Roasting Question RE: tipping of beans

[Becca]

Hi there, I am a pretty new roaster (350 roasts) roasting coffee for the people living on a small island in BC Canada since February. I have a small (3lb) Sivitz roaster that is doing a good job of things albeit a bit labor intensive, and I have a question about one of the inconsistencies I am finding when I roast. What causes excessive \"tipping\" of the beans? I find that some batches of the same origin, using the same timing \"tips\" more than the others. Some times I will get only a bit of waste and other times I might have a few ounces, and those ounces add up. My air flow is the only variable, but it is very consistent as my timing only varies by seconds. Could anyone give me some insight to this? Thanks a lot. this is my first post to Coffee Forums, but I have been reading the posts and threads. Lots of good info here

 

[ElPugDiablo]

tipping is usually due to excess heat, here is an article about it - for drum roaster, but I imaging it applies to Sivitz too.

http://www.bootcoffee.com/roastinghandbook1.html

 

[Davec]

If your getting the scorching with an air roaster there can be a couple of reasons or a combination of them.

1. If you roast at too high a temperature (max temp), then the beans can tip and you generally get a poor roast. If your getting this Tipping then it's well worth trying a longer roast, but at a lower temperature....

2. As the beans expand during 1st crack their size increases, this affects airflow (they trap more of the available heat). If the heat input to the roast is not reduced at some time during 1st crack, you can often get scorching....as the weather gets warmer, this heat reduction can be much larger than in cold ambient conditions.

Note: it's also more difficult in warm ambients to roast larger loads without scorching than when the weather is cold.

So one or both of the above might be causing your problems, and will certainly affect the taste of the finished product. You don't give any clue as to your 1st crack times, 2nd crack (if heard) times and total roast times, nor the temperature profiles you are roasting with. So my answer is based purely on guesswork and I can only guess at the controls you have available on the Sivetz.

 

[Becca]

Thank you for the responses to my question. Davec, for a bit more info re: my roasting. With the Sivetz, my air flow control is the only variable I have as the heating elements are either on or off. The premise with a fluid bed roaster such as the Sivetz is that the air flow which comes from below the beans causes the beans to spout upward thereby creating a constantly moving load of beans. I can increase the heat by turning down the velocity of the air. I reach first crack at 400F in 9-10 minutes and then to the beginning of second crack at 450F at 12 minutes. If I am doing a med. roast it is just into the second crack and if I am doing a dark roast (french) I finish the roast at about 13min. at 475F. I am seeing that it might be too fast to the second crack. I have the tendency to slow down the air more after the second crack because the beans are now of course bigger and spouting fairly close to the top of the roaster and will go right on out onto the floor if I don't watch it very closely. I may need to try a slightly smaller batch so I don't have to do this. I will give that a try so I don't have to turn down the air so much toward the end of the roast. If you have anything else to add regarding the info here I welcome it. I have been roasting some good coffee and apparently others think so too, as the sales are brisk, but knowing how much I don't know is daunting. At least with this roaster, it very experiential, so I have learned what the beans are doing at each temp on the way up. "Be one with the bean" is my motto. Thanks again.

 

[Davec]

So with no heating element control, you have to turn the airflow down....thus increasing the heat....exactly what you don't want to do, especially in warmer weather and no doubt the cause of your problems.

Reducing batch size should help, although an independent variac based control of the heating element might be worth trying?

The very fast roast times are probably not great for the taste, as by definition the coffee will be getting quite hot (hotter than it needs to), something to really avoid.

It could even be worth investigating whether you can run the whole machine on a variac, to allow you to trim the voltage and thus slow the whole process down?

Or if business is very good and picking up, perhaps a nice 3-5kg gas powered drum roaster would be worth thinking about.

 

[Becca]

Thanks so much, Davec.
I will play around with this some more because I think I know where I am causing it to get too hot.

You are sooo right about the need for the larger roaster. It would definitely be better for me as I still have a full time job and am spending a lot of my time off roasting, which is great that I have the business, but it doesn't make any business sense at all. It is just making the leap and also finding the $$.

I really do appreciate the information and also that you took the time to share your expertise.

 

[Colin]

Just a thought on this issue, although you may have already worked it out. Since the smaller electric roasters that Sivetz sells have no inlet air temperature sensor, it may be worth it to put a thermometer or a thermocouple right at the inlet to see how it changes as the roast proceeds. It may be worth it before you buy any variac based controls. Anyway just a thought.

 

[Becca]

Hi Davec, I just wanted to let you know you were RIGHT ON with the solution to the tipping. I reduced my batch size by about 80grams and kept the air going about 10 points higher on the Variac and it almost eliminated the tipping entirely. Thanks so much!