Fedele article on VST filter baskets, dosing, etc. - Page 2

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jc69
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#11: Post by jc69 »

RapidCoffee wrote:For a given diameter basket, a smaller dose needs to be ground finer to produce correct flow, and a larger dose needs to be ground coarser. For optimal results, you need smaller diameter holes for the smaller dose, and larger diameter holes for the larger dose. Too few/too small holes will cause underextraction, and too many/too large holes will cause overextraction and sediment in the cup. Thus the basket geometry, hole size, and open area must be tuned to the coffee dose. Or so the article claims.
Actually, the article states only that cumulative open area is relevant. Whether this is matched by changing hole number or hole size is not constrained, except for the holes not being too big to limit non dissolved solids.
RapidCoffee wrote:But your question is a good one: what happens if the dose is varied more than +/- 1 gram for a given basket? Can you still match the extraction yield and TDS for a given brew ratio?
In the text it is really said that one should not change the dose at all. It is fixed by basket together with ground coffee density. Of course you can do that (as with any other basket), the new point being that there is no need to do that.

MoJo
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#12: Post by MoJo »

RapidCoffee wrote:
The curse of being a natural proofreader:
Either the column headings or the numbering scheme in the table immediately preceding Figure 13 are reversed for ristretto and normale extractions.
Yes, the column heading Normale and Ristretto are reversed, which I think was/will be fixed in the online version, but may not have made it to the print version in time.

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RapidCoffee (original poster)
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#13: Post by RapidCoffee (original poster) »

jc69 wrote:Actually, the article states only that cumulative open area is relevant. Whether this is matched by changing hole number or hole size is not constrained, except for the holes not being too big to limit non dissolved solids.
...
In the text it is really said that one should not change the dose at all. It is fixed by basket together with ground coffee density.
I believe you are correct on both counts.
John

MoJo
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#14: Post by MoJo »

jc69 wrote:Hi, I've read the article now several times and there's one point I simply don't get.

The claim is made that the new filters should be used in a well defined way only, i.e. the dose in the filter is to determined by the volume of the coffee grounds in the filter before tamping. Then a statement is made that, using this method, you more or less reach the same spot in the brewing control chart independently of the net capacity of the filter (by stopping at the target brew weight given by the brew formula).

That is great for consistency, but you'll obviously limit yourself to a line in the chart, at least for a given coffee.
Hi Jan:
Sorry if this was not more clear. If the [fixed] volume of a given filter is, say 40cc, and it is sized nominally at 20g capacity, that [20g] is meant to be the lower limit. This assumes in practice either a blended espresso, which often includes some lower density coffees, sometimes in Europe can even include a percentage of robusta) or a low density espresso, either by type or roast degree which can affect final density. These coffees have densities in the range of ~0.50g/cc. But, many higher quality S.O. coffees or high elevation grown types or blends of these have higher densities, up to ~0.55g/cc. So, in the 20g capacity filter, these doses will weigh 22g when filled to the same height. The filter, therefore, will tolerate 20-22g, with little change in performance, or 21 +/- 1 g. However, once you start to exceed more than about +/- 5% of a filters nominal capacity, then you will start to see significant changes in the behavior of the filter.

Regarding the brew formula line, no, there is not a limit to a specific line, or EBF (Espresso Brew Formula). The same filter, dosed the same way can be used for any common brew formula, as is indicated on the Fig 13, where you can see each of three different filters being used to extract three different brew formulas at approx 33, 50 and 66%. In this case, the grind was set for the 50% EBF and ~9.5-10% TDS, and left set, only the shot time, by beverage weight, was changed for the ristretto and lungo pulls. If I were to have taken 5-10 shots at each setting, each EBF would have been tightly clustered in the same general region, as long as my technique was relatively consistent. As expected, the longer shots are more extracted, the shorter shot less so. I was fascinated to test the Illy francis/francis last summer and again in January at the European Coffee Brewing Center at Oslo, with standard settings for normale, ristretto and lungo. They landed squarely in the same region of the chart, which was both a surprise and a welcome confirmation of the general targeted area that others on this forum had been advocating for years.



