Hi,

Doesn't the volumetric control system go against the "90°C / 9 bar / 25 sec" golden rule ? therefore against the final quality of the espresso ?
I have an old ns mac2000v single group in very good shape and have replaced the volumetric control with a simple 25 sec push button timer and a manual (semi-automatic) erogation release. In this way I have more control over the erogation time (25 sec) and I can control the volume through grinding size and tamping pressure.
I understand that beyond the 25 sec the espresso tends to become bitter because the coal of the toast begins to be "washed" down,
I will very much appreciate for comments.

Thanks

Hello, Antonio

I think it is just that many people who use an automatic machine prefer to leave the volume of the drink as a set amount (especially in a commercial setting) and vary the grind to achieve that within a specified time. Your approach achieves the same thing if you are varying the grind to achieve a specific volume in the cup in a fixed time, although actually none of the "rules" - including time - are absolute (see below)

The definition of an espresso now varies very widely, especially outside Europe, and more particularly, outside Italy. Many people consider the rules to be more guidelines or starting points, especially in a domestic environment, where individuals may prefer espresso brewed well outside those parameters.

To be certified Italian Espresso, the Italian Espresso National Institute has a required definition:-

Necessary portion of ground coffee 7 g ± 0,5
Exit temperature of water from the unit 88°C ± 2°C
Temperature of the drink in the cup 67°C ± 3°C
Entry water pressure 9 bar ± 1
Percolation time 25 seconds ± 5 seconds
Viscosity at 45°C > 1,5 mPa s
Total fat > 2 mg/ml
Caffeine < 100 mg/cup
Millilitres in the cup (including froth) 25 ml ± 2,5

You will see that even in their definition (which is for a single espresso) the largest variation is in the time, and people who do not use any sort of automatic brewing, but who watch the process carefully and stop it when they think is appropriate, may have timings quite a lot different from this standard; so to many people having the time absolutely fixed isn't the best approach.

On the other hand, volumetric dosing can't measure the amount of crema (froth) although in a commercial high volume environment this probably will not vary much from drink to drink.

Hi Rob,

Thanks a lot for the complete explanation, it is then a matter of personal approach how to control the best espresso quality.
Just for clarification to other espresso colleges, the erogation time for one or two espressos is the same, 25 sec +/-, the only difference is the filter holder and the amount of coffee.

Thanks again and best regards

antonio

lucre wrote:... it is then a matter of personal approach how to control the best espresso quality.

Yes - and of course, the real espresso enthusiasts would probably have nothing to do with any kind of automation anyway - neither volume nor time - and would optimise each drink manually, based on their own tastes and experience. For those of us who may not be blessed (or cursed ?) with such a highly developed sense of taste, automation is just something that makes life easier, especially when you are busy. But in any case, most volumetric dosing machines can be cut short manually if you wish.

keepitsimple wrote:Yes - and of course, the real espresso enthusiasts would probably have nothing to do with any kind of automation anyway - neither volume nor time - and would optimise each drink manually, based on their own tastes and experience.

While I agree with the sentiment not the reality. Can you say Vesuvius? Though personally I may well someday upgrade from the fully programmed only profile shot Vesuvius to probably GS3 MP Strada for full manual shot profiling at around twice the price...

I'm sure some folk will still decide that any pre-programmed time/pressure curves can't always be right, but the tinkerers will love it.

Personally, I couldn't cope with yet more variables

(Edited)

Regardless of the machine-manual, lever semi-auto, programmable volumetric/chrono-it's still the same set of variables. Programming, or "automating," any one of those variables as a "constant," while tweaking the remainder in order to hit that target, or simply deciding on what you will "target" and what you will tweak to try to hit that target in the case of manuals, it's six of one, half a dozen of the other. Depending on your machine, we all may take different routes, but we're all trying to arrive at the same place. Shot duration on my machine can be chrono or volumetric. I choose to set it in terms of time. Feels more intuitive to me, only because that's exactly what I was doing with my old lever-actuated E61 Hx machine.

lucre wrote:Doesn't the volumetric control system go against the "90°C / 9 bar / 25 sec" golden rule ? therefore against the final quality of the espresso ?

That's not a rule, it's a generalization. Not a good one, either.

The "generic" right brew temperature isn't a specific temperature but a range of about 5C. 90C is just wrong. The ideal temperature, +/- 1C, for any given specific coffee will fall between 91C and 97C, and more often than not, right around 93C. The ideal brew temp is determined by taste.

The generic right brew time is also a range, 22sec - 32sec. However, brew time is more of a diagnostic than an absolute, and is superseded by taste. If a shot runs 40sec and tastes good, time is not a problem. However, if the shot tastes bad and pull times are way too long or too short you know that grind and/or dose need adjustment.

I understand that beyond the 25 sec the espresso tends to become bitter because the coal of the toast begins to be "washed" down.

Setting aside the reference to "25 sec," unless the bitterness is inherent to the bean, bitter espresso is over extracted. If it was brewed for a very long time, that's at least part of the cause. That can happen with no burnt (coal) aspects to the toast roast.

What we're looking at in your posts is a set of false assumptions which led to a false conclusion.

Because a great shot is dependent on hitting the right extraction level (aka extraction yield) you can't use time, volume or weight of shot as a reliable cutoff.

On the other hand, with a very good grinder used "single dose" style, and very good barista technique, not only can volumetric control be as consistent at repeating extraction level as eyeballing the blond point, it can consistently nail extraction yield within a much tighter range.

By way of example, Matt Perger (a famous barista) has a set of three blog posts comparing the EK43 grinder to other grinders which relied heavily on comparing extraction yield. As far as the underlying assumptions and conclusions go, its problematic. What's of particular interest though, is that volumetric control was compared to eyeballing the extraction level, and chosen for the testing because of its greater consistency

However it's a lot of trouble to set everything up to achieve perfect consistency with volumetric shutoff; and bean aging and weather make the right cutoff point a moving target overnight or even after a few hours. Consequently, many baristas set the volumetric measure a skosh on the high side, using it as a fail safe in case they're distracted during the shot and miss the blond point.

Moral of the story: Cut the pull at the blond point. If your shots are consistently good, don't worry about anything other than finding appropriate pastry. But if your shots taste funny and brew ratio (weight of dose/weight of shot) and/or flow rate is/are out of whack, adjust grind accordingly.

Dose should be appropriate for your basket and machine. If the grind changes the height of the column and head space too much, adjust dose as well.

Note also: Brew ratios are definitional. For example, if you're trying to pull a "normale" and your brew ratio isn't in the vicinity of 50%, you failed.

Rich