Almico wrote:I'm not a big fan of light-roasted espresso so I really don't have a dog in this, but as far as SO blends go, I would guess most SO coffees are blends. Not necessarily blends of terroir, but certainly blends of variety. And coffee variety has much more to do with the characteristics of a coffee than the country where it was grown.

A roaster I used to buy from offered what he considered to be a SO blend as he sourced the coffee from Brazil (Ipanema region) and roasted half the batch lighter, half darker, then blended post roast. That gave outstanding qualities of both ends of the spectrum and balanced quite nicely.

What I've gathered so far:
1) It is possible to roast coffee in a manner that can produce (what I interpret as) sour tasting notes.
2) This can even be traced back to the greens.
3) Lots of ways to control sourness in the espresso brew, and they work.

I OP'd in the roasting forum to focus on the roasting side of the equation:

Is a roast sour because it's too acidic - or was it lacking the sweetness to counterbalance? I get the answer may be "both", but does that lead to contrary roasting profiles?

I gather the browning phase caramelizes sugars in the greens, but do those sugars taste sweeter before or after caramelizing? I have experimented with short versus long browning phases (keeping everything else the same) and the shorter (less heat energy input) roasts did seem more acidic - but perhaps the longer browning time simply reduced the acid.

I also gather that the development phase (post first-crack) is the heavy-hitter for acidity reduction - but comes at the cost of increased bitterness and 'roasty' notes. Could I use the drying and browning phases to manage the acidity instead? FWIW, I tried dehydrating a batch of greens (roughly per SCA guidelines) prior to roasting, and the resulting roast was one of the least acidic I've experienced, but also kinda 'boring'.

Here's my take. Sugars taste less sweet when caramelized. It can be confusing to think of cooking analogies where you are also concentrating browned sugars. You can greatly reduce acidity with a longer Maillard phase and converting acidity to other flavors happens as heat continues to be applied during the roasting process. Roasty notes don't typically occur with a steadily declining BT ROR. Taking a roast really dark can increase bitterness as you're burning the coffee. Taking it into 2C can produce roasty notes, but maybe others can tell you whether it's the chemical reactions that invariably occur at certain temperatures or whether you don't have roasty notes if in early 2C with a steadily declining BT ROR. Alan would know this. It's a difficult profile for me to manage, so far.

So, cane sugar (C12H22O11) tastes sweeter than its caramelized state - but is that still true for the 'sugars' in a green coffee bean? There's more than one version of CxHxOx that qualifies as 'sugar' and they may not taste as sweet as cane sugar - or their caramelized counterparts.

Wet versus Dry caramelization:
Wet caramel is made with a sugar+water mixture that extends the cooking time and can (allegedly) create a richer caramel flavor. I mention this because I've been experimenting with driving the greens above the caramelization temperature as fast as possible, under 90 seconds. My (hairbrained?) theory is water trapped deeper in the bean will interact with the caramelization process on the exterior of the bean, moderating the process and (hopefully) minimizing the risk of burning as the caramels develop.

Are you saying you're going from charge to end of drying in 90 seconds - taking BT to about 320F? I would stay within common roast parameters of about 4-5 minutes to end of dry. Oh, you're on an Ikawa. What's one of their standard profiles do? Looking at one online I see that your target is plausible, but it's outside my experience.

You're probably aware you're building many atmospheres of pressure within a matrix of cells, so you're pressure cooking with heat applied to the bean surface.

I have a thermocouple positioned in the spinning bean mass in the Ikawa's roast chamber, but I wouldn't call that the same as the BT reading in a drum roaster, given the airflow is over an order of magnitude higher in the Ikawa. That said, it's pretty easy to drive the exterior of 50-60g of beans to 340F in 90 seconds, which is similar to Ikawa-curated profiles.

So yeah, I suppose it is a bit like a pressure cooker That might explain a very faint crackling sound I hear during the latter half of the browning phase.

One thing that I don't think has been mentioned is that you may not be able to think about sweetness in a vacuum. I distinctly remember from a discussion with a cupping instructor at a class I went to a while back that the perceived sweetness of coffee is as much a function of contributing factors that trick one's brain into thinking it is sweet as it is actual sugar being sweet. For example, a note of ripe strawberry in a cup of coffee combined with the right balance of sour/bitter, body, and acidity can trick the brain into tasting a sweeter taste than is actually there because of one's taste experience. The brain expects ripe strawberry so it colors in the rest. He noted that clarity is important for the trick in his experience. Which makes sense, the closer to a "sweet" flavor the coffee gets without negative attributes the more readily the brain would fill in the sweetness. At least, that is the idea.

His comments stuck with me a bit and I can't speak to them with any authority but it is something I keep in the back of my mind when tasting coffees with distinct notes. An interesting point of view that I thought I'd share.

Milligan wrote:the perceived sweetness of coffee is as much a function of contributing factors that trick one's brain into thinking it is sweet as it is actual sugar being sweet.

Exactly - thank you! I wonder (translate: would like to know) if the same holds true for sour: if there's something in the roasting process that combines with acidity to make sourness.