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Can a sous vide be used for Shabbos? What is the correct way to do it? We are thinking about making something in place of Cholent for Shabbos day.

 

It may not be used on Shabbos, but is permissible for use on Yom Tov.

An excellent comprehensive article about Sous Vide for Shabbos has been written by Horav Shmuel Lesches, Melbourne, Australia, and appears below (with minor adaptations).

It’s the latest fad in cooking, and with a name like sous vide, who can resist? Sous vide (pronounced su‑vee) is the French equivalent of “under vacuum”; sous vide will cook food uniformly while retaining its natural juices and aroma, achieving results that are impossible through other cooking methods.

How does it work? The food is vacuum-packed in a plastic bag (essentially a Ziploc bag) which is then submerged in a low-temperature water bath. The key factor is for the water to be held at a steady and accurately controlled temperature much lower than what is typically used in cooking, normally between 55‑75°C, depending on the food being cooked. The water is heated with an electronically-controlled heater element and circulated with a fan to maintain perfectly consistent temperature throughout. The cooking duration can last anywhere between half-hour and several days.

To better understand the benefits, let us contrast sous vide with conventional cooking or baking, such as oven roasting or grilling. With conventional methods, the food is subjected to heat much higher than the desired internal cooking temperature. For example, meats and poultry are typically baked or roasted at oven temperatures of 180°C, even though the desired internal cooking temperature is only around 60‑70°C. Therefore, heating needs to be stopped when the centre of the cooked item reaches a few degrees below the optimum temperature, as residual heat at the edges of the item will continue to cook its centre for a little while even after the food is removed from the source of heat. If the food is removed from the source of heat even a little too late, it will be overcooked, whereas if it is removed a moment too early, it will remain under-cooked. Either way, the food will not be cooked evenly; the outside will be more cooked than the inside.

Contrast this with sous vide. Due to precise temperature control, and the fact that the bath temperature exactly matches the desired internal cooking temperature, sous vide cooking can continue until the center of the food has reached its optimum temperature, with the entire piece being cooked evenly and uniformly. Even once completely cooked, the food can remain immersed in the bath for hours without the risk of becoming overcooked, for the food cannot get any hotter than the water it bathes in. This takes the guesswork out of cooking times, and also affords greater flexibility to the chef, who is no longer bound to turn off the source of heat at an exact time.

The use of temperatures much lower than conventional cooking has another important benefit – much higher succulence. For example, the texture of meat softens instead of toughens, and all the natural moisture is retained. With vegetables, where extreme tenderness or softness is generally undesirable, the low temperature of sous vide allows them to be thoroughly cooked while maintaining a firm and crisp texture.

The fact that the food is cooked in a vacuum has practical ramifications for storage purposes – the lack of oxygen allows the sealed cooked food to be refrigerated for considerable times. In fact, this was the original reason for sous vide’s renaissance back in the 1960’s, but its increasing popularity ever since is more attributable to the other advantages described above.

 

Sous vide on Shabbos

Officially, the sous vide method was first described in 1799 by a certain Benjamin Thompson, in an essay artfully titled: “On the construction of kitchen fire-places and kitchen utensils together with remarks and observations relating to the various processes of cookery and proposals for improving that most useful art.” However, his method was all but forgotten or ignored until the 1960’s, when it was initially used industrially, more as an aid to food preservation than anything else. From there, it spread to the kitchens of fine restaurants where the art of sous vide was developed and perfected. Even then, sous vide was almost unheard of in residential kitchens until the mid-2000’s, which is when it began proliferating in homes around the world.

Somewhere along the way, it dawned upon the Jewish world that sous vide might offer the perfect heartburn-free alternative to cholent. Just set up the machine before Shabbos, plonk in some choice chunky slabs of prime rib, and voila! What better Oneg could there be than soft and succulent medium-rare prime steak for Shabbos afternoon lunch?

The notion that there might be Halachic issues with sous vide might initially sound silly. After all, if you could use a crockpot on Shabbos, then you should be able to cook sous vide too, because what’s the difference? Right?

Wrong! There are a number of important distinctions between a crockpot and sous vide. Subtle as they may seem, these differences make a world of a difference in the realm of Halacha. As we will proceed to demonstrate in this article, a whole range of separate concerns need to be dealt with. Taking a lenient approach to sous vide would require one to rule leniently on each and every one of these separate issues, a position which is virtually untenable. The Alter Rebbe certainly rejects a number of these leniencies, and this would negate sous vide on Shabbos for those who follow his rulings.

 

Shehiya: The Blech

The first issue to address is the Rabbinic prohibition of Shehiya. From the Torah perspective, one may place food over an open flame before Shabbos in order that it cooks on Shabbos. Nevertheless, Chazal forbade this due to the concern that a person may come to stoke the fire on Shabbos in order to speed up the cooking process.

