Building a sous vide temperature controller

As I’ve noted before (here), I am intrigued with sous vide cooking at the moment.  But, to do it properly you need a precision water bath, and they are pretty expensive (like over £1000) … more than I can justify on playing by about an order of magnitude.  However, it is also possible to use something like a slow cooker, but with a much more precise temperature controller … and you can buy units to do exactly this – for example, from Auber instruments you can get a precision controller for just over $200 shipped (here).  The right answer for me would simply be to buy one of these, but I was interested in just how simple this could be, since you can buy precision temperature control modules for about £25 (look for PID temperature controller on ebay), and the solid state relay to control the power is only about £12.

As projects go, this is close to the level of lego bricks.  The only bit that took any time was cutting holes in the case.  In the photo the temperature sensor is a thermocouple, but I’ve replaced this with a platinum sensor that offers more precision (tenths of a degree, not just degrees … and I didn’t need a range going up over 2000 centigrade!).  I used a 40 amp solid state relay which is massively over-rated, but I thought I might one day want to control an oven, and this would allow it.  It needed no calibration, with a check in a ice water bath reading between -0.1 and 0.1 degrees Centigrade.

As a first long time period cooking trial, I thought I’d go for a rack of lamb. First step is to seal the bags :-

As a water bath I am using a slow cooker. I first ran it without any food in to auto-tune the temperature controller. This allows it to measure the response of the controlled device, and so hold the temperature much more closely than it would otherwise do. Then I put the lamb in, with a heavy metal clip to ensure that if any gas did form then it didn’t leave the bags above water (reminder – this is long cooking at low temperatures, so you need to take special care to avoid issues with bacteria) :-

Then, lid on and a 24 hour wait whilst the controller holds the water at 56 centigrade. It is holding in a band between 55.8 and 56.2 from periodic checks, though photo shows it at 55.6 as it heated the lamb up :-

At lunchtime the next day, I removed the lamb, and browned it. It did plan to use a gas torch, but as a good example that I need to clean the garage, couldn’t actually find it … so, I did it in a pan instead, which is a little tricky for something as awkwardly shaped as a rack of lamb. The end result was superb, albeit probably a little rarer than we might go for next time. It tasted absolutely excellent, even without any sauce. It was also very clear how little shrinkage there was – as the cooking temperature was much lower, the muscle fibres hadn’t contracted nearly as much.

All in all a very pleasing test, and soooo much easier than the first trial that held the temperature by hand adjustment.  I also realise that I can use this for a few other temperature control applications like precision deep fat frying and plant incubation.

e-bay selling – what took me so long?

It has taken us many years to try listing something on e-bay … but I am trying to work out why it took me so long.  I sorted out the camera cupboard last weekend, and though that I might as well try and sell a teleconvertor that I bought for £70 … and at the last minute our 12+ year old film camera.  We got £51 for the teleconvertor and £56 (!!!!!!) for the camera.  Even allowing for the 10% ebay take that feels like a great return for hardly any work.  And, to think we were thinking of putting that camera in the bin as ‘bound to be worthless’.  Why did it take us this long to try this out?

Dappy; How stupid would you have to be

I don’t normally have any more contact with celebrity news than I can manage (sadly that doesn’t mean none).  But the story (see here and here) about Dappy from N-Dubz sending threatening texts to someone who texted radio 1 is almost surreal in its silliness.  In summary, he copied down the number of someone texting to the radio studio, then rang and sent threatening text messages including death threats.  All because they sent in a message saying he was vile and was a little boy with a silly hat (and he does have a very silly hat).

At what point did Dappy (aka Dino Contostavlos which somehow doesn’t sound quite so cool) think that writing down the number of someone texting a radio show was a smart plan?  For Radio One it is a breach of data protection law (this cannot be the purpose for which the information was being stored!)… not sure what law Dappy broke, but it was certainly stupid

How was sending threatening text messages ever going to turn out well for him?  Even assuming he was justified he would immediately be a hostage to fortune.  Especially as someone whose band is an ambassador of beatbullying.

