If your idea of a six-course meal is a small order of chicken nuggets, you might have missed the rise of sous vide among cooks. The idea is you seal food in a plastic pouch and then cook it in a water bath that is held at a precise temperature. That temperature is much lower than you usually use, so the cook times are long, but the result is food that is evenly cooked and does not lose much moisture during the cooking process. Of course, controlling a temperature is a perfect job for a microcontroller and [Kasperkors] has made his own setup using an Arduino for control. The post is in Danish, but Google translate is frighteningly good.
The attractive setup uses an Arduino Mega, a display, a waterproof temperature probe, and some odds and ends. The translation does fall down a little on the parts list, but if you substitute “ground” for “earth” and “soil” you should be safe. For the true epicurean, form is as important as function, and [Kasperkors’] acrylic box with LEDs within is certainly eye-catching. You can see a video of the device, below.
The switches, LEDs, and relays are all pretty standard fare. The real heart of the project is the temperature control. Many controllers use a PID (proportional/integral/derivative) to hold the temperature, but this project takes a more pragmatic approach. Depending on how far from the set point the temperature is, the controller simply drives the heating element differently and measures more or less frequently to adjust. For example, if the temperature is more than two degrees low, the heating element is left on constantly. As it gets closer, though, the heating element runs for 10 seconds, there’s a 5 second wait, and then the algorithm reads the temperature again.
There’s a lot of debate about how precise the temperature has to be. Apparently, for things like fish, a wide range of temperatures isn’t a problem. Eggs, however, need tighter control because their proteins can denature (whatever that means).
There’s also a safety relay that shuts the whole affair down if the temperature goes very high or low so a bad temperature sensor won’t boil everything away. We might have considered doing that with a bimetallic coil so that even an Arduino failure would not stop it from working.
We’ve seen other attractive sous vide setups. Not to mention the more utilitarian builds made with a crock pot. No matter what it looks like, these projects are probably not going to help your waistline.
Interesting mix of working machine yet and the time spent to fabricate an enclosure yet still using a breadboard. Unclear why a PID wasn’t used exactly? They are so cheap these days.
What kind of risks are there with sous vide? You are kind of making a petri dish that sort of very slowly cooks things. Maybe it’s more akin to a slow cooker in that it is sterile enough to kill pathogens?
Anyway, you can’t be bothered to look up what denaturing is?
Wikipedia has an interesting definition but that doesn’t really specifically apply to egg protein in a digestible way.
“Denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), radiation or heat.”
Here is a bit of a better explanation:
http://www.livescience.com/28575-science-of-cooking-perfect-egg.html
“When an egg is cooked, the proteins in the yolk unravel, a process known as denaturation. Proteins can be denatured by strong chemicals such as acids, mechanical action or heat — as in the case of the 6X-degree egg.
There’s a false notion, even among scientists, that proteins have definitive, discrete denaturation temperatures, Vega said. “The belief is, 67 degrees C [153 F] is the temperature at which egg yolk proteins start to coagulate,” he said, but that isn’t true. It all depends on the thermal history of the egg, he explained: “I can heat it at 35 degrees C [95 F], and if I wait long enough, it will denature it.” Boiling the egg denatures it too, but it happens so fast that the textural outcome is different, Vega said.
Some proteins in the egg yolk denature at higher temperatures than others, Vega found, and more proteins denature the longer the egg is cooked. The hotter the temperature and the longer the cook time, the more viscous the yolk becomes.”
Depending on how much water you want to heat up the controlled system changed and you have to tune your PID controller for every mass you want to heat. With a hysteresis controller like this you don’t have to tune it and i think the control accuracy is even better then with an bad tuned PID controller.
Allegedly, USDA danger zone numbers have an amount of drool-proofing built into them, and >135degF will actually kill bacteria, albeit slowly.
http://www.divediscover.whoi.edu/hottopics/bacteria.html
“Bacteria at hydrothermal vents inhabit almost everything: rocks, the seafloor, even the inside of animals like mussels. All are living under extreme pressure and temperature changes. Perhaps the oddest and toughest bacteria at vents are the heat-loving ‘thermophiles.’ Temperatures well above 662°F (350°C) are not uncommon at vents. The “world record”; for life growing at high temperatures is 235°F (113°C), a record held by a type of thermophile known as a hyperthermophile. These themophiles grow best above 176°F (80°C).”
