Cooking Salmon in a Sous Vide

Question

A Sous Vide cooker is a sophisticated immersion coil with a small circulation fan. This device clamps onto a pot and heats up water so that food can be cooked at exact temperatures while circulating the water in a way that the heat is distributed equally throughout the pot.

The Gemara (Shabbos 40b) says that water and oil are cooked at the temperature of yad soledes. The Sous Vide presents fascinating questions concerning this halacha. Because of its sophisticated cooking mechanism, the Sous Vide can cook salmon and certain other foods at a temperature under yad soledes bo.

If I cook my salmon on Erev Shabbos at the temperature the recipe calls for, which is 42.5° Celsius (108.5° Fahrenheit), which is under yad soledes according to many poskim, can I then reheat it on Shabbos if the fish will get to a temperature that is above yad soledes?

A second question: When cooking with a Sous Vide device, the food is placed in a sealed zip lock bag in order to preserve its natural moisture and only then immersed in water. After the fish is prepared with a Sous Vide, do we consider the food to be boiled, since it was cooked with water and is wet from its natural moisture which collected in the zip lock bag? Alternatively, do we consider the fish to be roasted, since the water did not actually touch the fish, or is it considered tzli keder, like pot roast?

The reason I am concerned whether the salmon prepared in the Sous Vide has the halachic status of being cooked and whether we classify this process as boiling or roasting is because if I reheat the fish on Shabbos, it can get dried out and crispy. If the preparation is considered boiling, then maybe warming it up on Shabbos presents a problem of roasting after boiling.

Thank you.

Yishai Lipschutz

Monsey, NY

Rav Auerbach 

You have asked a number of excellent questions that are not clear-cut issues in the poskim. Let us deal with each one separately:

Cooking Under Yad Soledes

The Gemara (Shabbos 40b) rules that water and oil require a temperature of yad soledes to become cooked. Although the Gemara does not explicitly discuss the temperature needed to cook solids, the poskim seem to assume that there is no difference (see Shabbos 42a-b regarding tavlin and Mishnah Berurah 318:45). Nonetheless, I believe that there are a number of reasons why food cooked at a temperature of under yad soledes in a Sous Vide may be considered halachically cooked.

There are some foods that become cooked with less heat than others. Thus, even though many foods are only cooked when heated up using direct fire, some foods do not require this. For example, the Gemara (Shabbos 39a) writes that certain types of fish are cooked when pouring hot water over them from a kli sheini (see Tosafos ibid.).

Kalei Habishul

Some Rishonim write that "the effect of cooking depends on the substance that is being cooked and not on whether it is prepared in a kli rishon or kli sheini" (Mordechai 302, Yerei’im 274). Based on this understanding, if the fish is heated up in a Sous Vide and after this preparation the food is considered cooked, we can assume that bishul may have taken place even under yad soledes.

Even if most foods would not be cooked at a temperature that is under yad soledes, it may be that salmon can be considered kalei habishul. Although most poskim imply that even kalei habishul require a temperature of yad soledes to be cooked, some write that certain foods can be cooked under yad soledes (Aishel Avrohom 318:37).

Even though the other poskim only apply the halacha of kalei habishul to cooking in a kli sheini which is yad soledes, they may agree that using the sophisticated mechanism of this cooking apparatus creates a situation where even under yad soledes can cook.

Cooking or Roasting

As far as your second question of whether the effect of the Sous Vide is defined as boiling or roasting, I believe that since the fish is cooked with heat that travels through water, this is considered boiling and not roasting. The water does not have to actually touch the food to be classified as boiling, but rather, as long as the food did not get heated by direct heat of a fire but by heat that traveled through water, it is considered boiled.

We can bring a proof to this from the halachos of hagalas keilim. If someone heats food on top of a water urn and then wants to kasher the urn, the urn needs hagalah afterwards and not libun. This shows that if heat travels through water, it is defined as bishul and not tzli.

The Bottom Line

1. If salmon was cooked before Shabbos at under yad soledes using a Sous Vide, it should not be reheated on Shabbos.

2. Although there are arguments that cooking in the Sous Vide under yad soledes may be halachic bishul, since there is a possibility that the fish may not be considered cooked before Shabbos, reheating might be bishul.

3. Even if the fish was fully cooked in a Sous Vide before Shabbos, if reheating the fish makes it crispy as if it had been roasted, this may be considered tzli after bishul.

4. If salmon was cooked before Shabbos at a temperature above yad soledes using a Sous Vide, one may reheat it on Shabbos on an upside-down tray on the platter or blech, as long as doing so does not produce a roasted effect on the taste of the fish, and is therefore not considered tzli after bishul.