And, I have to say that every time I see N-Dubz I despair about how they can be seen as good enough to be playing in a pub, much less in stadiums.  I’m with Ms. Moody … though I wouldn’t go as far as vile.  I’d just have him flagged as a short person, who wears stupid hats that still fail to distract from a lack of good looks.  And, if he has any skill, he hides it well.

As an aside, Wikipedia might have its flaws, but I love how up to date it is (see here).  Britannica wouldn’t have had an article on Dappy, and it certainly wouldn’t include news an hour earlier than the BBC news feed!

First sous vide experiment

I was reading about Sous Vide cooking over the Christmas holiday.  Sous vide is French for ‘under vacuum’, and refers to a cooking technique of cooking food in vacuum packaging, in a waterbath.  Basically like ‘boil- in-the-bag’, but rather than boiling, it uses very precise control at lower temperatures to get precise changes in various elements of the food.  It’s apparently an outstanding way of doing meat and fish, and it did rather whet my appetite.

I did quite a bit of reading up on it, though there is very little information about since its not really been a widespread technique outside high-end restaurants.  There is a classic thread on egullet  (a forum for professional/high end amateur chefs) here that runs to about a thousand posts spread over more than a hundred pages.  It includes timings for steaks (based on achieving a given core temperature rather than any other change process like converting collagen to gelatin) – it’s many many pages in, so if you want to find it fast, a quick link is here.   There is another thread on precision waterbaths here – certainly something that is needed (see below).

I bought a vacuum sealer which arrived on Friday.  So, even though I have not sorted out a stable waterbath yet, I thought I’d have a go with some cheap (aka disposable!) steaks.  First stage was to seal the steaks in the bags that they would be cooked in.  This was an absolute doddle, and I am quite taken with the vacuum sealer for stuff in the freezer now – it took moments, and can stop freezer burn.  So, at this stage the steaks looked like this :-

The next step was to cook them in a waterbath at a temperature of between 57 and 59 degrees Centigrade for just under 7 minutes (the time required for a 10mm think steak to reach 54.4 degrees core temperature that equates to a medium rare steak).  One advantage of this technique is that with cooking temperatures so close to the desired temperature, the timing can go over by quite a bit without spoiling the food … but without having a thermostatic waterbath, the effort to maintain an exact temperature is pretty high, so I pretty much kept to the target time, using a meat thermometer to check the temperature :-

After the waterbath you have a pretty much perfect steak … but the outside is the same rather unappealing colour as the core, with no browning at all.  So, a moment in a very hot pan to brown the outsides is a fairly common next step (it really is a moment – less than 10 seconds each side worked for us – the whole steak is already pretty hot).  The picture below shows the result – the outside is just browned, with a pretty much prefect medium rare core, and still very juicy, but with no blood.  And, it tasted pretty good as well, though with such a short cooking process, there was no getting away from the fact that it was a cheap ‘trial’ steak!

So, feels worth the next stage of creating a precision waterbath, though I have no huge desire to pay the £500-£1000+ to buy a normal one, so I might try and hack one up (£25 PID controllers from ebay feel made for the job!).  As an aside if you want to see some serious cooking equiment, try www.cuisinetechnology.com/ – I am quite taken with a rotary vacuum evaporator!

A final note – if you do want to play with this, do watch the food safety issues – low temperature cooking can be hazardous, and using vacuum bags can allow the growth of anaerobic bacteria like botulism that don’t smell like aerobic ones, so give you few hints!

Sledging in Wollaton Park

Well, travel may be hazardous, but the sledging is excellent.  Kat and her friends were at Wollaton park today, along with many many others.

Photos here – includes loads of Kat and friends for those who are in my Flickr friends and family groups.  There was a huge variety of sledges, from plastic through classical bend wood frame, to all manner of home-brews. For many, the goal seemed to be to see how many riders you could get on one sledge – loved the three folks below, on one small and surprisingly strong sledge.

There were of course loads of spills, though remarkably, that the injury rate appeared to be pretty low. Good example below of what happens if you try and slide down on a kiddies see-saw.

And, folks of all ages, including one who looked about one.

Not a terribly productive afternoon, but good fun.