This post addresses numerous threads on h-b.com relating to Extract Mojo and VST Baskets. It did not neatly fit any of the existing threads, so I hope Dan will allow this thread to stand alone.

Disclaimer: I have no financial interest in these products, though I do sometimes barter my books with Vince Fedele of VST for his products, and I often recommend them to my consulting clients.

I believe the ways many H-B'ers have approached Extract Mojo (EM) and VST baskets has caused them to misuse or misjudge these products. Many have expressed blind faith in the testing done by others, and have rejected these products out of hand without any personal experience. That is very unfortunate for a group of people who care so much about their coffee. Here's why:

My thesis is: Extraction % is the single variable most correlated to coffee flavor. I say this after having tasted and measured well over 1,000 brewed-coffee samples and over 500 espresso samples over the past few years.

Jim Schulman has stated on H-B (see: ExtractMoJo for exploring the extraction space):

"I abandoned trying to correlate the refractometer levels of extraction to taste features after a week of trying, and getting nothing remotely useful."
and:
"It (EM) fails in fully exploring or controlling the extraction space. It was impossible to predict or predetermine the TDS, total solids and extraction yield from a given grind setting, coffee/water ratio, brew temperature and steep time."

My own experience could not be more different from Jim's*. In fact, my business partner Anthony (a fantastic barista and an equally avid user of Extract Mojo) and I often play a guessing game, usually successfully, in which we taste a brew, guess the extraction %, and then check our guesses against a refractometer. After a few hundred such tries, it has become relatively easy to guess the answer to within +/- 0.2% extraction. This is easier with brewed coffee than with espresso, but is still usually manageable with espresso (This applies to coffee extracted in the range of 18.5%--21%; we don't bother much with extractions outside of that range.)

When I read H-B discussions in which the dose and coffee-making technique are obsessed over in fine detail, and some conclusion is made about a technique or a product, but extraction % is not discussed, I'm dismayed. We would all communicate better and make faster progress in our coffee-making skills if we focus on technique, taste, and extraction %, rather than on just technique and taste. (Please note: I realize many home baristas cannot afford, or will not choose to buy, an EM refractometer; however, that doesn't detract from the value of the tool. )

I have found the range of the best-tasting extraction percentages to be consistent across machines, baskets, coffees, brewing methods, and techniques, assuming reasonable brewing temperature, a relatively even extraction, and a high-quality grinder with sharp burrs. Every time I have had personal contact with someone who disagreed, I found a glitch in their approach (for example, using dull burrs or creating very uneven extractions), that once remedied, led them to agree to superiority of that same range. All of the best professional tasters I'm in regular contact with also agree on that range. (I'll refrain from naming them and dragging them into this discussion.)

So there must be something to it.

As for VST baskets, (see: How filter baskets affect espresso taste and barista technique), the scientific approach Mr. Schulman took in comparing baskets had two tragic flaws:

1. VST specifically recommends using a particular dose with each of their baskets. (for example, a 22-g dose with the 22-g basket.) This manufacturer's recommendation was largely ignored. Unfortunately, with the VST's unusually large holes, using a lighter-than-recommended dose, and hence a finer grind, too much solid material can get through the basket and into a shot. This additional undissolved solid mass no doubt changed the character of the shots from the VST-baskets and may have distorted Jim's perceptions of the shots produced.

2. Espresso shots from different baskets were compared, but no effort was made to measure extraction %'s or to compare shots with the same extraction %. Comparing shots at different extraction %'s to judge baskets is a pointless, apples-to-oranges comparison. As a professional, when I compare different coffee-making devices, controlling for extraction % is always a prerequisite for a fair trial.

VST baskets are perhaps the first commercial baskets to be made with true precision. Prior to having these baskets, I had never found a make of basket that offered perfectly consistent diameter or flow rate, basket-to-basket. Having these baskets has taken several variables out of the equation of dialing in our espresso shots. They've also allowed me to communicate more effectively with other roasters and baristi about a particular coffee.

One caveat: You will get better results and fewer micro-channels if you use a 58.4mm tamper in conjunction with VST baskets; good results can be achieved with a 58mm tamper, but better results will be achieved with a 58.4mm tamper. I do not believe this factor was addressed in Jim's study.

