Bad Results, Refractometer Confuses Me

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msg31

#1: Post by msg31 »

I have a Profitec Pro 300, Lagom P64 with SSP High Uniformity Burrs, 18G VST Bakset.

I'm struggling with a bag of La Cabra coffee. It's 2 weeks off roast. Their standard recipe is 17G -> 38G in ~30S. I've tried several variations on that recipe and can't pull a shot that tastes good,

Bought a Coffee-PAL refractometer as a tool to see if I can dial-in espresso faster. I'm using VST's CoffeeTools app to figure out extraction.

Three shots using the La Cabra:

18G Dose -> 45G Yield -> 25 Seconds -> TDS 5.8 -> Extraction 13.9%
18G Dose -> 43G Yield -> 43 Seconds -> TDS 7.1 -> Extraction 17%
18G Dose -> 43G Yield -> 57 Seconds -> TDS 6.3 -> Extraction 15%

None of the shots taste good. The coffee tastes fantastic as a filter (I use a Kalita Wave). But, La Cabra claims their roasts work equally well for espresso and filter.

Confused by the low extractions, I switched to a bag from SoulWork coffee, 7 days off roast.

18G D -> 40G Y -> 24S -> TDS 8.8 -> Extraction 19.6%
18G D -> 42G Y -> 31S -> TDS 8.1 -> Extraction 18.9%

Extractions are getting higher and I'm tasting better flavors in the cup. But, I'm confused how increasing time for this shot lowered extraction. Seems counter-intuitive.

Any thoughts on what's happening with the La Cabra? Can the numbers diagnose anything? It just doesn't taste good.

I will try more with the Soulwork tomorrow, feels like I'm getting close to a nice dialed-in shot. But, again, confused by the counter-intuitive measurement of lower extraction after longer time. What's happening here?

Jeff
Team HB

#2: Post by Jeff »

As far as I've figured out so far, a refractometer alone can't tell you if a cup is good, but it can give you hints as to why one is poor.

In the case of your La Cabra, it's hinting that there is a lot more "goodness" from the beans that could be in your cup. Tim Wendelboe's tips on making espresso [video] suggests that espresso should be at least 20% EY, measured with a filter. Without a filter or centrifuge, I understand that the EY estimates are a little bit higher and have greater variance.

All beans will extract slightly differently even with the same grind and profile. In the case of La Cabra, they recommend at least a 21-day rest for espresso. I don't open mine for a month after roast, some go even longer. I don't know how it behaves so soon after roast.

At a month after roast, I find the grind that I need from my Niche Zero conical to be significantly finer than that of US-based roasters that tend to roast on the light side of things. To get the flavor I enjoy out of La Cabra's coffees, I typically use a moderate length, fill-and-hold preinfusion (~15 seconds total) and a declining-pressure (lever-like) pressure profile for extraction. Pump-on to done timing is often in the 30-45 second range for me. These generally aren't slow shots once they progress into the pressure phase, with extraction rates at the end around 2-3 g/s. My starting ratio for this is around 1:2.5; 17 g in (my machine's "normal" dose), 42 g out.

I don't have a modern flat, so I can't comment on differences that might make.

La Cabra's offerings have definitely been challenging to work with, but always a rewarding experience for me.

jmotzi

#3: Post by jmotzi »

msg31 wrote: ...
18G Dose -> 45G Yield -> 25 Seconds -> TDS 5.8 -> Extraction 13.9%
18G Dose -> 43G Yield -> 43 Seconds -> TDS 7.1 -> Extraction 17%
18G Dose -> 43G Yield -> 57 Seconds -> TDS 6.3 -> Extraction 15%
...
18G D -> 40G Y -> 24S -> TDS 8.8 -> Extraction 19.6%
18G D -> 42G Y -> 31S -> TDS 8.1 -> Extraction 18.9%
...
Extractions are getting higher and I'm tasting better flavors in the cup. But, I'm confused how increasing time for this shot lowered extraction. Seems counter-intuitive...
What are you changing between shots? Your times and yields are both changing every shot with the times quite different considering the smaller changes in yield. Sometimes your time is significantly greater and your yield slightly less - something must be changing. You will likely understand better what you are doing if you shoot for a constant yield. If your shot is 24s one time and 31s the next (and you are using a pump driven machine) then there must be more to the story such as puck preparation, grind, etc.

