There’s a lot of mysticism around coffee roasting, but in the end it couldn’t be simpler. Take a bunch of beans, heat them up evenly, and stop before they get burned. The rest is details.
And the same goes for coffee roasters. The most primitive roasting technique involves stirring the beans in a pan or wok to keep them from scorching on the bottom. This works great, but it doesn’t scale. Industrial drum roasters heat a rotating drum with ridges on the inside like a cement mixer to keep the beans in constant motion while they pass over a gas fire. Fluidized-bed roasters use a strong stream of heated air to whirl the beans around while roasting them evenly. But the bottom line is that a coffee roaster needs to agitate the beans over a controllable heat source so that they roast as evenly as possible.
My DIY coffee roaster gave up the ghost a few days ago and I immediately ordered the essential replacement part, a hot air popcorn popper, to avert a true crisis: no coffee! While I was rebuilding, I thought I’d take some pictures and share what I know about the subject. So if you’re interested in roasting coffee, making a popcorn popper into a roaster, or even just taking an inside look at a thoroughly value-engineered kitchen machine, read on!
[Avidan Ross] has an unyielding passion for coffee. Brewing a proper espresso is more than measuring fluid ounces, and to that end, his office’s current espresso machine was not making the cut. What’s a maker to do but enlist his skills to brew some high-tech coffee.
For a proper espresso, the mass of the grounds and the brewed output need to be precisely measured. So, the office La Marzocco GS3 has been transformed into a closed-loop espresso machine with a Particle Photon and an Acaia Lunar waterproof scale at its heart.
The secret of cold-brew coffee is out. Department stores are selling gimmicks to make it at home or you can make it with a mason jar in good old-fashioned DIY style. This method is for the on-the-go hacker who may not have even the most spartan of equipment to brew a cold cup of Joe. Many hotel rooms are outfitted with a cheap percolating coffee machine and proprietary pods. The pods are just a sachet of filter paper with ground coffee inside.
Leave that percolating fire hazard unplugged and brew those pods overnight in a glass of water. In eight hours, you have a cup of rocket fuel. Compost the spent pod and away you go. Don’t heat your brew in the coffee maker, that’ll probably wreck it. Nuke it if you need it hot.
Have you ever thought about coffee purity? It’s more something you’d encounter with prescription or elicit drugs, but coffee is actually a rather valuable commodity. If a seller can make the actual grounds go a bit further by stretching the brew with alternative ingredients there becomes an incentive to cheat.
If this sounds like the stuff rumors are made of, that’s because it is! Here in Ho Chi Minh City there are age-old rumors a coffee syndicate that masterfully passes off adulterated product as pure, high-grade coffee. Rumors are one thing, but the local media started picking up on these suspicions and that caught my attention. I decided to look to simple chemistry to see if I could prove or disprove the story.
What we want to investigate is whether price and coffee purity are related. If they are, then after accounting for the effect of price, we will want to know whether proximity to the market where artificial coffee flavoring is sold has an effect on coffee purity.
I take coffee very seriously. It’s probably the most important meal of the day, and apparently the largest overall dietary source of antioxidants in the United States of America. Regardless of whether you believe antioxidants have a health effect (I’m skeptical), that’s interesting!
Unfortunately, industrially roasted and ground coffee is sometimes adulterated with a variety of unwanted ‘other stuff’: corn, soybeans, wheat husks, etc. Across Southeast Asia, there’s a lot of concern over food adulteration and safety in general, as the cost-driven nature of the market pushes a minority of vendors to dishonest business practices. Here in Vietnam, one of the specific rumors is that coffee from street vendors is not actually coffee, but unsafe chemical flavoring agents mixed with corn silk, roasted coconut husks, and soy. Local news reported that 30% of street coffee doesn’t even contain caffeine.
While I’ve heard some pretty fanciful tales told at street side coffee shops, some of them turned out to be based on some grain (bean?) of truth, and local news has certainly featured it often enough. Then again, I’ve been buying coffee at the same friendly street vendors for years, and take some offense at unfounded accusations directed at them.
This sounds like a job for science, but what can we use to quantify the purity of many coffee samples without spending a fortune? As usual, the solution to the problem (pun intended) was already in the room:
They say that if something is worth doing, it’s worth doing right. Those are good words to live by, but here at Hackaday we occasionally like to adhere to a slight variation of that saying: “If it’s worth doing, it’s worth overdoing”. So when we saw the incredible amount of work and careful research [Rob Linnaeus] was doing just to roast coffee beans, we knew he was onto something.
The heart of his coffee roaster is a vortex chamber with an opening on the side for a standard heat gun, and an aperture in the top where an eight cup flour sifter is to be placed. [Rob] modeled the chamber in Fusion 360 and verified its characteristics using RealFlow’s fluid simulation. He then created a negative of the chamber and printed it out on his Monoprice Maker Select 3D printer.
He filled the mold with a 1:1 mix of refractory cement and perlite, and used the back of a reciprocating saw to vibrate the mold as it set so any air bubbles would rise up to the surface. After curing for a day, [Rob] then removed the mold by heating it and peeling it away. Over the next several hours, the cast piece was fired in the oven at increasingly higher temperatures, from 200 °F all the way up to 500 °F. This part is critical, as trapped water could otherwise turn to steam and cause an explosion if the part was immediately subjected to high temperatures. If this sounds a lot like the process for making a small forge, that’s because it basically is. Continue reading “The Fine Art of Heating And Cooling Your Beans”→
[Mike] is the only one in his house who drinks coffee, and uses a simple single-serving brewer with no auto-on feature. And since no one really wants to have to stand around making coffee in the morning, [Mike]’s solution was to IoT-ize his electrical socket.
The project consists of a relay board controlled by an ESP8266-packing Adafruit Huzzah. It’s all powered by a 9V power supply with a regulator supplying the relay coil and Huzzah with 5V. [Mike]’s using CloudMQTT to communicate with the outlet.
We often see these automation projects hit a wall when it comes to adding a user-side dashboard. [Mike] is using a free Android app called MQTT Dash which allows for a number of different UI components and even had coffee maker icons already built in. It’s certainly worth a look for your own projects. [Mike] uses it to turn on the outlet for 10 minutes, and by the time he grabs half-and-half the outlet is already off again.