How Low do you go?

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Postby rojo » Mon Nov 18, 2013 10:26 am

Hey folks,

I have a question to pose all. Minimum batch sizes? I'm on a 25Kg Probatone currently, so roughly 50lbs is capacity for us. But when it comes to filling minimal orders or doing some special lots that we don't want to turn into unused coffee that gets stale and wasted, we do a minimum batch. We've toyed with the range some, not moving under 20% the capacity.

We have run into less desireable results when bringing some of these coffees to the table. It seems that some coffees are are losing out on conductive heat with all that room and extra air to toss around in. The end result seems not so much dried out, but that the coffees can kind of fall off quickly after a couple days, once fully settled, they can be lackluster compared to what we expect. SOOooo, we inhibited the airflow some with some mixed results. I think the main issue is with conductivity: bean to bean contact and weight that improves contact with drum and faceplate.

What say you all? Is there a threshold you've found on the low end for charging a roaster? 50%? 30%? I'd like to get at how much and why and what you found that brought you to that decision. Thanks gang.
rojo
 
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Postby charlieblasky » Tue Nov 19, 2013 10:01 am

I love this topic!
I also run into this issue, as we roast to order. I can't say with any certainty what would be the best minimum batch size, but here is what I have noticed:
There is an undeniable correlation between batch size/ roaster capacity, and the final outcome of the product. Not only do I attribute this to the changes in air flow and heat transfer, but also to the ability properly control the roast. When it comes to batch size, I notice that I feel 'confident' in my ability to control the roast at roughly 20% of the roaster capacity. Does this produce an ideal roast? Not exactly, but it is a marked improvement from smaller batch sizes. As far as being confident that everything is going well in terms of heat transfer/ air flow/ other jargon, I have noticed the best results begin at batch sizes above 50% and peak at the 70-85% range. This is on a roaster which I have very little control over the behavior of airflow and heat transfer other than changes to the batch size.

There is an old thread on the board which you may find helpful. It addresses a similar issue.
http://forums.roastersguild.org/viewtopic.php?f=5&t=309&p=892#p892

Hope that I've provided some food for thought.
Kindest regards,
Charlie
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Postby rojo » Wed Nov 20, 2013 12:52 pm

Yeah, I wrote on that one way back when.. I experienced trouble back then with full capacity batches. Funny now I'm looking at the other end of that.

So, I wanted to add part 2 to the question: If one does do a very low weighted batch size like 20%, what adjustments if any do you make to compensate for the added airtime the beans are getting and do you find it works a lot or not? I think a too small batch is just that maybe, and even lowering the damper on the airflow won't really help, instead may just provide slightly more hangtime for smoke and chaff. But I'm theorizing cause I haven't been able to experiment too much with it.

any thoughts?
rojo
 
Posts: 89
Joined: Tue Mar 02, 2010 2:48 pm
First Name: Ryan
Last Name: Gonzales Johnson
City: Brooklyn
State: NY
Zip Code: 11215
Company: Portland Roasting
Occupation: Roaster/QC
Roasting Since (Year): 2007
Location: Brooklyn New York


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