DavecUK Senior Member Joined: 21 Sep 2005 Posts: 1,404 Location: UK Expertise: I love coffee
Posted Fri Dec 21, 2012, 4:08am Subject: Re: Optimal pressure for good extraction?
It's a tricky question. The optimal pressure depends on a number of factors e.g. puck depth, point within the shot, temperature and probably even the type of coffee. Some Spring levers can make an interesting shot because their pressure profile is not constant throughout the shot. Many times I have heard and experienced better results by a reducing pressure profile as the shot progresses. This makes sense in the context of increased undesirable flavours as the end of a shot is neared, lowering the pressure seems to help prevent these being extracted.
It is definitely the case that lower pressures on a standard espresso machine "softens" the shot, higher pressures make the shot "harsher" e.g. 8 bar on a Duetto (or any other machine) and 10 bar. This is again affected by temperature, my experience has been that at higher temperatures, lower pressures are better tolerated and have less "softening" than at lower temperatures. Whereas high pressures and high temps can make for a very harsh shot.
Pressure profiling may well be the method by which future big incremental changes can be made shot quality.....initially by being able to select a pressure quickly to extract a particular coffee at, later perhaps defining a profile within that selection.
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