I don't understand your comment/question regarding taste. In general, I find personally that most espressos roasted to a medium or medium light roast profile taste very sour [to me] at 14-16% Extraction Yield, start to taste acceptable at 17%, and taste sweetest [to me] at 18-21, so personally I target 19.5% as a nominal target for extraction yield. Your taste may be different, and so the software (both MoJoToGo for iPhone and eMoJo) allow you to turn OFF the indicated preference region(s) and define your own preference for both strength and extraction yield, as these are personal preferences. However, that said, most people w/in the industry with whom I have had the pleasure of cupping coffees or tasting espressos agree that below 17 starts to become decidedly sour, and above 21 begins to start to taste sharp and bitter. Hope this helps to clarify your question(s), -V

MoJo
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#15: Post by MoJo »

chang00 wrote:Vince, thank you for the reply to the questions John raised.

What I noticed in the past few months of using weight to measure both espresso and drip coffee is, the elixir continues to lose weight on the scale within seconds. The fresher the coffee, subjectively the faster the loss. Presumably it is due to the fast loss of the carbon dioxide and various other gases, in addition to water vapor. How is the loss accounted for when TDS/TBS is calculated? For brewed coffee, sometimes I can observe a 6g loss every 200g.
Hello Henry, and thanks for your comments.

That is a very large change in weight. In coffees that are 4-10 days post roast, then ground, then brewed (for drip) most remaining CO2 exits the coffee during brew, due to the catalyst of both the hot water and agitation. I am guessing, not knowing how you're making these measurements, that you're either brewing coffees that you just fresh roasted at home, which may contain CO2 much greater than typical (2% by weight), or there is a temperature affect causing your scale to drift. You may need to insulate the hot beverage from heating the base of your scale, and re-zero the scale.

As an example, I just brewed a 55g dose with 800g brew water in a technivorm glass model (with top inserted) of Intelligentsia Rwanda Zirikana, and ended up with 705g of beverage that measured 1.54% TDS (19.7% Ext Yld). Measured again, five minutes later, the beverage weighed 703 grams and measured 1.55% TDS, a negligible change. So I'm not sure how you're ending up with a 3% loss within seconds, and therefore suspect possible temperature affects with your scale.

When measuring espresso, the shot is terminated by weight, then stirred to eliminate the natural stratification of concentration. The espresso is tasted, then sampled using a syringe. If you then watch the sampled espresso, you'll see a bubble of CO2 form in the syringe as more COs diffuses out of solution. Then attach the luer-lock filter and operate the plunger. I'm not sure of the mechanism, but have noted that the process of filtering the espresso not only removes the non-dissolved solids, but seems to also have a degassing affect, because no additional CO2 can be observed if the filtrate is then placed into a capped syringe filter*. The clarified filtrate is then discharged into a clean, dry glass @ ambient temp and allowed to rest for 15-20 seconds to equibrilate, then transferred to the sample well of the refractometer, and finally measured. When compared to the TDS obtained by dehydration oven, of the same sample, filtered identically, coffee refractometer readings will typically be within +/- 0.01% of dehydrated samples, which is about as close as the scales in most dehydration ovens are capable of (accuracy and precision wise). Finally, the sample may be saved for hours or days, by using a luer-lock cap, which prevents any air from affecting the filtered sample, and repeated checks of % dry substance by either refractometry or by dehydration will continue to track and provide consistent results.
It is also interesting to read the VST instruction on filter and espresso sample preparation for refraction reading: "Change filters when flow becomes slow or resistance becomes excessive. Generally, one filter is required for each measurement."
One filter is required per measurement. Otherwise, the first sample will contaminate the concentration of the next. Some users might try to filter 10mL or more to dehydrate via microwave dehydration and compare to refractometer readings, for example. Because some filters tend to clog when more than 10-mL is filtered, that is the reason for the statement to change filters if flow becomes slow, it is meant to apply to the same sample. However, only a 0.5-mL is required to make a refractometer measurement.
As previously mentioned, publishing scientifically may not be your goal, and like John, who is a university professor, if you ever need another proof reader, in the medical aspect of the articles you mentioned, perhaps I can be of service....
Thank you. I agree with both you and John, somehow the reference section got truncated, and I should have caught it in the proof. There is a decent medical reference section here that I intended to include from Hilbrich:
P. Zock, M. B. Katan, M. P. Merkus, et al., Effect of a Lipid-Rich Fraction from Boiled Coffee on Serum Cholesterol, Lancet 1990; 335:1235-7; H. Heckers, U. Gobel & U. Kleppel, End of the Coffee Mystery: Diterpene Alcohols Raise Serum Low-Density Lipoprotein Cholesterol and Triglyceride Levels, Journal of Internal Medicine, (J. Int. Med.) 1994; 235:192-3; R. Urgert, A. G. M. Schultz & M. B. Katan, Effects of Cafestol and Kahweol from Coffee Ground Son Serm Lipids and Serum Liver Enzymes in Humans, American Journal of Clinical Nutrition (AM. J. Clin. Nutr.) 1995; 61:149-54; W. Weusten-Van Der Woy, et al., Identity of the Cholesterol--Raising Factor From Boiled Coffee and its Effects on Liver Functions Enzymes, Journal of Lipid Research (J. Lipid. Res.) 1994; 35:721-33; E. Arnesen, N. E. Huseby, T. Brenn & K. Try, The Tromso Heart Study, Distribution of, and Determinants for, Gamma-Glutamyl Transferase in a free Living Population, Scandinavian Journal of Clinical Laboratory Investigation, (Scand. J. Clin. Lab. Invest.) 1986; 46:63-70; O. Nelssen, D. H. Forde, & T. Brenn, The Tromso Study. Distribution and Population Determinates of Gamma-Glutamyl Transferase, American Journal of Epidemiology (AM. J. Epidemiol.) 1990; 132:318-26; Ulmann's Encyclopedia of Industrial Chemistry--5th Edition, 1986; Vol. A7:pg. 334; M. Van Desseldorp, et al., Cholesterol--Raising Factor from Boiled Coffee does not Pass a Paper Filter, Arteriosclerosis and Thrombosis 1991; 11:586-93.

