Sous Vide Cooking and Kosher Law FAQ

Frequently Asked Questions Sous Vide and Jewish Law

Sous vide, a vacuum-sealed slow cooking method developed by French chefs, is now becoming popular among home cooks, including many Jewish homes. Many people are now starting to wonder, what are the halachic (Jewish legal) ramifications of this method of cooking?

For example: can a sous vide be used for meat and milk, or meat and fish (since the food is vacuum sealed)? Can you use your sous vide machine on Passover if you’ve used it during the year? Does a sous vide machine need tevila? Can you use a sous vide machine on Shabbat or Yom Tov and if so, what are the issues and concerns?

These questions aren’t answered directly in classic Jewish works since the cooking method is new, but the halachic principles can be applied to find out the answers of how to use a sous vide machine in a kosher home.

Below, the rabbis of the OU (the largest kosher certification agency in the US) have shared the answers to the most common questions they get about sous vide.

About Sous Vide Cooking

What is sous vide? Sous vide, which means “under vacuum” in French, is a method of cooking in which food, such as meat or fish, is placed in a vacuum-sealed plastic pouch and immersed in a pot of water at a precisely regulated temperature. In this manner, foods can cook at a low temperature (typically 130-140 degrees Fahrenheit) for many hours – at times, up to 48 hours. The intent of this method is to maintain consistency, and to evenly cook the food inside without overcooking the outside. It also seals in the juices. (Note: Sous vide cooking might not meet minimum cooking temperatures of health departments for restaurants, catering, etc.)

Does a sous vide machine require tevilat keilim?

There are two parts to a sous vide machine: a water bath tub and a thermostatically controlled immersion heating element that also circulates the water. The pot, if made from metal or glass, requires tevila, even though the food is cooked inside a plastic bag. However, Rav Belsky, zt”l held that the immersion heating apparatus does not require tevila. This is because the immersion heater does not function as a utensil, but rather as a source of heat, like a burning coal.

May a sous vide machine be used with both dairy and meat items?

No, it may not. Although the foods placed in the machine are first sealed in plastic, halachically, the taste of the food leaches through the plastic into the water (see Yorah Deah 92:5). Teshuvot Har Tzvi (Yorah Deah 89) discusses a similar question relating to placing dairy and meat pots on a steam table. He writes that not only may one not place the pots into the hot water bath at the same time, but even if one changes the water in between uses, it may not be done.

It would therefore follow that a sous vide machine should be designated as dairy or meat, but it may not be used interchangeably, even if one changes the water.

May a meat-designated sous vide machine be used with fish? If so, can I cook fish and meat in the machine at the same time?

Some have the custom, in accordance with Tur’s position, to keep separate pots and utensils for meat and fish. One who follows this custom should have separate machines for fish and meat as well. However, the more common custom, cited by Taz (Yoreh Deah 116:2), is to permit using the same utensils for fish and meat, so long as they are clean.

The question arises whether one is permitted to cook meat and fish, each sealed in plastic, in a sous vide at the same time. It would seem that there is a basis to permit this as well. Rav Belsky, zt”l held that one may eat an onion cut with a designated-meat knife together with fish. Although an onion cut with a meat knife is considered to be “fleishig,” it is still not actual meat. The sakana (danger) of eating fish and meat together only applies if one mixes actual meat with fish. Although fish cooked at the same time as meat in a separate pouch would be considered fleishig, it is not actual meat.

Nonetheless, since the plastic bags may leak, it is not recommended to cook meat and fish simultaneously. If one changes the water between uses, one may cook fish after meat.

May a year-round sous vide machine be used on Passover if I am sure I only put meat, fish or vegetables inside the machine? Also, may one kasher for Passover a sous vide machine used with chametz?

If one used a sous vide machine with chametz, it definitely requires kashering. Even if one feels quite certain that their machine was only used with non-chametz items, the custom is that we do not use appliances that sat out on our chametz counters during the year without kashering first. At some point during the year, hot chametz might have fallen against the machine, or some chametz item might have been cooked in the machine that one no longer recalls. Therefore, the machine should not be used on Passover without kashering.

Regarding kashering a sous vide machine, there are two parts to the apparatus: the water bath (pot) and the heating element. One may not kasher a utensil unless all sections are accessible and it can be scrubbed clean. Since the heating mechanism has a fan and narrow areas that are difficult to access, it should not be kashered (see Mishnah Berurah 452:31). The pot can be kashered following the regular rules of hagala. If the pot is plastic, there are differing opinions as to whether one may kasher it for Passover. A sous vide unit can be kashered for year-round use. However, if a ceramic pot was used, that can never be kashered.

