is thoroughly dried and treated with strong chemicals, and this process makes the rennet a D’var Chadash (new substance) or comparable to a piece of wood (eitz b’alma). Thus, all cheeses that are subject to the Pure Food and Drug Act should be considered kosher.

- Rabbi Isaac Klein

Context: This text is from Rabbi Isaac Klein’s A Guide to Jewish Religious Practice (I979). He basically argues that cheese (and gelatin) is not a problem because the curdling agent, rennet, has been processed so much that it is “something a dog wouldn’t eat” (which is a halachic test of whether something counts as food), so even if it came from an animal it shouldn’t be a problem. That being said, he doesn’t say anything about regular cheese being kosher for Passover, so just like you might want to use kosher wine at the seder, you might want to use kosher cheese for your matzah pizza.

Does the argument that “In America we know what’s in our food so there’s no concern about lard in cheese” work for you?

Honey

Context: This is from the Mishnah, Masechet (Tractate) Bechorot, which is about the special rules of firstborn animals. The Mishnah says that if a donkey has an offspring that looks like a horse, then it’s exempt from the rules of firstborn animals. The Mishnah then goes on to say that if a cow has an offspring that looks like a donkey then it’s still kosher to eat, because of the rule in our text.

If bees aren’t kosher, should honey be treif under this rule?

Context: This is from the Babylonian Talmud, Masechet (Tractate) Bechorot, which is about the rules of firstborn animals. This text is commenting on the text from the Mishnah, trying to understand the implications of it. The answer is that bees are storing the nectar but not digesting it, so it doesn’t really count (see here for a good explanation of how bees make honey: https://news.ncsu.edu/2013/06/how-do-bees-make-honey/). Also, for the record, human milk is kosher even if humans aren’t kosher animals. This stems from a time before infant formula and a desire not to legislate Jews into extinction.

What are some ways that honey could symbolize Judaism?

Extra Stringencies

Cholov Yisroel / Cholov Stam: Cholov Yisroel refers to milk or dairy products that have been under constant rabbinic supervision from the time of milking the cows until the completion of production and packaging the product. In countries where there is strong government oversight of the dairy industry, most kosher certifying agencies will certify dairy products without constant rabbinic supervision. This is permitted by many rabbinic authorities (cholov stam). Some kosher consumers will only eat, or prefer, dairy products that conform to the cholov Yisroel standard. Kosher certifying agencies will provide this certification in addition to standard kosher dairy certification. Products certified as kosher are assumed to be cholov stam unless specifically labeled as cholov Yisroel.

Glatt Kosher: "Glatt" means "smooth." Technically, this refers to the lungs of a kosher slaughtered animal being free of any adhesions and therefore on higher kosher level than non-glatt. Nowadays most Orthodox Jews only accepts glatt kosher meat. It has come to be used in the vernacular to refer to any kosher item that is of a "higher standard."

Pas Yisroel: Bread or pastry products that a rabbi has assisted in baking either by lighting the fire, putting the food on the fire, or adding heat to the fire.

Yoshon: Products made from any of the five grains that have grown, or at least taken root, prior to the preceding Passover.

https://www.kof-k.org/AboutUs/KosherGlossary.aspx

Context: There are extra stringencies that some Jews take on - for instance dairy must be “Cholov Yisroel”, bread must be “Pas Yisroel”, or meat must be “Glatt kosher”. Additionally, some Jews (general Lubavitch) only eat meat slaughtered by somebody from Chabad. For instance, Milts BBQ for the Perplexed in Chicago only serves Glatt Kosher meat, but they have a “Lubavitch Patty” as an option for all of their hamburgers.

What would be the pros and cons of holding by these stringencies?

A Recap of the Basics

With appreciation to Sarah Zollman, Wikipedia, Yitz Greenberg, Benjamin Adler, R. Kalman B’Simcha, and Miriam Camerini.

Appendix: Dishwasher Issues

Teshuva on Dishwashers from the Committee on Jewish Law and Standards

YOREH DEAH 95:20151
On the Kashrut of Dishwashers
Rabbi Loel M. Weiss
The following teshuvah was approved by the CJLS on November 11, 2015 by a vote of nine in favor, four opposed, and eight abstaining (9-4-8). Voting in favor: Rabbis Pamela Barmash, Miriam Berkowitz, David Booth, Elliot Dorff, Baruch Frydman-Kohl, Jeremy Kalmanofsky, Jonathan Lubliner, Micah Peltz, Paul Plotkin. Voting against: Rabbis Aaron Alexander, Reuven Hammer, David Hoffman, Amy Levin. Abstaining: Rabbis Noah Bickart, Joshua Heller, Susan Grossman, Adam Kligfeld, Gail Labovitz, Daniel Nevins, Avram Reisner, Jay Stein.

