Gene Cafe Coffee Roaster Review
by Randy Glass - Copyright 2007 - All rights reserved

Gene Cafe Coffee Roaster

      The Gene Cafe coffee roaster has been available for about two years now and I finally have the opportunity to review this appliance. From the first time I saw its unique design and roasting mechanism, this roaster has intrigued me.
      Maybe the most unique thing about this roaster is the manufacturer! Genesis is the manufacturer of office furniture systems in South Korea (these office systems are available in the US). I could find nothing on their website to tie the two things together other than the have their own R+D team as well as their own manufacturing systems to develop their furniture lines from start to finish.
      The roaster uses forced hot air which passes through the drum from right to left (facing the front of the machine). Its unique property is that bean agitation is not supplied by the air but rather by the rotation of the drum, The drum is mounted off-axis so the drum appears to 'tumble' as it rotates. The geometry of the drum's mount and the careful design of the separating panel inside the drum which creates two, interconnected halves of the chamber combine to create a stirring of the roasting beans that is not only unique but also very effective.


      Lets start with the drum. The drum is inserted by holding it at an acute angle to the machine which places the extensions on the ends of the drum parallel to the driving plates of the roaster's base. It is a bit confusing at first to those of us who live in a perpendicular world, but if you watch the drum's right end and insert it first, sliding it down into place flat against the driver plate, the left end pretty much takes care of itself.
      The drum itself is made of Pyrex, borosilicate glass and seem quite thick and robust, so with care it should last a good long time.

      Sliding the drum all the way down causes a latch on the left side (mounted to the top of the drum) to engage, holding the drum in place. There is no safety switch and so the machine can be operated without the drum in place.

      The Gene Cafe comes with a stand for the drum allowing it to stand upright on a counter. A very handy inclusion since the drum's ends are not parallel and if the drum it stood up without the stand it has the potential of being easily knocked over.

      Filling the drum with beans is a simple matter of flipping open the top which is held in place by friction. Pour in the desired amount of beans using the included, 100-gram capacity scoop (or weigh them if you have a scale) and close the lid.

      The instructions specifically state that the separator (divider) inside the drum is not to be removed. I was later informed by a Gene Cafe representative that it is OK to carefully remove the separator, but great care should be taken so as not to be injured by the sharp edges, particularly on the chaff cutter. As you see here I was still able to slide mine out without difficulty. It makes cleaning the drum an easy matter.

      One of the many ingenious features of the Gene Cafe is the chaff cutter. Mounted at the end of the separator, this weighted flap flops back and forth on its hinge rings as the drum turns. It has a scraping end which moves across the drum's slotted exhaust port. Its job is to keep the exhaust slots clear of chaff and other debris which might restrict the flow of hot air. In actual use it seems to be virtually 100% effective in its task. It has little rubbery bumpers to cushion it's drop against the glass drum, and two extra bumpers come with the machine. I would have preferred having the plastic molding of the drum's end extended to protect the glass so that the scraper could never reach the glass surface, thus eliminating the need for the bumpers. On the other hand, if they last long enough, they effectively quiet the flopping of the chaff cutter. Against the quiet operation of the machine the sound of the flopping chaff cutter, even with the rubber bumpers, will make you think that there is something wrong with the machine the first time you use it.

      The chaff collector looks rather large for a roaster with a capacity of about 300 grams. It is easy to put into place by simply sliding its neck into the exhaust opening at the left end of the machine. There is no safety switch to be sure that it is in place before roasting, and very hot air and chaff will issue forth from the machine during roasting if it is left off. Because of the low exhaust port this does have the potential of damaging counter tops or possibly creating a fire hazard, so be sure the chaff collector is in place before starting. The collector's large size has little resistance to the flow of air and it also easy to clean. It can be washed in hot water, but the manual states that no parts of the Gene Cafe are dishwasher safe.

      To clean the chaff collector simply remove the end cap and dump the chaff after the roaster has cooled. The outer surface of the collector becomes quite hot, so care must be taken before removing the collector. The stainless screen outside is matched by one inside.

