This question came up in the
Coffeetime forum and I think it's worth making it a small article on the
Coffeetime website
When I roast I tend to pre
roast blend, and when dealing with commercial roasters I have found most do the
same. But the idea of post blending still appeals - you can choose the roast
level for each origin to get the best from them - and then combine them in a
post blend for a supercharged espresso - anyone got any thoughs or
pros/cons?
Well commercial roasters do tend to pre-blend and roast
it all together in the drum.....I have seen comments like, they "feel" it
"hangs" together better and the roast tastes better etc..
Having been
exposed to a bit of commercial roasting, the reason I was given, and this makes
much more sense to me, is...with a 25kg batch, it mixes properly in the drum of
the roaster and it would be very hard to mix it later. It's purely a convenience
thing, although I think roasters trying to convince you of some "magical"
techniques, would like you to think otherwise.
Also if you have a 25kg
roaster and a blend of 4 beans, you have to roast a minimum of 25kg each batch.
Say your blend was
10% Robusta 20% coffee A 30% coffee B 40%
Coffee C
To post blend, this would mean roasting 25kg of robusta, of
which you would only use 2kg in your blend. Now unless you needed 200kg of
espresso blend.....what do you do with the rest of the robusta (same applies for
all the other coffees). Oh weights don't add up mathematically cos accounting
for up to 20% weight losses on roasting.
All beans don't roast to the same level in the same
time....thats it nothing more to it than that. Logically this means that any
blend will contain beans roasted to different and possibly sub optimal levels. Any
roaster who tells you otherwise, is fooling themselves. Now you could limit
yourself to blends that contain beans that all roast to the same level in the
same time, or beans that taste good roasted to differing levels. This does
however limit what you can have in a blend. So they don't limit themselves and
"cup" it to see what tastes best.
However, convenience and
practicality is the name of the game.
For the home
roaster, or the smaller roaster (and I mean small), post blending makes far more
sense. This is because your batch sizes are very small and mixing the beans
afterwards is not such a huge problem as with 20 kg batches. You will also not
have so much wasteage, but would have to think quite carefully if you wanted to
bother with 10% robusta. e.g. in my roaster it would mean having a Kilo of
robusta of which I used mabye a few hundered grams....the rest would go stale by
the time I next roasted. Solution....I don't use robusta. It also of course
means you can't use those busy and impressive sounding 7 bean blends so easily,
because you have a LOT of coffee going to waste to create a rather silly 7 bean
blend for espresso. e.g. 7kg roasted, to make 1kg of espress blend.
If a
commercial roaster tries to creat new blends by post blending, then the flavour
of the same blend "must" be very different when pre blended before roasting!.
For the home roaster, in a different way,
convenience and practicality is also the name of the game . You decide to
roast 3 small batches, some you keep as single varietal beans, some you post
blend.....all of course roasted to their optimal level. This means that your
blend is likely to taste better, but more difficult to experiment with the more
"exotic" blends containing lots of different types of beans.
In addition
for the home roaster, if you roast the right 3 or 4 beans, then it's easy to
create a few different blends from the same batch, also a great way to
experiment with new blends.
Conclusion
In both cases
it's a practicality issue.
Commercial roasters can use/create
more exotic blends....but unless beans all roast the same way (and almost
certainly they won't), the roasts will be a compromise on potential for flavour.
Home and V small roasters (post blending), can use prehaps less types of
beans in a blend (for practicality), but can ensure each bean is correctly
roasted....maximising potential for flavour.
I tried to express this
view on another forum, but was quickly squashed before the discussion could get
going and never got the chance to put my reasons in full. So here they
are.
