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Checking core temperature during SV?

richard.fine

There's a lot of useful guidelines now for how long a given kind of substance will take to reach a given temperature - here, in MC@H, etc - lots of 'steak that is 1" thick will take X minutes to reach temperature Y' etc.

But suppose I'm looking to SV something and I don't have such guidelines. What do I do?

If I weren't doing SV, I'd just use a probe thermometer and measure the temperature at intervals until it's getting to the right place. But if I use a probe thermometer with vacuum-packed food, I'm necessarily going to have to break the seal on the bag somehow when I push the probe into the food. So I can't return it to the water bath afterwards, the bag will leak...?

All I can think of is to do a trial run ahead of time with multiple bags of food, and to pull the bags out of the bath at sensible intervals, measure the core temp, and note it down. With any luck I'll get readings on either side of the target (e.g. at 1h the food was 5C below target, at 2h the food was 3C above target, etc) so then I can binary-search to figure out the right time. But this approach seems like it would take an incredibly long time, especially for the larger multi-day things, and also stands to be pretty wasteful...

Or is it just that you do a test run with a single bag of food, but just puncture the bag and don't care about the leakage, the heat transfer properties would be the same? I can see that working for solid things but I guess it could still be a problem for liquids.

Or maybe you puncture the bag with a probe and then re-seal/re-vacuum the puncture hole somehow?

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Comments

seijoed

Use foam tape, get it at Home Depot and you can happily put a probe in the bag.

Polyscience has it on their website so you can see what it looks like.

You can double bag with a ziplock as well to keep it even safer.

richard.fine

Ahh I see - one of those more flexible thermocouple type things? I forgot about those, I was thinking Thermapen-style

So would you put the probe into the bag prior to vacuum sealing - run the wire out the side of the bag, with a bit of foam tape to cover it up?

seijoed

Here is a picture of it -

The thermometer is from the store, the Sper.

Brendan_Lee_56950

Yup silicone tape, similar to what is used to weather proof window sills and the lot will work. What I do is put a small piece on the outside of the bag, then press the probe through. Try and make sure the plastic is flush before you put down the tape to avoid wrinkles and try and use a swift motion to avoid wiggling.

Keep in mind this is only feasible if you have a thermocouple probe attached to a reader since you aren't going to be able to probe it multiple times.

richard.fine

Oh I see! You put the probe through the tape itself, and the tape seals the gap just from the way it works. I thought it was more like electrical tape or something.

seijoed

No, I think it is called foam / insulation tape, it'll keep it leak free.

http://www.cuisinetechnology.com/sousvide.php

There you see a thermocouple and the tape, it works just fine with double-side sticky foam tape from Home Depot.

Either of the two thermocouple thermometers here in the store would work well.

Brendan_Lee_56950

Try and find silicone if you can though to be safe. Cheap stuff may not be good with the long cook times.

seijoed

To answer the original question - are you looking to cook several different types of proteins in say a 60C bath and

pull when reaching core? If so you are probably better off looking at the course material for cook, chill, hold and so on.

I really only use the probes when using smokers / bbq / or cooking seafood from frozen - since that is trickier.

If you cook a steak that is 3cm from frozen - add 30m - 1h to the cooking time, if the bath is set at 54, the meat

will not go above that - period, that is one of the beautiful things with sous vide.

richard.fine

I don't really have any specific thing in mind that I'm asking this question for - I was just looking for the general principle.

Sure, if I'm cooking something that other people have done before (or is covered in the course) then it's not too hard to find a page somewhere, or the course or otherwise, that describes what kind of times I should use. But I've never been one to sit content with just following someone else's recipe ;-)

Knowing how the cooking times are figured out in the first place just gives me a little more adaptability. Makes it easier to handle different sizes of joints and stuff, and makes it more possible to cook weird stuff, like... well, I don't know. Um. Wood chips? Jellyfish? Cheese? Quit putting me on the spot, inspiration will strike when it so pleases

seijoed

Okay

I want to see the thermocouple jelly fish now

Tim_Sutherland_52834

The PolyScience Sous Vide Toolbox App gives you some of the info you are after for various meat proteins. You set the size of the protein and the core temp you want and it gives you the time to cook. Unfortunately there are no choices for Cnidaria or any other gelatinous zooplankton.