      The controls of the Gene Cafe are quite simple. The two knobs shown here control all functions of the machine.
- Press the right control in and it operates as a momentary switch for power on and power off.
- Turn the right switch as you would a volume control and it sets the roasting time up or down from 0 to an amazing THIRTY minutes! That's a long time to roast coffee! Beyond that, you are able to continually raise the time to 30:00 over and over during the roast, so a seemingly unlimited amount of time can be used to roast.
- Press the left switch and it starts the roast or begins the cooling process (stops the roasting cycle).
- Turn the left switch and it adjusts roasting temperature up or down from 140 degrees to 482 F.

      The time and temperature settings can be adjusted at any time, either before the roast begins or during the roasting process.

      As unique as the outside of the machine appears, the real show is inside! Yes, my business card should say:
"Have screwdriver - will disassemble. I do it so you don't have to."

      The machine is quite easy to open with no hidden screws nor tabs to worry about breaking. With the drum off the machine just remove the screws on the bottom of the machine. All the screws are in holes with a tapered bottom so when you replace the screws they slide right into place, even in the deeply recessed holes. Turn the machine right-side up, remove the two screws holding the heat reflector under the drum and lift off the reflector. There are two plastic parts that seal the ends of the heat reflector, one at each end of the shield. Lift these off and the entire top of the machine lifts right off. Now just remove the two connectors at the end of the ribbon cables which connect the control panel to the machine and that's it.

      Inside the machine you find a study in industrial design. The placement of the parts, the way the wires have been run, the simplicity of design, and the design of the individual parts are all done in a way that reflects a very high level of engineering and design skill. Let's take a look at the major parts:

      This is the business end of the machine. This heavy, cast aluminum chamber contains the heating element. Mounted on top is a thermocouple which senses the temperature of the air just before it enters the roasting chamber. The two halves of the chamber are screwed together and sealed with clear RTV sealant.

      Here is the blower motor which forces cold air through the heating chamber. It's intake is on the bottom of the machine making it important to place the machine on a smooth, clean surface. There is a filter screen built into the bottom of the machine that the manual states should be brushed clean occasionally to maintain proper air flow.

      This is the driving plate at the heating element's end (right side) of the machine. You can see the exit of the heating chamber in the center. Notice that the heating element's casting continues right into the opening. At the bottom-right of the picture you can see the gear and shaft that drives the drum on the right side.

      Both of the drum driving plates are supported by two small bearings. These take most of the weight of the chamber and beans. This is important because...

      ...the motor that drives the drum appears quite small, but the drum is so well balanced and the gear reduction at both ends so efficient that all this motor has to do is turn the drum which takes little torque. In use there is no lurching or hesitation of the drum; its smooth motion reflects excellent design.

      Here is the exhaust end of the machine. You can see the thermal sensor in the port which I believe is used, among other functions, to display the temperature on the control panel.

      The roasting process is quite simple.

1 - Slide the chaff collector into place
2 - Pour the coffee beans into the drum
3 - Close the chamber's lid and snap the drum into place on the roaster
4 - Plug in the machine to the appropriate outlet.
5 - Press "Power" and the display illuminates.
6 - Spin the controls to set the desired amount of time and temperature.
7 - Press "START" and the roast begins.

      When the programmed amount of time expires the roaster enters the cooling cycle. Of course, you can end the roast at any time you wish by pressing the "COOL" button and the cooling cycle starts.
      The rudimentary programming doesn't allow the creating or saving any curves or profiles. When the time reaches "0" the roaster enters cooling mode. The temperature seems to be just a general level stetting and I saw no information in the manual as to specifically what this does to the roasting profile if adjusted during the roast. It does give a chart as to the temperature to use along with times to achieve the "standard" roast levels. For example, set the Gene Cafe to 19 minutes and 482 degrees for a Full City roast. it does thoughtfully mention that factors such as what beans are used as well as line voltage will affect these.
      Speaking of the manual, you will notice that it was apparently written or translated by someone who knows English as a second language. You will find sentences here and there will take more then one reading to completely understand. Some of the warning messages on the stickers on the machine read in the same way.