Scott Rao

*I have great respect for the time, hard work, and intelligence deployed by Jim and the other H-B'ers who participated in testing EM and the VST baskets. This critique of their methodology is in no way meant to be a reproof of them personally.

On the Extract Mojo: I have no problem seeing it as a replacement for a TDS meter. I would be interested in seeing how well it correlates to the ICO/ISO lab standard of measuring TDS by dry weight of coffee (i.e. evaporating fixed weight of coffee and weighing the dry residue). The TDS meters sold by the SCAA and used in the studies the Extract Mojo literature cites were calibrated by this method. The Extract Mojo is missing this traceable connection to the standard.

On the VST Basket: I recommend the basket and its clones as a means of making higher dose espresso with finer grind settings. I reiterate that if in basket A the flow changes by one unit for a unit change in dose, and in basket B it changes by half a unit, then the shot to shot variance using basket B will be half of that using basket A. VST baskets are quite sensitive to dose changes and are therefore less consistent in the face of small operator variations.

On the Single Variable Theory: Scott is advocating a new version of the single variable theory: "get the extraction right, and your coffee will be good." We've had this before: "get the dose right," "get the temperature right," "get the roast profile right," "get the grind right."

The problem with the single variable theory is that all the people who say this never actually mean it. What they mean is "do everything exactly as I do it, and then this variable will be the key to your coffee making." In the case of extraction, equally extracted coffee using different combinations of fine and coarse grind, hotter or colder initial water, higher or lower insulation and heat loss, longer or shorter steep times, and different percolation or steeping methods, will all taste different. The best tasting extraction of a given coffee using one method will be different than using an another. "Get the extraction right" presupposes a single way of making coffee is being used throughout. Telling people what percentage is right, presupposes everyone uses the same set of coffees and prep methods all the time.

There is always a sweet spot for all the variables, and the single variable people are, in effect, telling people that all but that one variable are from now on to be considered to be constants. So apparently my whole experiment with flow and baskets was misconceived, since the dose in baskets is to be held at exactly to what the manufacturer specifies. For instance, even when people comment that VST baskets are finicky, it is improper for anyone to run an experiment on how they respond to dose and grind changes.

I compare coffees when I cup. I compare baskets, machines and grinders when I do reviews. I cannot use the single variable theory when doing these comparisons, and nobody who does these comparisons can do so. Instead, I and others use the ceterus paribus principle, i.e., the principle used in all scientific comparisons -- that all the variables except those being compared should be held constant.

My suggestion is that if the apologists for VST baskets and the Extract Mojo think there is something wrong with the approach I used in the basket study, their quarrel is with the scientific method, not with me.

bigabeano wrote:One caveat: You will get better results and fewer micro-channels if you use a 58.4mm tamper in conjunction with VST baskets; good results can be achieved with a 58mm tamper, but better results will be achieved with a 58.4mm tamper. I do not believe this factor was addressed in Jim's study.

Scott, do you mean a 58.4mm flat tamper, as AndyS recommends, or any shape 58.4mm tamper?

(I hope it's the former, as a 58.4mm flat on its way to me!)

I have many thoughts about the debate, which I may share after digestion.

Jim,

I've seen the EM refractometer perform favorably in comparisons with a $15,000 benchtop refractometer and a $10,000 Labwave Microwave/ Moisture Analyzer. Those instruments are probably more accurate than either you or I could be when dehydrating espresso in an oven. And they're less smelly

I don't remember addressing the "sensitivity to dose changes" of VST baskets. What I do know is that when one maintains a consistent dose, one gets consistent results in every VST basket. I am not aware of any other make of basket that can be said of, and I think I've had experience with the majority of basket brands in existence.

As for me being an advocate of the "single variable theory", to be clear: my saying extraction is the most important variable is not the same as saying extraction is the only important variable.

I did write:

bigabeano wrote: We would all communicate better and make faster progress in our coffee-making skills if we focus on technique, taste, and extraction %, rather than on just technique and taste.