Sh’ayla (Question):
May a non-Kosher Home Dishwasher be Kashered?
May a Home Dishwasher be Kashered for Passover?
May a Home Dishwasher be used to wash meat and dairy dishes? Simultaneously? Consecutively?

Teshuvah (Answer):

How a Dishwasher operates

This Teshuvah only deals with home dishwashers where hot and cold water enter the dishwasher separately.

A general overview of how a dishwasher operates is helpful to understanding the kashering process.²

In a home dishwasher³ hot and cold water enter the tub separately. In a normal dishwashing cycle, the water is kept at a temperature of 120-140 degrees Fahrenheit. The water collects at the bottom of the tub but does not cover the dishes. A pump then circulates the water through holes in the rotating arms, which sprays the water onto the dishes. While this is being done the detergent is released into the tub and is sprayed over the dishes. Dirt from the dishes is disposed of at the bottom of the tub. Depending on the model, larger pieces of food are either ground up and sent through the drain or are collected in a filter that needs periodic cleaning.

Since the mid 1990s all dishwashers made for home use in America have a tub made of stainless steel, plastic or a hybrid combination of both. Before the 1990s, dishwashers were also made of porcelain.

Over time, these porcelain dishwashers had a tendency to chip or crack. Therefore this Teshuvah will only concern itself with metal or plastic dishwashers. ⁴

Recently a new type of dishwasher, a ‘drawer dishwasher’ has come onto the market. This dishwasher operates with two different drawers that can be used separately or simultaneously.⁵

Halakhic Concerns Kli Rishon/Kli Sheni:

A kli rishon is a vessel in which cooking is done. A kli sheni is a vessel into which food is placed from the original pot that was used for cooking. This is an important distinction because of the accepted principle (Shulhan Arukh YD 105:2) that a taam (a taste/flavor, see below) cannot be transferred in a kli sheni.

There are at least 4 reasons to be mekeil (lenient) and consider the dishwasher a kli sheni.
1. The hot water is heated in a hot water heater (kli rishon), then a tube draws the water to the dishwasher, finally the water pours into the dishwasher itself.
2. The water sprayed into the dishwasher is iruy shenifsak ha’kiluach (pouring that is
interrupted)⁶.
3. Any water that may gather at the bottom of the dishwasher never completely covers the dishes.

4. According to some opinions, the water never reaches the temperature of yad soledet bo (a hand can’t stay in it).⁷

B’ayin/Taam:
Another concern is whether there are any actual pieces of foodstuffs (b’ayin) on the dishes or is it the taam (taste/flavor) that is in the dishes.

Concerning b’ayin, modern dishwashers are constructed so that any foodstuff is sent to the bottom of the dishwasher where the filter either disposes of it or captures it inside the filter.⁸

Concerning taam, the normative Halakha is that by waiting 24 hours (ben yomo⁹) any taam is made pagum (unfit as food). In addition, we have an added leniency since the Shulhan Arukh (YD 95:4) rules that soap in the dishwasher will render the taam as pagum.¹⁰

Another Halakhic issue is whether the taam comes from a non-kosher source or a kosher one. If it is from a kosher source then the concept of notain taam bar notain taam de’heteira¹¹ applies. This means that no prohibited taam is transferred from one vessel to another vessel. If, however, the taam is from a non-kosher source then the taam is de’issura and is transferred.

Having dealt with how a dishwasher works and the Halakhic issues involved, we can now deal with our questions.

May a non-Kosher Home Dishwasher be Kashered? May a Home Dishwasher be Kashered for Passover?

Metal and Plastic are both materials that, if they can withstand the heat necessary for kashering, may be kashered.¹² Dishwashers come in contact with food particles through hot water, so they should be kashered with hot water (hag’alah). While the generally accepted principle is that hag’alah (kashering by water) requires boiling water (212 F), this is not necessarily true. The Mishnah Berurah (Shaar Hatziyun 451:196) says that the rule of kevol’o kach polto¹³ means that each utensil is kashered with water that is as hot as the water that it uses.

Therefore, by thoroughly cleaning the dishwasher, then waiting 24 hours and running it at its highest temperature, metal and plastic dishwashers can be kashered from non-kosher to kosher and from hametz to Passover.

May a Home Dishwasher be used to wash meat and dairy dishes? Simultaneously? Consecutively?

Since we consider a dishwasher a kli sheni, we do not concern ourselves with cooking. Furthermore, as we said above, the foodstuffs are removed from the tub of the dishwasher. Finally, the taam is de’heteira.

The one concern we have is the racks where the dishes are placed. Rabbi Moshe Feinstein, in his Teshuvah permits using a dishwasher for meat and dairy but requires that the racks be changed. However, we can rely on the principle of noten taam li’fgam that after 24 hours (ben yomo), the taam is pagum¹⁴ and the additional safeguard (b’dieved), that the soap also makes the taam pagum, and therefore we do not require separate racks.