Yes you are correct that if you keep the grind setting constant, the dose constant and the puck preparation constant, then increased time means in creased yield which means lower TDS (concentration) but higher extraction (total coffee dissolved).

JM
LMWDP #662

msg31

#4: Post by msg31 »

Sorry! Neglected to mention that the variable across these shots is grind adjustment: grinding finer when time increases.

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Peppersass
Supporter ❤

#5: Post by Peppersass »

Several observations:

1. What Jeff is suggesting is that the La Cabra coffee is difficult to extract, which would explain your low %EY readings. Any coffee that has to be rested for a month after roast to get a good extraction is, in my book, hard to extract and likely roasted very light. It may require extreme measures to fully extract (see #5 below.)

2. Refractometer readings can vary a bit, so it's not unusual to see a few tenth of difference between readings, even when measuring the same cup. In addition, there can be slight variations in your measurement protocol, such as how much you stirred the cup before taking the sample, how long you cooled it, etc. (and if you're not cooling the sample -- i.e., equalizing the sample and well temperatures -- then that's another potential source of variation.) And of course, there may be variations in your puck preparation that can shift the readings a bit.

3. There's a lot of disagreement about this, but I'm a proponent of filtering espresso samples. If you're not doing that, your readings will likely be high and could vary.

4. Usually the greatest source of variation is the grinder. If you're using a hopper, the grind can vary depending on how much coffee is in the hopper (weight of beans above the burrs.) If you're single-dosing, there could be variations in retention that you won't catch if you're weighing only the beans going in and not the grounds coming out.

5. Your last post says you're changing the grind when the time increases. Well, that usually increases the extraction yield, but only up to a point. After that, more fines can lengthen the shot time while interfering with extraction. Essentially, grinding finer can reach a point of diminishing returns, which may explain why you saw lower extraction with a longer shot time. That's typically when long, slow pre-infusion becomes the only way to fully extract a light roast.

6. You don't characterize the taste beyond saying it's bad, so it's hard to tell if this is strictly an extraction issue. I would expect that the La Cabra tastes sour because it's under-extracted. Is that the case?
★ Helpful

msg31

#6: Post by msg31 »

@Peppersass:

Yes, pre-dominant flavor of the La Cabra is sour. The measurements are reinforcing to me that, like you and others suggest, I'm under-extracted.

I'm single-dosing. The Lagom P64 has negligible retention. I push a bit of air through the grinder after each dose to remove any remaining fines.

I have a Profitec Pro 300 machine: https://clivecoffee.com/products/profit ... so-machine

It has no concept of pre-infusion - it's full pressure or nothing. Is pre-infusion possible on machines that aren't designed for this?

msg31

#7: Post by msg31 »

3 more data points with the La Cabra

18g D -> 42g Y -> 30s -> 8.7 TDS -> 21% extraction -> Quite sour
17g D -> 42g Y -> 26s -> 8.2 TDS -> 21% extraction -> Less sour
17g D -> 45g Y -> 21s -> 8.1 TDS -> 22% extraction -> Not sour, but no flavor, especially not the sweetness I'm hoping for

The coffee is now 20 days off roast.

I'll try again in a week or so.

platinumlotus

#8: Post by platinumlotus »

21-22% with the Lagom seems to be in the ballpark for deliciousness. For the #3 shot, was it something like hollowness that you tasted-like all the flavors have disappeared from the coffee? If it was the case then you probably grinded fine enough to overextract the coffee.

msg31

#9: Post by msg31 »

I should've mentioned that for each of the above 3 shots I ground coarser to decrease shot time

mathof

#10: Post by mathof »

msg31 wrote:3 more data points with the La Cabra

18g D -> 42g Y -> 30s -> 8.7 TDS -> 21% extraction -> Quite sour
17g D -> 42g Y -> 26s -> 8.2 TDS -> 21% extraction -> Less sour
17g D -> 45g Y -> 21s -> 8.1 TDS -> 22% extraction -> Not sour, but no flavor, especially not the sweetness I'm hoping for

The coffee is now 20 days off roast.

I'll try again in a week or so.
If I were getting extraction yields of 21% and finding the coffee sour, I'd increase the brew water temperature substantially.