In my view, sure it's a perfectly good way of making something like espresso with good extraction, what a lot of coffee people call these days a turboshot. But it's not really providing what people usually want in an espresso: a concentrated, textured small coffee.
i definitely don't drink a lot of dark roast espresso, but i think a turboshot has no problem producing adequate texture.
If you take a purist definition (9-10 bar extraction pressure) then some of the papers testing falls outside the definition.
If it tastes different and is made in a new way, shouldn’t it get its own name?
I can't recall the exact official definition but it's something like: 7g of coffee extracted under 9 bars of pressure at 94C yielding 14g of liquid.
It's extremely limiting, for example it's designed for dark roast and isn't ideal for medium/light specialty coffee where you might have to adjust the temperature and yield to get good results.
Modern high end espresso machines these days are starting to allow you to play with the variables and in the espresso community it's usually considered that anything over 6 bars is an espresso. Also, other techniques like pre-infusing at 1-3 bars before ramping up the pressure is common. Personally I'm partial to a long 20s pre-infusion at 1 bar before ramping up to 6-7bars. This yields a very sweet shot with a medium roast bean.
Pre infusion aside, the article starts at the low end of your definition but does have graphs that go as low as 4 bar.
That’s almost at the stage of being made using the pre infusion only, and perhaps I should try that as that’s down there.
I prefer a thick crema (for look and taste) but I’ll try drop the pressure down and see if I’m persuaded.
Regarding your long pre infusion - how much of the shot is being extracted after 20 seconds? I’d expect a good 5-10ml by that time but maybe your pressure is so low that little comes out.
Basically zero, maybe one or two drops. You need to grind finer though and you need a grinder capable of that. A decent hand grinder is ok (e.g. 1zpresso jx pro or max) but for electric grinders you're into the $600+ range before you can do it, e.g. a specialita or a niche .
That high pressure causes some odd taste notes and it would cause channeling in the puck. Not to mention all sort of other issues which start already at ~11 bars.
I found this article interesting because they talk about the complexity of espresso as being characteristic of a mix of extractions at different pressures. This is apparently different than the model they came up with to brew the perfect espresso. But they also note that 9-11 bars is too high and go as low as 7. Fascinating.
I strongly believe that the Nespresso was designed to solve/create a problem to fit their business model.
In this order: Proprietary, good margin, small foot print (pods and extraction unit), easy to use, disposable.
That said, another thing which plays a big role in the resulting pressure is the design of the brewing head and the design of your basket. Baskets can be either pressurized (they have a single hole through which the coffee will flow) or non-pressurized (they have a lot of small holes through all of which coffee will flow). You can imagine that the resulting pressure will depend on the type of the basket you're using.
Because cheaper appliances will by default use pressurized baskets, they will tweak the pump to some pressure level which they found to work the "best" for their type of machine and that level is exclusively much more than expected 9-10 bars. Nespresso will for the same reasons do the same with the difference that they make one step forward to take over the full control over the puck preparation process through their prepackaged pods.
Espresso machines without OPV are really a minority. Even single-boiler entry level machines like the Gaggia Classic or the Rancilio Silva have an OPV.
Gaggia Classic is a 350 EUR machine whereas Rancilio Silvia is 600 EUR machine. These are not entry level machines. They are entry level for someone becoming more interested in espresso but not for ordinary people. And ordinary people do not spend 400-500 EUR for a coffee machine if they think they are going to get the same for twice less money. Twice less money machines do not have OPV.
Yes they are. To put some perspective, my current machine (Bezzera BZ10) costs about $1,700 USD and it's not even close to being a high end machine.
Respectfully, you don't know what you're talking about. Even the Delongi Dedica, which is at the bottom end of espresso machines, has an OPV valve.