DIY Sous-vide controller

[Jethro_uk]

Was lucky enough to snaffle a food vacuum sealing unit from Lidl (£24.99) last week ... It's already impressed the Jethro household (for vacuum sealing before freezing and preventing drying out).

I notice with interest another possible use for vacuum sealing is to prepare sous-vide meals. Well, the vacuum sealing bit anyway.

Casual googling seems to suggest that the most important part of sous-vide is a *constant* temperature. Meaning the swings of a slow cooker won't do.

There are some "turn your slow cooker into a sous vide cooker" gadgets. But (a) they are priced in dollars, which suggests a long delivery time (if at all), and (b) a tad pricey at that.

Really, all that is needed is a thermocouple and a dial-in temperature controller which switch a mains feed on/off.

Annoyingly I have one of these around :

I wonder if there's a way to either remove and extend it's thermocouple, or connect an external one in (which would need calibrating, I guess).

*Or* is there a better way I've not encompassed ?

"Proper" sous-vide cookers are in the hundreds, but I can't help but feel that's probably because that's what John Lewis can sell them for.

[Bob Eager]

My chef son seems to think this is OK, at least for his experiments.

There is rather a lot of Chinglish!

[Jethro_uk]

Thanks, will dig a bit.

[Huge]

Rather a lot of money, too.

[Peter Parry]

Ambiano Sous Vide Wand Aldi, £ 49.99

[Jethro_uk]

Now that looks interesting ...

[Theo]

Certainly Sir:

about a tenner including all the bits.

I stuck one in a box with the appropriate mains connections and a thermocouple socket - it's very handy for lots of things where you have a crude heating element and want to control it better. The instructions don't necessarily match the software on the one you get, but I've not done more than setting the set point - that works fine, I checked with an IR camera. (it certainly isn't a genuine RKC unit, so don't expect support)

I tend to use bare thermocouples as they have less thermal mass than the screw type:

I suspect that's thermistor sensored, range something like -20 to +50C - no good for a cooking appliance.

The PID units are extra cheap from China because they have a lot of industrial control needs in their factories and they fit on the standard control panels.

Theo

[Jethro_uk]

Thanks, that's very interesting.

[Thomas Prufer]

Yes, there is a cheaper way, at least for your beef and fish (those are in the

49 °C -- 60 °C range, for times of an hour or three.

I use a large, thick styrofoam box with a well-sealing lid, previously used for shipping sensitive supplies in dry ice. Bung in lots of too-hot water, say 10 liters, add cold carefully to desired temp, reading the temperature with an accurate thermometer. Bung in sealed bag, put lid on, wait. Also known as "beer cooler sous vide"... though cold beer is an USAnian thing, you get the idea.

Alternatively, fish can go in the dishwasher on the 50°C cycle.

Thomas Prufer

[Peter Parry]

Sous Vide involves tight control of temperature (+ - 0.5 deg) and often times of 24 to 48 hours.

Douglas Baldwin writes some of the best science based books on the subject.

[Theo]

Should have said, those were just random ebay listings - I have no recommendation of particular sellers.

Big Clive has a video on the SSR:

Theo

[Andy Burns]

I had never heard of sous-vide, wikipedia told me that Heston uses it which was all I needed to know ...

[newshound]

Wouldn't know about its internals, is it a thermocouple or a thermistor? A lot of thermistor based controllers are only good to 50 degC.

Like you, I was seduced by a Lidl sealer a few months ago. I happened to have a number of small industrial temperature controllers hanging around, I think the one I used in the end was a 0-100 or 0-200 C with an iron-constantan thermocouple (readily available from eBay).

I use this to control a water bath in an ordinary slow cooker, but with the thermocouple in the water and I reckon this controls OK to a fraction of a degree. I get the temperature controlling before I put the food in, this of course drops the temperature but brings it up to the control point with negligible overshoot.

Works very well for good steaks (finish with a pan sear of course).

Plenty of 50mm DIN panel fitting controllers around for a tenner or so if you don't mind waiting for shipping from China

[newshound]

That's a pretty sensible price. I think I would add some insulation to the pan, though.

[newshound]

Silly me, should have read all the posts before responding!

[newshound]

I'm a bit skeptical about whether those extended times really make a difference. But I do tend to do the "bagging up" the day before, with plenty of herbs/spices etc. I'll usually leave beef or lamb out of the fridge overnight after bagging too.

[Thomas Prufer]

Yes... I have a "laboratory thermostat" I use for sous vide when i have longer cooking times. (A laboratory thermostat is a machine that keeps water at a constant temperature: heater/temperature probe/ circulator pump, sometimes cooling, all in a box.) I've also compared thermometers, and found that the variance can be +- 1 K among kitchen thermometers of reasonable quality, and cheap ones can be so far off that guessing temperatures is better.

Fish has sous vide times that max out at 60 minutes for thick fillets, say 41°C for half an hour for very rare salmon. Or beef (T-bone) at 49-53 °C for one to two hours.

These are times and temperatures that a 2" styrofoam box with 10-20 liters of water will maintain easily with sufficient accuracy. I've done it, where I had no mains electricity, but a source of hot water (and a charcoal grill to sear meat with).

Thomas Prufer

[Tjoepstil]

yes, that plus a 'blood temparature 'of 40C and a cooking time of many hours should ensure the best chance of lethal bacterial colonies developing...

[Caecilius]

And an *accurate* temperature as well.

You'd be better off with a PID controller that can modulate the heater than an on/off switch connected to a simple temperature controller.

[spuorgelgoog]

Hay-box cookery was demonstrated on the (repeated) Going Back In Time for D inner when fuel was short during WWI.

The wood they used to make their hay-box probably costs more than the Aldi thing.

Owain