Jake_G wrote:1. What indicators do you look for in a given shot that would suggest that you should increase the brew pressure? How about decrease? Or what makes you think to try a declining profile versus flat?
2. For instance, there's good consensus around brew temperature and roast level. Dark roast, cooler brew temp. Light roast, higher temp.
3. Likewise with grind level and what used to be dose, but now can be preinfusion duration. Darker roasts have historically been coarsely ground and up-dosed, with lighter roasts initially ground fine and down-dosed, but now simply ground fine and softened with a either a long slow preinfusion or a soak phase or some combination of the two. This allows some of the classic rules to be bent if not broken. But what about peak brew pressure? Lets say you have a grind and dose that you like with a given brew temperature and profile. What makes you think "that was great at 9 bar for the peak, I bet the same shot would really shine at 7 bar."? What about 10 bar? This is something I really haven't thought much about, but am ready to dive into now that I have so much more control over the rest of the extraction. My machine has been set at 8.5 bar with my 8mm non-restrictor for the last 5 years. It's likely time for me to figure out what other pressures taste like, but I'm curious if there are some conventions that might guide the would-be traveler in their quest?
The area is complex, so much so that I have few answers after literally years of experimentation.
1. The shot doesn't always give obvious indicators....it's unfortunately a taste thing. However because grind can change (especially if you profile with a slow ramp up), you have to wonder what effect that can have.. The only thing I know for a fact is that straight 9 bar, 8 bar etc.. probably isn't the best profile. Any flat profile was because that's what could be done, not because it was best. A lever gives a declining profile, but again, because that's what it does, not because it's best. The development of a pressure for extraction was a consequence of the technology used. We have different tech now and can do different things. it might be 10 or 11 bar at the beginning of extraction is optimal, reducing as the shot progresses, it might be lower pressures entirely are better.....I don't know for sure, but I have some ideas.
2. There might be good consensus, but again that doesn't make it right or definitive. That consensus was largely reached based on machines that cannot do what they do today. I have experimented with both higher and lower temps on light roasts and I find that too high a temp simply brings out undesirable notes, in the same way as it does on dark roasts. So I buck the trend, but I have to go by taste. I do find that pressure and duration of extraction can make a big difference though. light roasts seem to like a longer extraction and a good preinfusion. I think people often vary temperature to try and make up for a suboptimal roast. I usually extract at 93.5C on my machine. If I change it I will sometimes go as high as 94.5 or as low as 92.5...not often though. Can people taste 0.5C difference, not usually. Roasters should also be creating roasts that extract well at the widest range of temperatures.
3. Grind level again is really tricky. In the past machines were simplE and a certain grind level was required. Machines and grinders have moved on a bit and like everything else grind can vary with the rate we extract pressure, bloom phase, max pressure and extraction time....which of course doesn't have to sit within a rigid zone of 22-32 seconds or whatever. Much longer extractions can be done if desired.
It's hugely complex and I think the whole area needs to be revisited, if it is I think will also affect the way roasters roast. I'm hoping the next wave in coffee is going to really rethink how we produce shots, rather than the rather simplistic dark vs light roasting.