(that's three big variables)

and

bigabeano wrote:I have found the range of the best-tasting extraction percentages to be consistent across machines, baskets, coffees, brewing methods, and techniques, assuming reasonable brewing temperature, a relatively even extraction, and a high-quality grinder with sharp burrs.

My three criteria of "reasonable brewing temperature, a relatively even extraction, and a high-quality grinder with sharp burrs" is not the same as "do everything exactly as I do it." I believe those three preconditions are fundamental to a competent barista (dont' you?), and not specific to the way "I do it."

As for scientific method, I love it. . I have no quarrel with you or with scientific method. My quarrel is with the absence of extraction percentage as a variable in your tests.

bigabeano wrote: I've seen the EM refractometer perform favorably in comparisons with a $15,000 benchtop refractometer and a $10,000 Labwave Microwave/ Moisture Analyzer. Those instruments are probably more accurate than either you or I could be when dehydrating espresso in an oven.

Ted Lingle's handbook on brewing outlines the ICO/ISO dehydration standard for measuring TDS. The refractometer cannot compare "favorably" to it, since that is the lab based FDS (fundamental dimensional system) standard. Nor can your method compare "favorably" to any instrument calibrated to this standard, such as the TDS meter sold by the SCAA, until you have traceable evidence that the refractometer actually measures TDS. I believe, as do most people, that it does so fairly well; but at an unknown level of precision and repeatability. You cannot claim more than this until you gather and publish data comparing it to a laboratory reference (for coffee TDS, not moisture, brix, or whatever)

bigabeano wrote: As for me being an advocate of the "single variable theory", to be clear: my saying extraction is the most important variable is not the same as saying extraction is the only important variable ....As for scientific method, I love it. . I have no quarrel with you or with scientific method. My quarrel is with the absence of extraction percentage as a variable in your tests.

My basket study addressed how the flow of espresso responds to dose changes in baskets, since small dose changes happen with any non-weight based dosing method, including those used in cafes. The study found larger than expected flow changes in all baskets, especially the VST ones, since the small changes in dose created large changes in the dwell time.

Please explain how using the same dose over and over again and taking refractometer readings would have answered this question.

On the taste side, I made:

• a shot with 11 grams of coffee and 16.5 grams of water using an LM single on the same machine in the same time and with the same pressure and grind setting as a 17 gram shot getting on the VST 18 with 25.5 grams of water
• they both tasted the same cold

Are you saying they tasted the same because their paramount extraction percentages are not the same?

I would be personally ecstatic if the VST apologists attacking my posts and studies would publish any sort of study speaking to any of the claims they are making. That would require them to specify precisely and operationally what those claims actually are. I'm particularly looking forward to hearing precisely how the 58.4 mm tamper is better than all other tampers, and seeing the evidence for it.

Until VST or its apologists actually specifies and supplies evidence for their claims, they should stop posting illogical complaints like this one whenever anybody is skeptical about what they say.

I have questions for both sides in this debate:

Scott, isn't it the case that many different compounds are extracted from coffee during the espresso brewing process, and that the specific amount of each compound pulled out of the grounds depends on a host of variables including the coffee species, where it was grown, how it was processed, how it was roasted, the grind setting, the dose, the time water is in contact with the grounds, the water temperature and the water pressure?

And isn't it the case that the specific flavor profile in the cup is going to be a function not only of the total amount of dissolved solids in ratio to the water, i.e., the extraction %, but is also going to depend on the exact amount of each flavor compound that ends up in the dissolved solids?

Finally, isn't it possible to produce different mixtures of the flavor compounds, say by altering a variable like temperature, without drastically changing the weight of the dissolved solids, and therefore the extraction %?

If what I've said is true, then the same, or very close to the same, extraction % reading could result from two different flavor profiles. Therefore, I don't see how extraction % can predict taste in the cup.

I can see how extraction % can tell you whether the cup is grossly underextracted or overextracted, which means the taste will be probably be unpleasant, but that's easy enough to taste. How can extraction % tell you if the coffee is dialed in to the optimum (for you) flavor profile?

