Roasting Different Batch Sizes of Burundi on the Behmor 1600+

Roasting Different Batch Sizes of Burundi on the Behmor 1600+

September 20, 2019


This blog post is about taking a coffee to the same roast level but at different rates of development. When you think about it, roast level tells you very little about how a coffee was actually roasted. It gives you an idea of exterior color, and perhaps a ballpark on roast range. But that's about it. Two coffees of identical roast shades can taste quite different, and it's the roast dynamics that happen along the way that determine how these coffees taste - factors such as batch size, heat changes, air flow, and roast length to name a few.


Using the Behmor 1600+ roaster, my two options for altering roast time are either by manipulating heat settings in manual mode, or by adjusting the batch size. I know I can achieve a relatively fast roast time with 100g of coffee at full power (P5 - 100%), so I decided to go the latter route. Settling on 100g and 200g roast batches for this test, I figured that doubling the batch size would extend my roast significantly. I was not disappointed!


We've spent the last week roasting through all of our in-stock Burundi coffees, checking cup quality and looking for where the proverbial "sweet spot" lies in each. While not all benefit from a light and bright approach in the roaster, many of them do, including the coffee I roasted - Burundi Kayanza Gakenke. It's a dynamic cup when roasted light, and I hoped any differences in dynamic flavors would be obvious in the cup.


Minute by minute roast logs of my 2 test batches


What stands out to me in my notes are roast time and moisture loss. At 200g coffee, Roast #2 went 3 minutes 15 seconds longer than the 100g batch of Roast #1 and there's less than a 1% moisture loss difference between them. I was surprised how close they tracked given the wildly different roast times. But visually, roast levels looked practically identical. And while 1% is a fairly insignificant amount, the differences in the cup were notable.


Roast #1 had a delicate floral aroma and was tea-like in body and with a tannic finish. A tart citrus hint cuts through complex flavors of clove and black teas...a surprisingly bright cup! Roast #2 was a little less dynamic though far from flat. There were still so many positive flavors noted - Darjeeling tea, chamomile, sweet citrus - but it was as if someone shaved off the crisp edges of flavor definition, producing a much more rounded cup profile.


The flavors evidenced in the different cups seem to support our feeling that Burundi coffees benefit from lighter, faster roasts. When roasted this way, body is light but acidity bright, and delicate top notes are the focus. If I had to choose a favorite, I'd go with Roast #1, but I tend to go for outlier flavors and 'punchy' acidity. Roast #2 was still super delicious and I'll venture to say will appeal to those looking for a somewhat more subdued cup. But honestly, if "subdued" is the goal, you should look elsewhere, because Burundi Kayanza Gakenke is anything BUT "subdued" at almost any roast level.