Sous Vide – Tevilat Keilim and Warming Food on Shabbat
Two questions regarding a sous vide:
1) Does it require tevilah?
2) Can it be used to reheat food on Shabbat, assuming it is on and in heated water from Erev Shabbat?
1. It does not require tevilah. It does not come in direct contact with the food (plastic bag and water both intervene). (Shulchan Arukh YD 120:4, Arukh HaShulchan YD 120:32, Sefer Tevilat Keilim, 1:4 ft. 7)
2. If we are talking about something that is yavesh u’mevushal kol tzorcho (dry solid, and fully cooked), the issue would be netina li’chatchilah (Shulchan Arukh OC 253:4, Mishnah Berurah 253:89). To me, this would definitely be a problem. This seems like it is definitely derekh bishul (standard way of cooking) (Shulchan Arukh OC 253:4, Mishnah Berurah 318:59). Why should it be any better than putting something directly on a fire or in the oven?
It is possible that the Sous Vide could be an issue of hatmanah, a problem from before Shabbat, or even if it is off, as the food is being surrounded by hot water from all sides, and could this be considered hatmanah be’davar ha’mosif hevel (insulating food with something that preserves or increases heat). (SA OH 257:1). Rav Asher Weiss discusses the issue and comes down la’chumra (strictly).
My initial instinct is that when it is keeping the food that was cooked in it inside the hot water from before Shabbat is not an issue of hatmanah. Here, the food is in the liquid it was cooked in. It should be no different than keeping kreplach in the pot with hot water it was boiled in – even if the water itself won’t be eaten. That’s when it’s the object that was cooked in it and is being kept in it from before Shabbat. As to putting some other food in it before Shabbat to warm it up or preserve the heat, or putting the same food back on Shabbat, it might well be more derekh hatmanah.
To clarify – the general rule is that there is no hatmanah of food in food. If I submerge my chicken in hot rice, that is not hatamanah. Here, however, one could argue that the plastic bag is like a pot. And if I submerge a chicken in a pot into a mound of hot rice, that is hatmanah. (MB 278:2) One could additionally argue that the water here is not ochel (food) since it is only made for cooking, not eating. I do not find that persuasive. My example of hot water and kreplach is the same. If I submerged a cold chicken into that water that was still hot, that is not hatmanah. But if I submerged it in a pot in that water, that is a problem.
So – the solution here to all the above is to use it without the plastic bag. If you do this, it is not derekh bishul, so not problem of netinah li’chatchilah (even if it is on), and it is ochel betoch ochel (food in food – see above), so no problem of hatmanah. Even if one were to argue that it is still ochel betoch ochel when it is in the plastic bag, and no hatmanah problem, it still remains a netinah li’chatchilah problem if it is on.
Now one might ask – what if you use a different pot? Would that work as a shinui (non-conventional usage)? First, shinui isn’t the issue, it is whether it is mechzi k’mevashel (appears like cooking – see for example MB 253:55, MB 253:86). So it really comes down to the question – would someone seeing you do this think you are cooking with a sous vide and just using a different pot, or would they know you are only reheating something? (We do netinah li’chatchilah to a hot plate, because (almost) no one cooks on a hot plate (Yabia Omer OH 6:32 ,Igrot Moshe, OH 4:74:35). Whether we can do netinah to a blech on a fire – where cooking is possible, yet just odd – is heavily debated, and most Ashkenazim, as far as I know, do not do it unless it is kadeirah al gabei kadeirah or the like. Meaning – weird isn’t enough, it really has to be not so realistic to cook on this).
Also to add -in addition to mechzi k’mevashel, there is also a concern of shemah yechateh (one might come to adjust the temperature). I think a strong argument can be made that that is not a problem in the case of a sous vide, since one never adjusts the temperature once set. Anyway, some tape over the buttons would certainly suffice for this concern.