Jim, in previous posts you said that the readings weren't stable enough to correlate with taste. But the readings must have fallen within some numeric range. What was it? How close was the range to the magic 18.5%-21%? How much did the readings bounce around in the range? Can you provide us with some numbers?

Peppersass wrote:Jim, in previous posts you said that the readings weren't stable enough to correlate with taste. But the readings must have fallen within some numeric range. What was it? How close was the range to the magic 18.5%-21%? How much did the readings bounce around in the range? Can you provide us with some numbers?

I had a complimentary review version of the Extract Mojo, and ran a preliminary data set for the basic reliability information: test/retest variance, departure from linearity when samples are diluted, and error propagation in the conversions from the raw refractometer readings to TDS levels to Extraction levels. This dataset was exploratory, and not for publication. It was designed to locate the unit's strengths and weaknesses for subsequent documentation. After I requested the additional information I needed to complete the error propagation analysis, Vince asked me to break off the review and return the unit.

I am therefore no expert on the Extract Mojo, and my comments below are addressed to not just it, but to other methods that measure TDS and use this to infer extraction levels as well. For instance, if you bought the calibrated TDS meter from the SCAA, it would have similar problems. My belief is that the combination of measurement errors in TDS, and systematic conversion errors from TDS to extraction, can cause the extraction readings to be roughly +/- 1.5%. This is larger than the entire acceptable range of extraction and nearly as large as the range one actually sees in direct assays.

For instance, the concentration of solubles in the coffee itself goes from about 1% in weaker brewed coffees to about 13% in a ristretto-ish espresso. A 0.1% error in the reading for brewed coffee will give a 10% error in the extraction - taking it from say 19% to about 21%, i.e. the entire acceptable extraction range. The same error in espresso will create much less of a problem; but in espresso, the water weight in the cup is about 60% to 80% of the water that came into contact with the puck and the exact amount may be unknown and vary from shot to shot, dose to dose, and basket to basket (a problem with all percolation methods).

I once did a study of extractions using a mini grinder and the Elektra machine that created a strong linear relation to taste. I was unable to generalize the relation to other grinders and other machines, since each had its own curve. After looking at these data I realized that different grinders had different grind adjustment to extraction ratios, while different machines had different levels of water in the cup/water in contact with the puck levels.

I have no doubt these issues can be addressed in a lab setting, or if extraordinary pains are taken with the measurement. I also have no doubt that if you use one coffee, one grinder and one brewing method, the systematic errors cancel in cup to cup or shot to shot comparisons, so that comparisons can be informative. But I am pessimistic about the measurements made in everyday settings being meaningful in a wider context, across different coffees, roast levels, grinders, and machines.

As a postscript: The review episode has soured the relation between Vince Fedele and me; so it's clear that he doesn't trust me to honestly test the refractometer. However, there are lots of people in the hobbyist community who are perfectly competent to do these tests, and who will do them for free. I look forward to seeing them.

I'm confused by the purpose of the OP, and am addressing the following to Scott:

Whether based on refractometer analysis or something else, what conclusion(s), if any, are we supposed to draw regarding the use of VST/Strada baskets?

Who should?

Who shouldn't?

Why?

BDL

Based on my observations of the postings on this forum and Jim's findings, the people who would benefit most (or would have the least difficulty, depending on which side of the fence you're on), are the ones with a high quality commercial grinder, who weighs every shot and has excellent technique.

Mitch,

Thanks, but you've mistaken me for a sincere pilgrim on the path to knowledge.

My questions were directed to Scott, asking about any practical information contained within the OP itself; and inferentially any other data best be gathered by refractometer relating to tds (and other relevant factoids of brew percentage).

So far what I've gathered from Scott is that VST baskets have "unusually large holes," are grind sensitive, and like doses appropriate to their size. I'm not sure the first is accurate, but it doesn't matter to me much one way or the other; and the second two -- which do matter -- don't come as much of a surprise.

I have positive opinions about the practical use of VST/Strada baskets in my particular set up -- excellent grinder, excellent machine, adequate barista technique purposely adapted to the setup, every shot individually time-measured but not individually weighed, etc. -- and have posted those opinions, their bases, and further speculation, in several H-B threads.

BDL