I hope that answers your questions, best regards, Vince.

*similarly in brewing of beer, initial potential alcohol is determined partly by a measurement of % sugar of the wort. This measurement can be by hydrometer or by refractometer measuring mass fraction of sucrose in solution (g/100g) or the older term "BRIX". Similarly, CO2 that is present must be removed before either hydrometer or refractometer will yield accurate results, and in the case of the refractometer, non-dissolved solids must also be removed.

cpreston
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#16: Post by cpreston »

MoJo wrote: The same filter, dosed the same way can be used for any common brew formula, as is indicated on the Fig 13, where you can see each of three different filters being used to extract three different brew formulas at approx 33, 50 and 66%. In this case, the grind was set for the 50% EBF and ~9.5-10% TDS, and left set, only the shot time, by beverage weight, was changed for the ristretto and lungo pulls.
I have to admit to being totally confused. If I read the article correctly, the only thing the user needs to do in order to move (with same dose) from a lungo to a ristretto is to shorten the shot time, with the grind being left alone. This does seem like a very convenient way to do it.

But I had always understood that classically to move with same dose from lungo to ristretto one tightens the grind and LENGTHENS the shot time, with the exact timing determined by the flow color or a surface tension indication like a cone collapse.

These two approaches seem radically different and would only coincide for one brew strength or EBF. Can someone set me straight on this?

King Seven
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#17: Post by King Seven »

The approach of changing brew weight with a consistent dose is interesting and does work well with the filters. However - if you're dialed in for a 20% extracted espresso, you can't get a matching extraction as a ristretto unless you change the grind. You can get a well extracted ristretto (18%+) with just shot size adjustments.

The wider implication (that I most enjoy) is a larger window of tasty in your shot brewing - essentially you'll see a higher level of tolerance with the baskets and less sink shots.

Disclaimer: I've had some of the 21g VST prototype baskets to play with for a little while though I have no financial interest in the product.

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cpreston
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#18: Post by cpreston »

Thanks very much, that clarifies it.

Now I'm wondering which property of the new baskets is responsible for "a higher level of tolerance with the baskets and less sink shots".

Optimal nominal hole diameter?

More consistent hole diameters as per histogram?

Or the claim that the open areas are optimized correctly for the center of the desired extraction range and therefore have enough wiggle room on either side? (One might presume that existing baskets would be similarly tuned, but apparently this is not always the case.)

jc69
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#19: Post by jc69 »

Hi James,
The approach of changing brew weight with a consistent dose is interesting and does work well with the filters. However - if you're dialed in for a 20% extracted espresso, you can't get a matching extraction as a ristretto unless you change the grind. You can get a well extracted ristretto (18%+) with just shot size adjustments.
the question to me is whether it would really make any sense to move to a ristretto with the same extraction. I'd expect, in order to get a balanced ristretto, you'd be forced to go near 18%.
In that sense, it starts to make sense to imaging extraction as a path in the brew chart, evolving in time or brew ratio. I never thought of the possibility that larger parts of the path might be balanced (at least roughly).
Regards, Jan

King Seven
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#20: Post by King Seven »

It would make sense if you enjoy the combination of beverage strength from a small espresso (brew ratio of 75%+), with the balance and complexity of a well extracted portion of ground coffee (20%).