I get the impression (simply from reading posts about coffee roasting, so I might be wrong here) that most roasting machines are meant to work with a specific batch size. For example, a 1kg coffee roaster is meant to work with a 1kg batch, no less, no more.
I can understand the no more, but why no less? What could happen if I use a 100gr batch on a 1kg coffee roaster? Isn't it all temperature controlled?
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I get the impression (simply from reading posts about coffee roasting, so I might be wrong here) that most roasting machines are meant to work with a specific batch size. For example, a 1kg coffee roaster is meant to work with a 1kg batch, no less, no more.
I can understand the no more, but why no less? What could happen if I use a 100gr batch on a 1kg coffee roaster? Isn't it all temperature controlled?
I can understand the no more, but why no less? What could happen if I use a 100gr batch on a 1kg coffee roaster? Isn't it all temperature controlled? Thanks, Ronen
The roast will go very fast indeed and probably be uneven. The fast roast will prematurely force bean oils to the surface....the end result will be something for the bin.
The roast will go very fast indeed and probably be uneven. The fast roast will prematurely force bean oils to the surface....the end result will be something for the bin.
To my plain understanding, it should not matter if the batch is small or large, as long as temperature is controlled and the beans are kept moving. What am I missing here?
I get the impression (simply from reading posts about coffee roasting, so I might be wrong here) that most roasting machines are meant to work with a specific batch size. For example, a 1kg coffee roaster is meant to work with a 1kg batch, no less, no more.
I can understand the no more, but why no less? What could happen if I use a 100gr batch on a 1kg coffee roaster? Isn't it all temperature controlled?
Despite what others have said, you could use a 100g batch in a 1kg roaster, but this brings some difficulties: a) the bean mass is a large component of what maintains temperature stability; more beans = slower temp rise (or fall). A larger roaster is designed to provide more heat faster to a larger mass. You'd have to control the heat more precisely and with some roasters this isn't easy to do. Think of a cycling heater that normally cycles on a thermostat with a 2C hysteresis (or on/off range); with less bean mass this might wind up being 5C or 10C. b) any kind of profile that has been provided by previous experience will be mostly useless as it was based on a much larger batch. c) you effectively waste some significant energy, kind of in the same way that running a Nascar racer in city traffic does. The roaster "engine" is built for a different type of use than roasting tiny batches.
Having said that, you probably won't find much trouble roasting 500g in a 1kg roaster. Unfortunately I don't have any experience with these larger roasters, but I have no problems roasting 150g in my 250g Gene Cafe. You will have to adjust temp and time control, however.
Despite what others have said, you could use a 100g batch in a 1kg roaster, but this brings some difficulties:
Having said that, you probably won't find much trouble roasting 500g in a 1kg roaster. Unfortunately I don't have any experience with these larger roasters, but I have no problems roasting 150g in my 250g Gene Cafe. You will have to adjust temp and time control, however.
I have roasted in a 25kg gas powered Probat and a 1kg Toper Cafemino, in neither roaster could you even contemplate roasting 1/10 of it's capacity e.g. 100g in a 1kg roaster or 2.5kg in a 25kg roaster. In the large 25kg Probat, it was difficult to roast less than 13kg with any small measure of success and even then it was not ideal. Dropping around 30% to 40% of max capacity is possible with these commercial roasters, but you then have to watch them like a hawk and of course be aware that the profile the roaster will try and follow is very different.
So I am afraid I have to disagree with what you say, based on my experience of commercial roasters (1kg and 25kg). It's also why they make 5, 10 15 20kg roasters etc..if they would all roast small batches as well as they roast large batches, you would only need 10 and 20kg roasters, why bother making 5 and 15s....the fuel saving would not be significant, between a 10kg roaster roasting 5kg and a 5kg roaster roasting 5kg
I have roasted in a 25kg gas powered Probat and a 1kg Toper Cafemino, in neither roaster could you even contemplate roasting 1/10 of it's capacity e.g. 100g in a 1kg roaster or 2.5kg in a 25kg roaster. In the large 25kg Probat, it was difficult to roast less than 13kg with any small measure of success and even then it was not ideal. Dropping around 30% to 40% of max capacity is possible with these commercial roasters, but you then have to watch them like a hawk and of course be aware that the profile the roaster will try and follow is very different.
There are plenty of reasons why you would bother making different sizes of roasters. As svyerkgeniiy said, you waste some significant energy when using a small batch in a large roaster. Other than that, not everyone have enough room to accommodate a big roaster. And of course, why not make several models if people actually believe they need two or more roasters .. ?
I have roasted in a 25kg gas powered Probat and a 1kg Toper Cafemino, in neither roaster could you even contemplate roasting 1/10 of it's capacity e.g. 100g in a 1kg roaster or 2.5kg in a 25kg roaster. In the large 25kg Probat, it was difficult to roast less than 13kg with any small measure of success and even then it was not ideal. Dropping around 30% to 40% of max capacity is possible with these commercial roasters, but you then have to watch them like a hawk and of course be aware that the profile the roaster will try and follow is very different.
So I am afraid I have to disagree with what you say, based on my experience of commercial roasters (1kg and 25kg). It's also why they make 5, 10 15 20kg roasters etc..if they would all roast small batches as well as they roast large batches, you would only need 10 and 20kg roasters, why bother making 5 and 15s....the fuel saving would not be significant, between a 10kg roaster roasting 5kg and a 5kg roaster roasting 5kg
I was going under the assumption that, as long as you really really watch it, you could find some success. I imagine it depends on the mechanics and heat control of the roaster, though. For example, your fluid bed roaster probably wouldn't work well if you don't have enough "fluid" to circulate. What is the major difficulty? Circulation? Temp ramps too quickly? Edge of batch roasts faster than the middle? Or is it too hard to tell what the problem is?
The problems are a combination of things you mentioned in your earlier posts and for fluid bed type roasters, I have little experience of them apart from the Gene, which is a bit of a Hybrid. I know that in a Gene insufficient bean mass allows a lot of the heat to simply flow out of the roaster...so sometimes the results are counter intuitive (even though it might heat up faster, or appear to).
In the commercial roasters, it's too complex to pin down on any one thing e.g. with a smaller bean mass the surface of each bean is in contact with the surface of the drum or longer, dependiong on the mix of heating type such as predominantly IR (specific type of IR) or convection conduction, there is yet another effect, possibly on tipping as well.
To my plain understanding, it should not matter if the batch is small or large, as long as temperature is controlled and the beans are kept moving. What am I missing here?
Ideally, yes, but what temperature are you controlling?
On the commercial drum roasters, the probes are designed with certain bean mass in mind. Anything more or less, the measured temperature will start to shift (eg. 1st crack temp will be different depending on the batch size). This is due to the fact that the probe is measuring a combination of bean surface temp and air temp. And below certain batch size, the probe will barely be in contact with the beans at all during roasting - this pretty much throws any roast profiling out of the windows.
And as for keeping the beans in motion - again, the agitator fins are designed with certain bean mass. Having too much or too little, the path of the bean motion will be (drastically) different, which results in the beans being heated differently that alters the roast behavior.
Drum agitator design and bean probe placement is more complex than that meets the eyes....
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