Is there a concern of hatmana (insulating) in leaving food in a sous vide machine on Shabbat?

Shulchan Aruch (Orach Chaim 257:8) rules that it is prohibited to insulate food and place it on a fire before Shabbat. Even if everything is performed before Shabbat, this is included in the prohibition of hatmana, which is restricted because it might lead to adjusting the fire on Shabbat. Accordingly, it would seem that one may not use a sous vide machine over Shabbat, since the food is wrapped inside a plastic pouch and submerged into hot water that is still being heated on Shabbat.

However, Sefer Pitchei Teshuvot (258:3:25) cites many poskim (e.g. Sefer Az Nidberu, Rav Shlomo Zalman Auerbach, Teshuvot V’hanhagot) who permit this type of activity if the intent of the pouch is not to insulate, but rather to protect the taste and keep the foods separate.

According to this view, one may use a sous vide machine over Shabbat. Others follow a stricter view and do not use a sous vide machine for Shabbat. This concern would not apply on Yom Tov.

May one remove food from a sous vide machine on Shabbat?

At times, it is permissible. Sous vide machines are calibrated to the tenth of a degree, and are very sensitive to changes in temperature. Even so, removing a bag of food from the water does not seem to affect the temperature. One should also be aware that many of these machines have a safety feature that will turn off the machine if the water level drops below a certain point. It is recommended that one experiment before Shabbat to ensure that removal of the pouches will not affect the machine. If one wishes to be extra careful, one may set their machine to turn off before the food is removed.

I have a sous vide machine that is set to 112 degrees Fahrenheit. Can I place food into the machine on Shabbat to warm up the food?

According to most opinions 112 degrees Fahrenheit is less than yad soledet bo (the minimum temperature required for cooking). Many follow the ruling of Rav Shlomo Zalman Auerbach, zt”l that the temperature of yad soledet is certainly not less than 113 degrees Fahrenheit. Some hold that it is not less than 120 degrees Fahrenheit. Therefore, putting food into a machine set to 112 degrees Fahrenheit would not be a concern of cooking or returning food to a fire on Shabbat.

However, since the food is cold, adding it to the sous vide will almost certainly activate the heating mechanism or cause a change to the digital readout. As such food may not be added unless the machine is turned off. However, if the machine is off, one may place cold packaged foods in the water to warm up. This is not a concern of hatmana (insulating food which is prohibited in certain circumstances), which would not be permitted on Shabbat, since both the food and the water are below yad soledet (halachically cold).

For those who allow using a sous vide machine on Shabbat, is it permissible to put food in a sous vide machine before Shabbat if it will not be ready until Shabbat morning?

This question relates to the prohibition of shehiya (leaving food to cook on Shabbat). Shehiya is prohibited because a person may forget it is Shabbat and hasten the cooking process to make sure the food is ready for Shabbat evening. There is a talmudic dispute whether shehiya is restricted on food that is already half-cooked (which is somewhat edible) before Shabbat.

Beit Yosef (Shulchan Aruch, Orach Chaim:253) follows the strict opinion and prohibits shehiya unless the food is fully cooked and further cooking will be detrimental, while Rema rules leniently. Sephardim, who follow the Beit Yosef, may not place partially cooked food in a sous vide before Shabbat. Ashkenazim follow Rema, and may do so if the food is half-cooked or more. Nonetheless, the Mishnah Berurah (Beiur Halacha, 253 s.v. “ela”) recommends that even Ashkenazim should preferably follow the stringent view of the Beit Yosef, even if the food is more than half cooked.

One way to alleviate the concern of shehiya is by placing a blech (covering) over the fire. The blech serves as a reminder that the fire cannot be adjusted on Shabbat. In the case of an immersion heater, it is not possible to cover the source of heat. In such a case, some poskim permit covering the controls instead of covering the heat-source. If one follows the lenient view and covers the controls, it is preferable that the food should be at least half cooked before Shabbat.

Another approach to avoid the prohibition of shehiya is to only place raw meat into the sous vide just before Shabbat. Since the meat is raw, it is clear that the food is not intended for consumption until the next day and there is no reason to tamper with the fire in the evening to hasten the cooking process.

Shehiya is only a concern for Shabbat. The prohibition of shehiya does not apply on Yom Tov.

Credit: OUKosher.org Halacha Yomis program. Sign up at the link to receive emails of a halacha a day on topics similar to this.

The kashrut content of this article was reviewed for accuracy on January 28, 2024 by Rabbi Eli Gersten.