Fermenter on the desk, with the front door opened and some tempeh disks visible inside of it

Hackaday Prize 2022: An Easy-To-Build Fermenter For Tempeh

[Maud Bausier] and [Antoine Jaunard] believe we should all know about tempeh — a traditional Indonesian food made out of legumes fermented with fungi. To simplify the process a bit: you get some soybeans, add a tempeh starter fungi culture to them, ferment them a while, and out comes the tempeh. It’s a great source of proteins that’s relatively easy to grow on your own. One catch, though — you do need a certain kind of climate to have it develop properly. This is why [Maud] and [Antoine] are bringing a tempeh fermenter design to this year’s Hackaday Prize.

Ready tempeh disks cut into long pieces, showing the cross-section of some. It looks pretty tasty!This fermenter’s controller drives a heating element, which adheres to a pre-programmed fermentation cycle. It also has a fan for airflow and keeping the heat uniform.

The fermenter itself is a small desktop machine with a laser-cut case helped by some CNC-cut and 3D-printed parts, electronics being a simple custom PCB coupling a Pi Pico with widely-available modules. This is clearly a project for someone with access to hackerspace or fab lab resources, but of course, all of the files are on GitHub.

Once built, this design allows you to grow tempeh disks in home conditions on a small scale. It seems the design is mostly finalized, but if you’d like to hear news about this project, they have a blog and a Mastodon feed with some recent updates.

We’ve covered a whole lot of fermentation-related hacks over these years. Most of them have been alcohol-related, but every now and then we see people building fermentation equipment for other food materials, like vinegar, yogurt and sourdough. Now, having seen this fermenter, we’ve learned of one more food hacking direction to explore. This project is one of 10 finalists for our latest Hackaday Prize round, Climate-Resilient Communities. It’s a well-deserved win, and we can’t wait to see where it goes!

Fermenting Yogurt With The Help Of Hardware

Fermentation is a natural process that has been exploited by humanity for millennia. Behind such favorites as cheese and beer, it takes just the right conditions to get the desired results. To aid in this process, and to explore the crafts of their ancestors, [Victoria] and [Petar] created an electronic fermentation quilt.

Bulgarian yogurt was the tasty end result from this work.

Anyone familiar with breadmaking will be familiar with throwing a cloth over dough when left to rest. This is all about temperature management, providing optimum conditions for the yeast to work their magic. This fermentation quilt takes things to the next level, integrating soft heater pads and temperature sensing hardware into the fabric itself. Rather than acting as a simple insulator, the quilt can actively supply heat where needed, switching off when reaching the set temperature. In this example, the quilt is set to maintain a temperature of 45 degrees for the optimum production of Bulgarian yogurt.

The fermentation quilt serves as an excellent example of what can be achieved when combining textiles with smart electronics. Tools like Adafruit’s Lilypad and conductive thread all come together to make this a functional and useful device, and shows that electronic textiles aren’t just limited to blinky wearables.

Fermentation is a popular topic among hackers, with [Trent Fehl]’s Supercon talk at the 2019 Supercon covering similar ground from a sourdough perspective. It goes to show that hardware skills can pay off in the kitchen, too!

Fail Of The Week: Exploding Fermentation

It’s no secret that hackers like fermentation, both the process and the end results. I myself have a crock of sauerkraut happily bubbling away in the kitchen right now. Fermentation can lead to tasty endpoints, and the process itself, which basically amounts to controlled rotting, is a fascinating set of biochemical reactions. But done wrong, fermentation can result in injury, as it did at CCC this year when a fermentation vessel exploded.

"It was the one on the left, officer. He did it."
“It was the one on the left, officer. He did it.”

Exactly what happened isn’t really clear, except that Food Hacking Base ran a number of workshops at CCC 2015, several of which involved fermented foods or drinks. A Grolsch-style bottle with a ceramic flip-top was apparently used as a fermentation vessel, but unfortunately the seal was not broken. The bottle found its way to another tent at CCC, this one running an SMD soldering workshop. Carbon dioxide gas built up enough pressure in the bottle to shatter it and send shrapnel flying through the workshop tent. According to a discussion thread on the incident, “people got hurt and need to go to the hospital because glas [sic] particles were stuck in their faces, a throat was cut and an eyelid bleeding.” The explosion was quite energetic, because, “we also found a 20cm long piece of glass that went trough [sic] the ceiling of the tent and propelled for another 4-5 meters afterwards.”

We’ve seen lots of Hackaday projects involving instrumentation and automation of fermentation, including some with really large vessels. The potential for destruction if such a vessel isn’t properly vented is pretty high. At the very least, you’ll be left with a really big mess to clean up. Be careful out there – microbes are not to be trifled with. We don’t want to give you the wrong idea about CCC; this year was incredible as [Elliot Williams] reported during his time there.

Now it’s off to the kitchen to check on my kraut.

[Thanks to Morgan for the tip.]

Beer Brewer’s Temperature Controller


Steady fermentation temperatures, usually at about 65 degrees Fahrenheit, are an important part of brewing beer. Because of this, the wort (unfermented beer) is often temperature controlled during fermentation. [android] needed a temperature controller for fermenting beer in a chest freezer. Much like the energy efficient fridge hack from last month, the chest freezer is switched on and off to achieve the desired temperature. Instead of buying a controller, [android] built around an existing design. His project uses a solid state relay to switch an outlet on and off.

The temperature is controlled by a home thermostat. He removed the thermistor from the unit and extended it with 24 gauge wire so that it can go inside of the chest freezer. Utilizing a junction box, the freezer is plugged into one switched outlet and controlled by the thermostat via the relay. The other outlet is unswitched and provides DC power for the relay using a wall wort transformer. Although this thermostat cannot be set cold enough for lagering, it is perfect for keeping kegs at the correct beer serving temperatures when not being used for fermentation.