Let's be clear, this is not an extensive guide and draws on the knowledge and opinions I have built up researching the subject, prior to purchasing my first roaster and being involved in some commercial roasting activities. I am sure it won’t cover all the home roasters on the market, but will, I hope cover those few machines I have some information/knowledge about and are worthy of consideration. I wanted to pull this guide together (rightly or wrongly) because I did not feel there was enough information in one place for the enthusiast considering home roasting (or indeed coffee roasting). I also don’t want to overcomplicate the issue.
A roaster is a simple device, it heats up coffee until it goes brown and then progressively darker until eventually it can catch fire. The trick to get a good result, is in how the roaster does this, but essentially you need to apply the right amount of heat energy evenly.
First categorise the roasting you will be doing, in this article I only cover the first area, Home Use.
Here you have a number of choices around £400-£600+. There are cheaper roasters but these tend to roast very small amounts 70-80g and a little noisy. I suppose the cheaper ones are a way of testing the water before spending significantly more money, but because it’s harder to get a good result they may put you off.
At the moment (in my opinion) you are really limited to the Gene Cafe and the Hottop. Both of these seem to form the only realistic options for a home roaster. The Hottop is the more expensive of the two, but neither is designed for commercial use. Unfortunately for both these roasters there was only 1 UK importer, a situation which is not usually good for the consumer. Recently however there is a new importer of the Gene Cafe roaster, this makes 2 importers for that particular roaster in the UK, a much better situation for the consumer (especially considering the subsequent price reductions of this unit). The Hottop still has only a single importer and as such you should make your own judgment as to whether this is good for you "the consumer" or not.
The Gene Café
Testing and tasting has shown this roaster to give a superior roast to the Hottop (non programmable version), it is also far more controllable and seems less sensitive to ambient temperature, or voltage fluctuations. It is approximately £80 cheaper than the hottop at the time of writing and requires no regular filter purchases (a further saving of around £80 per year based on a Hottops 4 filters+postage each year). In the Gene it's also easier to back to back roast. I often do 2 or 3 roasts one after the other in the Gene, certainly when testing, it had no trouble doing or more back to back roasts each day for quite a few Kg of coffee, in fact during a single week I probably did around 6 months of roasting!
The accepted "knowledge" on the internet states this is the best home roaster available and a home roaster that gets lots of praise and accolades, by owners and non-owners alike. This certainly has not been the experience of a little testing and tasting amongst 5 or more people, some of whome have sold their Hottops and bought Gene Cafe roasters. The Hottop non programmable model, can take too long to roast (especially in cold weather, or where low mains voltage is a problem) and to bring roast times to an acceptable level, so the beans are not "baked", requires very small batch sizes, often as low as 150g. In winter the roaster is"challenged" and for some people roasting outside in these low ambient temperatures is impossible. Roasts from the hottop generally showed a convergence of flavours to blandness, with a loss of origin characteristics.
Both roasters have to strike a balance in their power output with design considerations, if the heating elements were more powerful I think the structure of the roaster would be affected. If they had to build a structure able to take more heat energy…presumably it would cost more and be much heavier, it would certainly limit the use of certain materials in the roaster structure (increasing size, weight and cost). That said there have been some doubts expressed around the control system of the Hottop making best use of the available power. This seems to be borne out when reading of the improved roasting performance of the new programmable Hottop, where the heating element and the airflow through the roaster can be controlled in a number of roasting "segments". The new programmable Hottop was about £640 at the time of writing….whether this offers £380 worth of "better" performance than the Gene Cafe is unknown, but doubtful. One very important point is the "cleanliness" of the roast, I can't know for sure, but the airflow in the hottop is far less than the Gene and the chaff is collected in a shallow tray below the drum (but still within the roasting chamber area), this could well "braise" the beans in their own smoke (roasting smoke and smoke from smouldering chaff), which would not be good for flavour, although they might smell more pungent after roasting. Interestingly in the new programmable Hottop, I think they have a deeper chaff tray (possibly to reduce this effect)?
Both these roasters have not been around very long, perhaps a few years or more and it is difficult to know how long they will last. Looking at the construction, one could hazard a guess that they will have a reasonably good life for the price (possibly around 5 years or more, depending on usage). Certainly I have recently read and heard of a few heating elements failing on the Genecafe (but I understand they are easy to replace). Also further information seems to indicate that it is very important to have a Gene Cafe roaster of the correct voltage for your country!
Which is the best roaster, is a more difficult question. The majority of people who have tried both, and tasted the roast from both, seem to agree the Gene is at least as good if not better. It's also considered to be better value for money as it's cheaper. In the Hottop the view of the beans is not as good as the Gene and this would make it more difficult to get a roast the colour you want, when between 1st and 2nd crack.
Please remember that roasting produces smoke, this smoke is not always pleasant and in fact it usually isn’t pleasant towards the end of the roast, especially as it becomes more intense and oily or tarry. If you’re going to roast in the Kitchen, you need good extraction, possibly it’s better to roast outside or in the Garage if you can.
Some cautionary notes as well for the home (any) roaster:
1. Put the roaster on an RCD
2. If the roaster is gas, definitely flue it properly and I would even go so far as to suggest you get a carbon monoxide detector (cost around £15) and place it in a suitable location in the room you roasting in
3. Make sure you have a suitable fire extinguisher
4. Have a heatproof pair of gloves to hand (and I mean heat proof!). You might need to handle a very hot object and move it or do something to it in a hurry.
5. If you roast (on any type of roaster) at night or in the dark, it is ABSOLUTELY ESSENTIAL to do it next to a rechargeable light source that will come on automatically should the power fail. This leaves you both hands free to make the roaster safe. Some beans/roasters roasters very near to the end of the roast could catch fire if the power fails, because the airflow stops, but the element is still hot. If I am wrong about this it’s cost you a few pounds, if I am right, it could save your life. Personally I use a rechargeable emergency light (dual 18W fluorescent tubes) wall mounted (it's also removable), right next to the business end of my roaster. If the power fails on this will switch on automatically and give 36W of light for an hour or more. Being fluorescent the light is equivalent to that given by a 100 watt light bulb. Mine was purchased from Halfords for a very reasonable £15
6. Try and ensure someone knows where you are and what you’re doing!