One method of avoiding the prohibition of Shehiya is to cover the flames, typically with a Blech. Covering the fire indicates that one does not desire a strong flame, it diverts his attention from the fire, and it serves as a reminder not to increase the flames. However, it is not practical to use a Blech with sous vide, because covering the heating element will prevent it from maintaining the water at the right temperature.

Technically speaking, a heating element is comprised of an inner electrical coil and an outer protective sheath. The inner coil is the source of heat, whereas the outer sheath protects the coil as well as isolates it electrically. Nevertheless, the outer sheath cannot be regarded as a Blech, because its presence is part of the normal way of cooking and does not serve as an indication or reminder. This is true of all other electric heating appliances with variable temperature ranges such as electric cooktops, urns and most crockpots. And it is true for sous vide too.

At this point, we should note that modern “fires” are different than those of Chazal. In the past, the actual flames were not only the source of heat, but its control point. In other words, to increase the heat, one would stoke the actual fire or add fuel directly to it. However, in our times, the control point is generally distinct from the actual source of heat. For example, the typical cooktop is controlled by knobs at the side, as are urns and crockpots. If the actual heating element cannot be covered, is it sufficient to cover the control panel? The (almost) unanimous consensus of contemporary Poskim is that the actual source of heat needs to be covered. It is preferable for the control knobs or panel to be covered as well, either by the Blech itself or by a piece of foil, as an additional precaution against inadvertently raising the heat. Nevertheless, covering the knobs is only an additional and non-obligatory safeguard which cannot substitute for covering the actual source of heat. Since the sous vide heating element cannot be covered, it would not help to cover the control panel instead.

Shehiya: Partly or Fully Cooked Food

At this point, it would seem that sous vide is a no-go on Shabbos. However, it must be noted that a Blech is not always  required. There is a dispute whether the prohibition of Shehiyah applies to foods that are partially or fully cooked. In general, these can be classified in two positions:

1.   Once food is minimally cooked (maachal ben druso’iy), there is no further worry that a person might stoke the flames, because the food is already edible, at least nominally so. What constitutes minimally cooked? Rashi states that this refers to food that is one-third cooked whereas the Rambam maintains that this refers to half cooked food. It is important to note that according to most Poskim, these fractions do not represent time, i.e. a third or half of the time it normally takes to cook. Rather, these fractions are qualitative and are measured against the degree of cooking most people would regard as fully cooked.

2.   Even after food is fully cooked, there remains the concern that one will stoke the flames, unless further cooking is disadvantageous to the food.

The Mechaber (R’ Yosef Caro) is widely (although not unanimously) seen as taking the latter stringent opinion. Thus, for Sephardim, the prohibition of Shehiya always applies unless the food is fully cooked and further cooking is disadvantageous. However, for Ashkenazim, the Ramo (R’ Moshe Isserles) takes the lenient approach. Accordingly, the Alter Rebbe rules that the prohibition of Shehiya applies only to food that is not yet half cooked.

Despite this, best practice dictates that a flame be covered with a Blech even when the food is fully cooked before Shabbos (for a number of reasons beyond the scope of this article). This is indeed the widespread custom, even though it is strictly speaking not always required. Yet, when it is impossible to use a Blech, one may circumvent the prohibition of Shehiyah by ensuring that food is already cooked.

A practical example of this is using an electrical urn on Shabbos. It is not really possible (or advisable) to create a Blech inside the urn to separate the heating element from the water. Neither can the protective sheath surrounding the electrical coil be regarded as a Blech, as we saw above. In the absence of a Blech, the prohibition of Shehiyah is avoided simply by ensuring that the water inside the urn is fully cooked before Shabbos. Even the Mechaber would concede that there is no concern of Shehiyah, because the water is already fully boiled, and any additional cooking that occurs on Shabbos does not enhance the water in any way. In fact, the additional cooking can be regarded as disadvantageous, for it causes some of the water to be lost through evaporation.

Another example of making do without a Blech is with regards to an oven. Due to a dispute whether – and how – a Blech can be created in an oven, the issue is most easily circumvented simply by ensuring that the food is fully cooked or baked before Shabbos. (In this example, Sephardim may rely on this leniency only when additional cooking will not enhance the food.)

Now, let us apply this to sous vide. Via this method, most foods are generally fully and evenly cooked within a few hours, and they are kept submerged for longer only to improve the texture. According to the Mechaber, this would be prohibited in the absence of a Blech, being that additional cooking enhances the food. However, for Ashkenazim, a Blech would not be needed as long as the food was cooked at least halfway before Shabbos. This can be easily achieved by beginning the cooking process several hours before the onset of Shabbos.

