Posted Tue Mar 13, 2012, 5:11am Subject: Re: coffee refractometer
Interesting findings, will take me a few days to figure out what's going on.
Question in general: if I take a sample of well-filtered coffee in a sealed syringe with no air, and let it set overnight at room temperature, would anyone expect changes to the concentration of the sample? If so, please post your hypothesis as to changes, direction of change and what you think might be happening.
Example: brew up a cup of coffee, filter it with a gravity filter (very clarified, no fines). Measure the strength with a TDScr per established procedure (cooling in a demitasse or equivalent... etc.) and get a consistent reading of 1.09%.
Draw 5ml samples into 5 syringes, seal, store them in the cupboard, and test them over the next 5 mornings. What do you expect the strengths to be in the subsequent measurements?
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
mitch236 Senior Member Joined: 7 Nov 2003 Posts: 64 Location: Delray Beach Expertise: I love coffee
Espresso: Linea Single Group (PID,... Grinder: Mazzer Robur E
Posted Tue Mar 13, 2012, 7:44am Subject: Re: coffee refractometer
andys Said:
I recently heard a story that is relevant. Bear in mind that I got the story 2nd or 3rd hand, but I have no reason to suspect it's untrue.
A certain former Barista World Champion, known for his excellent coffee roasting, was visiting another former Barista World Champion. The municipal water at the first guy's location is known to be very low in TDS, whereas the second guy's is relatively average. When the first guy tasted his own espresso blend at the second guy's shop, he was shocked, saying, "I've never had my own blend tasting so good!" They looked at a bunch of factors (grinder, espresso machine, etc) but concluded that the water was the reason.
I'm sure the water plays a large part. I will try the Cirqua packets (funny, I saw them but didn't realize I could do the experiment so easily with them!). I am using VST baskets with a Pullman tamper. I'm really hoping it turns out to be my machine since I'm getting a new machine in a few weeks! That would be the easiest solution!
Well, I'd expect it to go down because of precipitation, by crystallization - this is what happens to the reference sugar solution I made up anyway. If you don't get back to the same number after warming up and shaking your syringes, then I would be surprised.
mitch236 Senior Member Joined: 7 Nov 2003 Posts: 64 Location: Delray Beach Expertise: I love coffee
Espresso: Linea Single Group (PID,... Grinder: Mazzer Robur E
Posted Tue Mar 13, 2012, 8:17am Subject: Re: coffee refractometer
This morning as I was playing with the refractometer, I was wondering why one couldn't just drop the filtered solution right from the syringe? Why do we have to filter the coffee into another vessel then transfer the filtered solution with a pipette?
These long range diagnoses are very difficult, but OK, I'll take another stab at it.
What grinder are you using? Grinders make a big difference in extraction yield and extraction evenness. Your various comments (such as difficulty in getting normal extractions, crappy flavor at 19% yield, and lots of fines to deal with) all are consistent with bad grinding.
Bad grinding includes worn burrs in good grinders, good burrs in poorly aligned grinders, good burrs incorrectly mounted, good grinders with bent shafts, and every other unfortunate situation you can think of. So what grinder(s) are you using and when were the burrs changed?
Posted Wed Mar 14, 2012, 5:52am Subject: Re: coffee refractometer
andys Said:
These long range diagnoses are very difficult, but OK, I'll take another stab at it.
What grinder are you using? Grinders make a big difference in extraction yield and extraction evenness. Your various comments (such as difficulty in getting normal extractions, crappy flavor at 19% yield, and lots of fines to deal with) all are consistent with bad grinding.
Bad grinding includes worn burrs in good grinders, good burrs in poorly aligned grinders, good burrs incorrectly mounted, good grinders with bent shafts, and every other unfortunate situation you can think of. So what grinder(s) are you using and when were the burrs changed?
Ditting KR805, two different ones (not personally owned) for some of them. New Bodum Bistro which is most consistent at "pourover" icon setting at about 475 micron. Some were done with my Hario MMS modified, but not any of the dehydration checks.
Keep in mind that the fines are gone when going through a gravity drip filter, too. I understand the extraction things, but in purposefully trying to make an overextraction is just checking the "range" with accepted brew charts.
Theoretically, I should be able to make an overextraction by finer grind in a drip, using long drip time (I can stretch this to >8 minutes by keeping track of the basket fill level and pulse modulating the heater in the BCM-4), and the BCM-4 is pretty good at producing 206°F brew water. By taste, that's overextracted, by brew charts that's overextracted, but TDS never seems to back-calculate to overextracted.
I want to level-set my taste buds to overextracted brew as defined by VSTcr, but still have trouble doing it.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Mar 14, 2012, 5:53am Subject: Re: coffee refractometer
GlennV Said:
Well, I'd expect it to go down because of precipitation, by crystallization - this is what happens to the reference sugar solution I made up anyway. If you don't get back to the same number after warming up and shaking your syringes, then I would be surprised.
I'm still only 3 days into one check and 2 days into another.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
Posted Wed Mar 14, 2012, 9:34am Subject: Re: coffee refractometer
andys Said:
I recently heard a story that is relevant. Bear in mind that I got the story 2nd or 3rd hand, but I have no reason to suspect it's untrue.
A certain former Barista World Champion, known for his excellent coffee roasting, was visiting another former Barista World Champion. The municipal water at the first guy's location is known to be very low in TDS, whereas the second guy's is relatively average. When the first guy tasted his own espresso blend at the second guy's shop, he was shocked, saying, "I've never had my own blend tasting so good!" They looked at a bunch of factors (grinder, espresso machine, etc) but concluded that the water was the reason.
"The impact of water on the coffees blows my mind. Worrying about water isn’t new – brewing coffee with London water pretty much obliterates any interesting or unique flavour characteristics in a coffee. In Copenhagen we were cupping with reverse osmosis treated water (we have similar systems) and in Oslo the water is very soft, and just taste/odour filtered.1
Technically both times the water was within spec – not too hard, not too much TDS. The coffees in Copenhagen were suddenly flat, though we later cupped one at different water TDS quantities and got better results from a slightly higher TDS than the Collective would usually use. This higher TDS would turn out to negatively affect their coffees. In Oslo one coffee noticeably improved (I had worried it was bordering on a touch light in London), others were good and one tasted much worse. I know water effects coffee taste – it was just shocking to be reminded how much of a difference small changes make."
Posted Thu Mar 15, 2012, 5:11am Subject: Re: coffee refractometer
Oh, and just re-tested my water to make sure: it's made of a proprietary mix of distilled and ozonated/filtered well water :-)
9 grains hardness / 3 grains alkalinity.
It has no off odors, no iron, no sulfur. Darn good water if I do say so myself.
------------------------------------------ ----------------------------------------- Le café doit être noir comme le diable, chaud comme l'enfer, pur comme un ange, et doux comme l'amour.
"There is no right answer with coffee. There is only the elixir in your cup at the moment you partake."
"...I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind;..." - Lord Kelvin RECIPES thread => http://www.coffeegeek.com/forums/coffee/machines/585708
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