      One of the more difficult things to do is document roasts with the Gene Cafe. There is no easy way for me to record bean temperature since the roaster is essentially sealed at both ends of the drums. Even if I had modified the chaff collector end of the drum to pass a thermocouple through I would still have had to deal with the chaff cutter and the divider panel in the drum. The rolling nature of the drum and the shifting of the beans would complicate matters even further. The tumbling nature of the beans means that regardless of where I placed the sensor, at some point during the roast it would not be in the bean mass.
      Additionally, the heating element seems to be cycled in a binary manner and the air temperature in the drum fluctuates so that recording the temperature at the exhaust port only gives a general idea of the programmed curve. This also makes any manual adjustment of the roast temperature during the roasting process a bit of a guessing game.
      My brain keep wanting something like of a set of thermocouples in the drum which rest in the bean mass, selected using a gravity switch (the one in the beans at any given time is the one connected). It could connect to the machine using contacts that engaged when the drum is snapped into place. Unfortunately, something like this would add some serious complications and would increase the cost of the machine.
      I began with a test roast of some sweep just to see how the thing works. Although the cracks are audible, they are muffled by the design of the Gene Cafe, so placing an ear near (but not over!) the exhaust of the chaff collector will help you hear what is going on.
      I took the beans in this first roast to right around the point that I normally would for most coffee- just into active second crack by about ten seconds or so. I stopped the roast by beginning the cooling cycle. That was a mistake as I quickly discovered this machine's greatest weakness- its cooling cycle. It is virtually non-existent.
      The cooling cycle turns off the heating element and increases the air flow of the fan. All this accomplishes for the first few minutes is to continue to roast the coffee. It took about 8:30 of cooling time before the display showed that the beans dropped below 200 degrees. My thermocouple in the exhaust port of the left end of the drum indicated that after eight full minutes of cooling that the air exiting the chamber was still at 200 degrees.
      The standard cooling cycle ends when the temperature reaches 140 degrees. For this roast it took fifteen minutes. I poured out the beans and measured their temperature, and even after exposing them to the air and stirring them a bit with a stainless thermocouple probe in a colander they measured around 120 degrees. The beans ended up so dark and oily that I threw them into the trash.
      Facing the disappointment of such a long cooling cycle I fabricated a simple bean cooler. I found a dishwashing detergent bucket that my colander fit into nicely, and I cut a hole in the bottom of the bucket to accept the hose from my shop vac.
      The manual gives the user a few alternatives to allowing the beans to cool in the machine. For serious home roasters these methods are critical for ending roasts at specific levels. Of course, you can press left, "START/STOP" button at any time to enter the cooling mode to end a roast, but that leaves the beans in the rotating drum. The better method is to get he beans out of there and cool them externally. To do that, press and hold the "START/STOP" button for about two seconds. the display will show "E StP" [Emergency Stop] and the drum will park itself with the handle up, but the fan will continue to blow air in order to cool the heating element.
      My next roast was 275 grams of Brazilian. At the end of the roast I stopped the drum as outlined above, put on a leather glove and I grabbed the handle, released the latch and pulled the drum out of the roaster. I opened the chamber's lid, poured the beans into the cooler I had built, and started the shop vac. I replaced the drum in order to cool the unit more effectively. With a slight amount of stirring, in less than thirty seconds the beans could be comfortably held in the hand, and in well under one minute the beans were cool to the touch.
      Maintnance chores are a simple matter. It is most important to maintain the air flow through the drum This means cleaning the air intake screen on the bottom of the roaster with a brush as well as cleaning both the inside and outside screens of the chaff collector. If oils build up on the chaff collector, mild detergent and a brush can be used to scrub it clean. Wash the drum out ocasionally and be sure that the chaff screen at the chaff cutter is clear of bean particles, That is about all that is needed to keep the roaster working at its best. There are no filters to replace.
      As you can see from the internal layout of the Gene Cafe, all parts are easy to access and so replacement, if needed, should be an easy matter.
      It is nearly impossible to offer any detailed, in-depth roasting curve data because of the design of the machine (no access to the beans during the roast) and its method of heat control (the binary nature of the heat delivery). Even if those relative figures are accepted it makes it difficult to compare the roasting curve to other roasters. So for what it is worth, here is a graph I made from that first test roast:

      The red line represents the digital display readout on the Gene Cafe's control panel. The purple line is from data I hand collected using a thermocouple wire in the chaff collector up in the exhaust port. You can see that they are roughly parallel. Discounting the movement of the thermocouple during the roast and the effect that chaff collecting on it may have had, as well as other factors, it is safe to assume that the roaster's display is showing the temperature as sensed by its own thermocouple in the exhaust port.
      I allowed the Brazilian roast to rest for 24 hours then used them as a single-origin espresso. I think most would agree that if you were to do a single origin espresso, Brazilian beans would not necessarily be number one on the list. I normally use them as a base bean for my espresso blends because of their simple, smooth taste. With that in mind, this batch was quite tasty. Smooth and buttery mouth-feel with a natural sweetness. Nothing to get excited about but quite drinkable. Enough so that it might start some experimenting in single origin espresso which I have never done.
      For this next roast I once again measured out about 275 grams of the same Brazilian beans. My goal was to test the Gene Cafe's ability to control the temperature through the use of the manual temperature control. The roast was as follows:

300 F. 0:00 to 4:00
375 F. 4:00 to 8:00
431 F. 8:00 - 11:00
465 F. 11:00 to 14:00
482 F. 14:00 to 15:00
      The various temperature change inputs from the control panel are color coded and labeled above in the graph. The temperature changes were not done to emulate any specific roast or to achieve any taste results but to document just how well (or not) the machine would respond. Data was gathered once per minute during the roast. As you can see, the machine has an excellent ability to modify its temperature with a fast and predictable reaction time, and it was able to achieve and hold a set temperature with virtually no overshoot. The temperature began to rise virtually the instant I changed the set temperature using the knob on the control panel.
      More importantly, take note that I was able to easily bring a 275 gram batch of beans to active second crack in fifteen minutes without pushing the roaster (or the roast) at all!
      After about four days' use there is little to not like about the Gene Cafe. Even though the Gene Cafe website states, "You can enjoy the best flavor & taste of coffee through the quick cooling," the serious user will have to create some sort of external cooling device, even if it is as simple as using a metal pot or colander kept in a freezer until needed into which the beans can be poured. The forced air system I built for bean cooling is basically a copy of the cooling tray on all commercial machines and is very effective, with the added benefit of further cleaning the beans of stray chaff. Fortunately, the designers of the Gene Cafe included a way to easily stop the drum and park it in a place to make it easy to remove so that it can be removed at any time the user chooses. If you plan on doing this, heat-resistant gloves are a MUST!
      The lack of bean temperature monitoring is likely more of a problem for me than for most other folks. I am accustomed to being able to see the bean temperature from using other roasters which I have equipped with thermocouples, so if the Gene Cafe is your first roaster with a temperature readout you will be able to learn to judge roast level and bean temperature from the display and from listening to the cracks. After just three roasts I already have a pretty good feel for how it works.
      Finally, the lack of any memory or way to save a roast profile means that the user will need to closely attend every roast and manually make changes throughout the roasting process, and do so for every roast.
      Other than that, this machine is nice to look at and easy to use, and it appears to have a rock-solid, simple design. The level of control over the roast is just about all you could ask for. Fit and finish is exquisite and the design supplies as even of a roast as a home roaster could expect. Works good- looks good- makes good coffee.

     ADDENDUM- 8/17/2007 - I tried to roast a 305 gram batch of coffee. I found that this was beyond the Gene Cafe's ability to roast properly. As the beans expand near the end of the roast, their increased volume restricts their movoment in the drum and apparently also restricts the air flow. This cause a very uneven roast— the most uneven roast I have ever esperienced. Most of the beans roasted properly but there were quite a few which were very dark and oily. I do not know what the exact maximum capacity is with the Gene Cafe, but for best results I would recommend keeping your maximum roast to around 275 grams.