 

Shehiya: Fully Raw Food

There is another possible way to circumvent the prohibition of Shehiya – one which would be acceptable according to all opinions, even according to the Mechaber. Chazal allow one to put completely raw meat on an open flame just before the onset of Shabbos. They were not concerned that one might come to stoke the flames, because doing so would not serve any productive purpose – it would not ready the meat in time for the Friday night meal, nor would it be necessary to ready the meat in time for the Shabbos day meal. This leniency is known as “Kidra Chaysa” (literally: rawpot).

In order for this leniency to apply, two criteria must be met. First, the food item must be one that takes a relatively long time to cook properly (such as meat). Second, the food must be put on the fire just before Shabbos, late enough that it will not begin cooking before Shabbos comes in.

Contemporary Poskim note that this leniency seldom applies nowadays because most modern cooking appliances are able to cook in a relatively short amount of time. As a case in point, meat put up to cook right at the onset of Shabbos would usually be fit for consumption by the time the meat course arrives. Nevertheless, sous vide is a contemporary example of a cooking method that would seem to meet the criteria, for if one starts the process right before candle-lighting, it is highly unlikely that the meat will be sufficiently ready in time for the Friday night meal, even on the highest setting. Thus, the need for a Blech can be sidestepped by setting up the sous vide to begin right at the onset of Shabbos.

[Based on this, one might wish to go a step further and argue that the whole concern of Shehiyah should not apply to sous vide –since it needs to be kept at the same constant temperature throughout, there is no reason why one would come to adjust the heat control. However, for a number of reasons, this argument does not stand; the simplest explanation being that one would be tempted to adjust the temperature if he realised that the sous vide was initially set to the wrong temperature.]

 

Hatmanah: General introduction

We have seen that there are several ways to circumvent the prohibition of Shehiyah when cooking sous vide. However, there is another issue which presents a much bigger problem – the Rabbinic prohibition of Hatmanah; insulation. Broadly speaking, there are two types of Hatmanah:

Hatmanah b’dovor sheyno mosif hevel – This translates literally as “insulating in a medium that does not increase the heat”, or what we might refer to as passive insulation. A common example of this is wrapping a hot pot in towels after it has been removed from the source of heat. The towels do not generate any heat, but merely prevent the heat of the pot from escaping.

Hatmanah b’dovor hamosif hevel – This translates literally as “insulating in a medium that increases the heat”, or what we might refer to as active insulation. A classic example of this is enveloping a pot with coals. A more common  example is wrapping a hot pot in towels whilst it is on a Blech. Although the towels do not generate any heat of their own, they are warm on account of the Blech, and this heat is imparted to the pot. Thus, the towels are  not merely preventing the pot’s heat from escaping, but acting as a medium to conduct external heat into it.

It is fairly obvious that sous vide would fall under the latter category of Hatmanah, for the element heats the water which, in turn, transmits the heat to the submerged food. Therefore, we will restrict the ensuing discussion to this type of Hatmanah.

 

Hatmanah b’DovorHamosif Hevel: Criteria

Chazal treat hatmanah b’dovor hamosif hevel even more stringently than Shehiyah. This type of Hatmanah is forbidden even if it is set up before Shabbos, and the prohibition applies irrespective of the food’s state – whether it is completely raw or completely cooked or anything in between; whether further exposure to heat will enhance it or degrade it; whether the food is hot or cold; or whether the food is needed for the night meal or the day meal. Even after the fact, if one realised on Shabbos that he inadvertently insulated a food item in such a manner, he must immediately remove it from the insulation.

Despite these stringencies, it is not always prohibited to surround food with active insulation. Rather, three conditions must be met:

1.   The food, or the pot which the food is in, must be in direct contact with the insulation. If there is any (clear) gap between, the prohibition of Hatmanah does not apply. One simple example of this is an oven. Although the food  is completely surrounded by the oven, it is not regarded as Hatmanah, for there is a clear gap. Another example is a crockpot, in which there is a clear gap between the internal pot and the external crockpot, according to most Poskim. [For this reason, when lining the external crockpot with foil to act as a Blech, it is important to ensure that this clear gap is not blocked up, as doing so would lead to the far more serious concern of Hatmanah.]

2.   The insulation must have been introduced with the intention of enhancing the cooking or retaining the heat. Conversely, it is permissible to surround hot food solely to protect it from becoming dirty, or for any other side purpose.

3.   The insulation must surround the food sufficiently. There are a number of opinions regarding the parameters of this rule. In the actual text of his Shulchan Oruch, as well as in Kuntras Acharon, the Alter Rebbe takes the approach that the food must be completely surrounded on all sides, including on top, and if it is exposed on any side, even only partially, this does not constitute Hatmanah. However, in his subsequent Mahadura Basra, the Alter Rebbe seems to gravitate towards the opinions who maintain that this type of Hatmanah applies even when the top is completely exposed, as long as the bottom and majority of each of the four sides is covered. The most stringent approach is that of the Mechaber, who rules that any sort of partial insulation is prohibited.