Sous Vide doesn’t have to kill any kind of bacteria on earth. It needs to kill the bacteria that can make you sick. This link has all you heed to know to cook food safely, as well as the math behind it.
http://www.douglasbaldwin.com/sous-vide.html
Exactly. The USDA’s standards wouldn’t even bother a thermophile.
ROTFL!
The next time I’m using sous vide to cook a steak from a cow that hung around undersea thermal vents, I’ll keep this in mind.
I think it’s a young person thing. Saying “whatever that means” is code for “I think it’s stupid that people make up things that I don’t understand so I will mock them with my passive aggression.” It ends up making the author look stupid, but only to people old enough to understand what’s going on.
Funny. I met Al at a Houston meet up this week. He’s at least 40 or 50. I don’t know what’s funnier. That people don’t get a little sarcasm, or that people feel like anyone gives a crap about how you reacted to an offhand bit of humor. The fact is the post isn’t about the physics (chemistry?) of sous vide cooking. But even so. People say stuff on the Internet and radio and TV that I don’t like all the time. I just don’t get riled up about it. I don’t know. I guess I’m not unhappy or insecure or whatever it is that drives people to be so critical of every damn thing.
Try reading this: https://tinyurl.com/7xdqx48
Might make you enjoy the Internet a little more.
Good article Al.Good to meet you this week.
Two quotes:
“What kind of risks are there with sous vide? You are kind of making a petri dish that sort of very slowly cooks things. Maybe it’s more akin to a slow cooker in that it is sterile enough to kill pathogens?”
“Anyway, you can’t be bothered to look up what XXXX is?”
I’m sorry, guess I’m just too much an analog engineer. This can be done much easier with an LM10, an LM34 and a solid state relay. Schematic is on the LM34 data sheet. (LM35 sensor for those needing Celsius settings, but schematic on 34 data sheet.) Add in a DPM for setting and reading and the project will still run under $20.
A simple analogue solution wouldn’t be able to deal with the higher order parameters, leading to massive overshoot as residual heat dissipates from the element into the water, ruining the food. You also really ought to be using a proper food safe temperature probe, too.
Really? Gosh an analog controller worked just fine on a primary standards lab resistor oil bath. Maintained temp within a few tenths of a degree. The cooking liquid itself ought to supply all the hysteresis needed to deal with residual heater temp swing. As to a food safe probe: TO92 in heatshrink ought to be just fine. Not happy with that make a press fit teflon sleeve.
Since the whole point is that the food is sealed in plastic, what’s the point of ä food safe probe?
Mchael
I gotta try this form of cooking even if some of the tools (http://www.seriouseats.com/2016/01/first-thing-to-cook-with-sous-vide-immersion-circulator-essential-recipes.html) are as expensive as a pressure cooker.
Just plug a crock pot (set on high) into a good temp controller. See LM34 data sheet for the schematic I mentioned.
Does the food has to be vacuum sealed in the bag or it is ok if some air is present inside the bag while cooking?
I don’t think so. Probably just get air out of bag do it will fully submerge.
So.. not do…. Doh I hate touch keyboards!
No the food will be fine wirh some air. I think the die is to have the water in contact with all sides so the food heats evenly. Ive made a crock pot sous vide and the steaks and other stuff came out just fine.
I think they typically put them in Ziplocs for howebrew solutions, then either extract the air with a straw (yuck?) or submerge it with the lock open slightly. And I think you sometimes still get a floater, but I’m only going by videos and articles I’ve seen.
Floaters can also happen when you cook at higher temps where gas is released from the food during the cooking process. You can always let the air out of the Ziploc in the middle of the cook or weigh down the bag ahead of time. Some people put marbles inside the bag. I use a few butter knives either outside or inside, depending on the size of the bag.
Marbles + food = choking hazard and possibly a chipped tooth.
Butter knives + food = perforated intestines.
The main point of vacuum sealing I think is to prevent bag blow outs while cooking. I don’t know if you have tried making bag eggs, but if you have too much air in the bag when you dunk it in the hot water the bag can rupture. I imagine that reducing floating is also a factor.
Get a cheap $5 DC high temp pump and recirculate the water. Food will cook faster and more evenly. There will be gradiation in that hot water bath.
Heating element will also melt thin poly bags. I would suggest a screen or protective barrier around the heating element.
Also, minimal air in the bag is desired so the hot water can make contact with all surfaces of the food. To use a ziploc, put your food in, then submerge the food with the bag open and the opening above the water line. The pressure from the water will force out enough air, then seal it while food is still submerged.