Though I use these small 100 to 250 gram roasters at home or to quickly sample some green beans I do not find them practical in a commercial setting. In a cafe a micro roaster with a 33 lb/hr capacity is more practical, gives more consistent results and has cheaper operating costs per pound of roasted beans. The nano roaster will roast a small batch of green beans cheaply, show you the advantage of freshness, and will encourage exploring various roast levels. In this Blog I prefer to focus on Cafe On-Site Roasting with the 33 lb/hr (15 kg) Micro Roasters. These will be examined under various titles in other posts. This post looks at an inexpensive introduction to coffee roasting.
The tiny roasters are often the realm of the adventurous who are doing this at home or because they wish to explore a new freshness dimension for their product line. Of the "at home group" usually only the truly passionate for Freshly Roasted Coffee will continue to roast after the novelty wears off. At first impression the nano roaster is an inexpensive roasting introduction especially if a buyer ignores that they are light duty machines. A small roaster requires as much supervision as a micro 33 lb/hour machine. Therefore the greatest cost becomes the labour per lb roasted. Let's say that gathering the information is important and that lower margins, at this time, are secondary.
Many small roasters are designed more for selling than great roasting. That nice glass container gives the buyer comfort but no one puts a "Clean me Regularly - when cold" sticker on it. Windex works quite well but I would at least do a finishing wipe with alcohol unless you really like the Windex flavour (I have not used Windex inside the Roasting Chamber but thought there should be a caveat). I have yet to see a home-style coffee roaster with pollution controls. They just get away with it because of their small batch size. It is not "green" roasting and it actually wastes most of the energy because the air is heated then ejected. Some people have the romantic idea that there will be a coffee aroma wafting through the room. Wrong! Think more in the line of many simultaneous burning toasts, hence the vented fume hood. Roasting outside is often problematic because of the temperature differential required to reach the roasting temperature. On colder days the small electrical heating element may not have the capacity to sufficiently raise the temperature of the air entering the Roasting Chamber. It is possible to increase the heat by slightly closing some of the louvers. Don't overdo it or you reduce the capacity of the roaster or even worse melt the fan or burn the motor. All this means the roasting strategy should incorporate a fallback option or a forgive me clause, "I was wrong" so that you can try again.
In choosing any roaster I would say that heating/cooling the beans evenly is most important. There are ways to do that but it is a real challenge to do that with a normal household electrical circuit. I prefer the air to do the mixing because it will also push the air through the beans to heat more evenly. If the beans are shooting up like a fountain the air is not evenly heating the beans. So called automated Roast Controls should be only counted on to give a rough guide. Coffee Roasting is a chemical reaction that has many inputs. When the beans' requirements are fulfilled the reaction will start. The problem, of most if not all nano roaster controls are unable to integrate the variables or inputs that affect the roast. Voltage fluctuations affect the heating element and the fan therefore it is not an ideal time to roast when power consumption is high i.e. meal times. Green coffee beans are living seeds that absorb humidity which must be evaporated at the beginning of the roast. Humid conditions presents a double whammy because the beans have a higher moisture level and the humid air is less able to carry it away. Ambient temperature affects the capacity of the element to heat the air. Too low and the beans will be baked. Higher altitude and low barometric pressure will also reduce the heating and mixing efficiency but it also lowers the boiling point of the moisture. If the roaster is hot from previous batches less time will be required. In an analysis of a database of thousands of roasts we found that the start of pyrolysis (the chemical change caused by heat starting at a bean temperature of 190 to 205°C according to different sources - the phase where sugars are caramelized ) can vary over 1.5 minutes for the same bean and degree of roast.
The first thing is to develop a plan based on advice from existing roasters. I have reservations about calling the sales pitches - useful advice. Potential difficulties are related to capturing chaff, diverting the smoke, and cooling exothermic beans (yes they get that hot).
Before posting this there was a little trip through blogland to see what was written. The worst suggestion is the frying pan method because there is only a point of contact between a surface curved on two axes and a flat surface which means the bean is overheated on the point of contact and under heated elsewhere. The street vendors in London have figured this out so they roast chestnuts in hot sand for more even roasting. Popcorn poppers do not cause condensation on the beans - the temperature is well above boiling point. Don't spray water to cool the beans and to make up for the weight loss during roasting. Remove some beans from the popcorn popper if the batch is not mixing at the beginning because the bottom layer will quickly scorch. Have a look at a previous post "Not Sustainable Roasting" for anecdotal evidence that companies don't always understand this process. If there are unclear statements or questions just leave a Comment.
Better roasting was achieved with the no longer in production Popcorn Pumper because the Mabuchi motor drives the fan blade at a higher speed. We no longer find these in stores but they are found "used good outlets" such as Goodwill, St. Vincent de Paul, Value Village etc. The Popcorn Pumpers sell for $2 to $7 and often little used. Generally I buy them for the motors because the solid bronze bearings do wear too quickly. It is possible to remove and install the Impellers but push the Shaft out and support the Shaft at the back of the Mabuchi when pushing the Impeller on. The 24 VAC transformer has lasted 25 years but there has been at least 15 motor changes because when the bearings are worn the speed decreases which lowers the capacity it can handle.
In reconsideration, this may be overwhelming, it is easier to just do it, after planning the cooling process.