Psak (Ruling):

1. Dishwashers made for residential use, whether metal or plastic may be kashered from treife to kosher and from hametz to Passover. The procedure is as follows:
The dishwasher should be thoroughly cleaned paying special attention to the filter and the silverware rack.
The dishwasher should not be used for 24 hours.
The dishwasher should be run one time at the highest temperature with soap in the soap dispenser and in the main dishwasher.

2. The dishwasher may be used to wash meat and dairy dishes consecutively. While we do not require new racks, we do require waiting 24 hours between using the dishwasher for meat and dairy dishes.¹⁵ However, if for some reason the dishwasher was used without the 24 hour waiting period, then b’dieved, we can rely on the soap rendering the taam pagum and the dishes are still kosher. It is strongly suggested that if there is a filter that requires manual cleaning at the bottom of the dishwasher, it be checked to assure there are no pieces of food remaining at the bottom. Also, the silverware rack must also be checked for food residue.

3. Dishwashers may not be used to wash dairy and meat dishes simultaneously.

4. With the new ‘drawer dishwasher’, if one designates one drawer exclusively for meat vessels and the other drawer exclusively for dairy, then the dishwasher may be used to wash both drawers simultaneously.

¹ I want to thank Rabbis Aaron Alexander, Avram Reisner and Paul Plotkin for their insights and suggestions. I especially want to thank Rabbi Plotkin for permission to use many of the definitions of Halakhic terms from his Teshuvah, “Pizza from a Non-Kosher Establishment” that was approved by the CJLS in 2012.
² A good video of the standard operation of a dishwasher can be found at http://www.repairclinic.com/RepairHelp/Dishwasher-Repair-Help
³ This Teshuvah does not address dishwashers that fill with only cold water and then a heating element inside the dishwasher heats the water.

⁴ Rabbi Moshe Feinstein, Iggerot Moshe, YD 3:28-29, YD 2:46 rules that if one purchases a home containing a non-kosher porcelain dishwasher, the dishwasher may be kashered by waiting 12 months and then running a soapy cycle, 3 times. He does not permit kashering a porcelain dishwasher for Passover, OH 3:58.
⁵ Based on discussions with Fisher-Paykel, the manufacturer of most of these types of dishwashers on the market, it is clear that both drawers are totally separate, so that each drawer can be considered a separate dishwasher.
⁶ Rashbam cited in Tosafot, Shabbat 42b says that any iruy is iruy kli sheni. Rabbeinu Tam disagrees, but both agree that if the iruy is interrupted then it is considered an iruy kli sheni.
⁷ There are different opinions among Posikim as to what constitutes yad soledet bo. Rabbi Paul Plotkin, op cit, “Yad Soledet Bo: This is the minimum temperature at which cooking takes place according to halakha and that taste is transferred...Authorities have offered a range of 110 to 175 F.”
⁸ “Consumer Reports”, in its November, 2014 issue, recommends NOT rinsing dishes before they are placed in the Dishwasher. They claim that it is both a waste of water and not necessary because modern dishwashers do a very effective job of removing pieces of food and sending them out of the dishwasher tub.

⁹ Shulhan Arukh YD 103. Rabbi Paul Plotkin, op. cit., “According to halakha, taste which is absorbed into the walls of the pot remains fresh for 24 hours. After that time, the taste is considered distasteful (pagum) and can no longer render food subsequently cooked in the pot as prohibited.”
¹⁰ The Taz and the Shakh (YD 95, 21) say there is no valid basis for this ruling.
¹¹ Rabbi Paul Plotkin, op. cit., “Notain Taam bar Notain Taam De’heteira, refers to the infusion of permissible taste into a vessel followed by that taste being infused into another food. When the taste of the permitted food is cooked into a vessel and subsequently discharged into another food the secondary taste is not capable of producing a prohibited entity.”
¹² Rav Henkin (Am HaTorah, Cycle 1, Volume 10, page 5), Tzitz Eliezer (4:6:3) and Minchas Yitzchok (3:67) are all authorities who permit the kashering of plastic.
¹³ Rabbi Paul Plotkin, op cit, “This means that the way in which something is absorbed is the way in which it is expelled.”

¹⁴ See Footnote 9, above.

¹⁵ If racks are changed for meat and dairy, then there is no obligation to wait 24 hours. The dishwasher can be used immediately.

The Committee on Jewish Law and Standards of the Rabbinical Assembly provides guidance in matters of halakhah for the Conservative movement. The individual rabbi, however, is the authority for the interpretation and application of all matters of halakhah.

https://www.rabbinicalassembly.org/sites/default/files/assets/public/halakhah/teshuvot/2011-2020/weiss-dishwasher.pdf