ChefSteps' Joule: Food meets tech. Result? Delicious!

chef mod
Credit: The Blue Diamond Gallery

The Joule immersion circulator from ChefSteps cooks up sous vide with a big helping of technology for a great price


When I’m not writing about technology or playing wi-, er, testing software or hardware, I cook. Food and cooking are two of my passions and one of the worst things about being in the tech world is that cooking usually has to take second place. Today, however, I have the pleasure of combining tech with my culinary pursuits as I recently got my hands on a really cool cooking device that’s Bluetooth and Wi-Fi enabled and controlled by a smartphone app. The device is an immersion circulator called Joule that was developed by one of my favorite foodie resources, ChefSteps

joule app steak ChefSteps

Joule in water bath, companion app, and a steak. And a knife. And a person.

I have to digress at this point to encourage you to check out ChefSteps’ beautifully designed Web site and, in particular, to watch their Wall of Fire video which I've included below for your amusement; the combination of whole pigs and insane amounts of heat yet again proves why food, fire, and danger is a winning formula. Also check out The Ultimate Guide to Making Crispy, Amber-Hued Peking Duck at Home (note that you’ll need an air compressor; yep, really).

So, if you’re a techie who subsists on Twinkies and soda from the company vending machine you might, at this point, be wondering what on earth an immersion circulator is, what it’s got to do with cooking, and why I’m so excited about the topic.  To explain that we have to explain a cooking technique called “sous vide.”

Sous vide? isn’t that French for …

The term “sous vide” is French for “under vacuum.” The process involves sealing the food to be cooked in a bag, removing the air from the bag, then placing the bag in a temperature-controlled water bath. Note that vacuum packing can be dispensed with; you can put the food in a Ziplock freezer bag and submerge the bag in water so that the water pressure collapses the bag and forces the air out.

The temperature-controlled water bath which is where the immersion circulator comes in, it’s the thing that keeps the water bath at a precise temperature. The goal of sous vide cooking is to take the food to the exact temperature needed for a specific time (we’ll come back to how long later) to achieve a very specific level of “doneness.” 

For example, using the sous vide technique, if you want to cook a one-inch thick steak to medium rare you’d season it with salt and pepper, vacuum pack it, set the water bath to 130 °F, and take it out after 45 minutes. If you cut into that steak, what you’ll find will be perfectly cooked meat that’s medium rare from edge to edge. You can optionally give the steak a quick sear in butter or oil, in a pan or on a barbecue, to develop a “crust” and or grill marks; the former for extra flavor due to the Maillard reaction while the later is mostly for aesthetic purposes. Here’s what a seared sous vide steak looks like compared to a traditionally cooked steak …

steak comparison ChefSteps

Comparison of a medium rare steak cooked sous vide and conventionally

Note that the traditionally cooked steak on the right has  a gray zone that extends from the surface to about a quarter of the way to the center. What this means is that the steak is medium to medium well-done (or even completely well-done) on the outside and medium rare in the center. Compare that to the sous vide steak on the left which is medium rare throughout except for a very thin crust created by the sear. 

The result of using sous vide is very different from what you get with conventional cooking techniques. Consider barbecuing, sauteing, or roasting: If you're cooking meat whatever method you're using will be in the zone from around 375 to 450 °F. This is an external blast of heat and particularly on a barbecue, unless you’re careful, by the time your steak reaches 130 °F in the center, the exterior could well be a charred ruin more suitable as a burnt offering to the gods.

Why sous vide is so damn good

But wait! There’s more! The mouth feel of anything cooked sous vide can be noticeably different from conventional cooking because you can cook food for a short time at a high temperature or a long time at a low temperature and the longer the time, the more tender the food will become (at least it does up to a point after which it will most likely turn to mush). So, for a tough cut like beef short ribs, you can sous vide them for 12 hours at 185 °F for a conventional slow braise tenderness, or for 72 hours at 129 °F for a tenderness that will blow your mind (ChefSteps has a great post on the results of sous vide cooking beef short ribs for various time and temperature combinations). 

tenderloin donenesses 5 ChefSteps

Sous vide beef tenderloin cooked to specific "doneness"

What’s even more amazing about cooking sous vide is that when your food has reached the target temperature and time, you have a huge window in which you can “hold” it at it's serving temperature. For example, if you're cooking steak, when it's done you have about a two hour holding window! This is fantastic if your guests are late or you’re not so good at cooking multiple dishes at the same  time. 