It is pretty clear that sous vide meets all of these conditions:

1.   There is direct contact between the water and the bag containing the food. [Practically speaking, there is also no gap between the bag and the food, being that it must be vacuum sealed. However, even if there was some air trapped inside the bag, to the point that it created a clear and noticeable gap, that would be immaterial, being that there is no gap between the “walls of the pot” – the plastic bag – and the water surrounding it.]

2.   The purpose of the insulation – the warm water – is purely to heat and cook the food, and not to serve some ulterior purpose.

3.   The insulation surrounds the submerged bag on all sides.

 

What about Kishke?

Kishke (or kugel) is commonly wrapped in foil or plastic wrap before being placed inside the cholent. If that is allowed, why should sous vide be prohibited?

It must first be noted that some contemporary Poskim (most notably, the Minchas Yitzchok 8:17 and Shevet Halevi 3:47) do prohibit placing completely sealed kishke inside the cholent, because that would constitute hatmanah b’dovor hamosif hevel. Yet, they suggest a simple solution – puncturing the wrap before placing the kishke in the Cholent. Although we saw above that Hatmanah applies even to food that is mostly wrapped, this is only true when the insulation remains distinct from the food. However, by perforating the wrap, the cholent gravy surrounding the wrap will now enter inside, and the kishke becomes one with the rest of cholent. Obviously, puncturing the plastic wrap is not an option for sous vide, and doing so would defeat its whole purpose.

On the other hand, there are a number of Poskim who allow one to place kishke inside the cholent even without perforating the wrap surrounding it. According to them, this would not transgress the prohibition of Hatmanah. However, their reasons for leniency would not apply to sous vide:

1.   Reb Shlomo Zalman Auerbach seems to have vacillated on the kishke issue. In Shemiras Shabbos Kehilchoso (Chapter 42 Footnote 242), he forbids kishke unless the wrap is perforated. However, in the subsequently released “Tikunim uMiluim”, Reb Shlomo Zalman is recorded as having changed his mind. His rationale is that the kishke and the cholent surrounding it should be regarded as “two foods cooking side by side” which “equally require the source of heat beneath”. This explanation obviously cannot be extrapolated to sous vide, where the sole purpose of heating the water is to cook the food placed inside it.

2.  Others allow un-perforated kishke because, to their mind, it does not meet all the conditions of Hatmanah. As we saw above, Hatmanah applies only when the purpose of the wrapping is to aid cooking and enhance flavour. However, wrapping the kishke does not achieve these aims, and is done purely to prevent it from crumbling or dissolving into the cholent. This explanation obviously cannot be extrapolated to sous vide, where the sole purpose of the insulation –the water bath – is to cook and enhance the food placed inside it.

It should be noted that these two lenient approaches are clearly negated by the Alter Rebbe in Kuntras Achron (258:1), but are possibly compatible with his subsequent Mahadura Basra (§259). Therefore, even with regards to kishke and kugel, it would be best to be stringent and perforate the wrap.

One further reason to permit sealed kishke or kugel is offered by the Chazon Ish (OC 37:32), who innovates that only a solid can serve as insulation, and not a liquid. Accordingly, there is no issue with kishke or kugel surrounded by liquid cholent gravy, and neither would there be any issue with sous vide. However, the position of the Chazon Ish is roundly and soundly disputed by virtually all other Poskim, most prominently the Taz (258:1). The Minchas Yitzchok and Shevet Halevi (ibid) rule that one should not rely on the Chazon Ish in this matter. The words of the Alter Rebbe (Kuntras Achron 258:1) also clearly dispute the Chazon Ish on this point, and therefore, his approach cannot serve as a basis for leniency.

 

Conclusion

Sous vide is prohibited on Shabbos, primarily due to the prohibition of Hatmanah. According to many Poskim, this would prohibit the use of sous vide not just for Shabbos food, but also for food that remains submerged over Shabbos for the sake of Motzei Shabbos or Sunday.

With regards to Yom Tov, when cooking is permissible, the prohibitions of Shehiyah and Hatmanah certainly do not apply, and sous vide is thus allowed.

A final point: Some readers may have, in the past, inadvertently set up sous vide for Shabbos, not realizing that it is prohibited to do so. They may be assured that when done completely inadvertently, the Alter Rebbe rules that one may fall back on certain minority opinions (beyond the scope of this article) to allow its consumption, at least in most cases. Still, the Alter Rebbe stresses that it is prohibited to rely on these minority opinions in the first instance, and if one knowingly did so, it is forbidden to consume the food he prepared.