I could go on at great length about the wonders of sous vide cooking (such as technical stuff like how you know how long to cook so that bacteria are killed off and the incredible things you can do with sous vide eggs or how to cook the best turkey breast you've ever eaten) but let’s get back to immersion circulators …

So, what is an immersion circulator?

Immersion circulators are actually sophisticated devices that keep the temperature of sous vide water baths constant using a proportional–integral–derivative controller (PID controller) which is a type of control loop feedback system.


pid block diagram

PID block diagram

Wikipedia explains:

A PID controller continuously calculates an error value as the difference between a desired setpoint and a measured process variable. The controller attempts to minimize the error over time by adjustment of a control variable, such as the position of a control valve, a damper, or the power supplied to a heating element, to a new value determined by a weighted sum:

pid math

The mathematics of a PID controller

In the case of the ChefSteps Joule, the temperature control accuracy is 0.2 °F  with a maximum temperature of 208 °F and a maximum bath volume of around 10 gallons. This is impressive as the Joule costs $299 ($205 if you pre-order) while a professional immersion circulator (a PolyScience MX) I purchased in 2012 is priced these days at $800 (the RRP is $1,000). The PolyScience is rated at the same wattage (1,100W) with a greater accuracy (± 0.126 °F - note that this increased accuracy doesn’t, in reality, make a huge difference), a higher maximum temperature of 275 °F, but is rated for a maximum bath volume of only 7.3 gallons.

joule tech specs.0 ChefSteps

Joule construction

A Design Jobs would have appreciated

The Joule's design is elegant; a simple cylinder with a magnetic foot to hold it in place as well as a clip for non-metallic baths. The water is sucked up from around the foot by an impeller, heated, then ejected through the slot on the side. There's a switch and an indicator light on the top and that's it. It's a design that would have pleased Steve Jobs although he would have no doubt put a great big Apple logo on it.

So far, this is all well and good but, you might be wondering, is that all the tech that’s involved? No, my friend, there’s more: The Joule uses Bluetooth LE, Wi-Fi, and routing over the Internet to connect to a smartphone app that allows you to start and stop heating as well as set and monitor the bath temperature from anywhere you can get IP dial tone. You could be on the other side of the world and still keep an eye on what your Joule is doing.

The apps, which are nicely engineered and provide a huge amount of sous vide advice and recipes, are available for iOS 8.0 or later and Android 4.4 or later. These apps are currently optimized for smaller screens “so your viewing experience will be superior on a smartphone.” 

joule ios app Mark Gibbs

Joule's iOS app (from left to right: app startup, setting target temperature, monitoring progress with a timer running)

Setting up and pairing with the Joule with the apps is very simple, even complete tech newbies will find it easy. Something I really like is that once the setup is completed, the Joule communicates with the app over Wi-Fi so you’re not tied to staying within a 30 foot range. I’d like to see a desktop app as well as the iOS and Android apps (I had a quick look to see if the Joule has any open ports to play with but no luck … I’d love to write my own control application).

Let's test the Joule!

My test was beef short ribs cooked at 135 °F for 24 hours (I’ve usually done them for longer but that time and temperature combination was recommended in an article on another blog). The Joule worked perfectly and in operation it’s very quiet and unobtrusive. 

joule in bath ChefSteps

Joule in a water bath (this is not my kitchen)

I used a beta version of the iOS software and found a couple of minor bugs but I just got a new a new release via TestFlight so I think more serious testing is in order (the 72 hour beef short ribs sounds just the ticket). The one thing I noted was that the app needs a disconnect alarm … if something goes wrong or the power to the Joule gets cut, the app should shriek as loudly as possible; you don’t want to wake up in the morning to find that your sous vide dish has been sitting slowly cooling for the last eight hours instead of cooking.

So, how good is the Joule?

So, bottom line: The Joule is outstanding. It’s beautifully designed, the price is great and I have every reason to believe that the final software will be excellent. The Joule gets a Gearhead rating of 6 out of 5.

Yep, you read that right. I know, I know, that a first for Gearhead. How can that be a 6? ‘Cause I said so. He who cooks, calls the tune. Now I’m off to do more testing. Maybe I'll skip the short ribs and do a recipe I’ve done a couple of times before; ChefSteps’ Homemade Honey-Glazed Ham. Total crowd pleaser. Bon appetite!

Comments? Thoughts? Email me your recipes or post 'em below then follow me on Twitter and Facebook.


chefsteps glazedham 9 ChefSteps

ChefSteps glazed ham (mmmmmmmmm)


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