Matt Perger - Reddit AMA brewing discussion - Page 3

#21: Post by **IMAWriter** » May 20th, 2015, 11:37 pm

I have, for several years been doing Hario V60 and Kalita with boiling (heavily roiling) water when preparing 2 cups, a bit lower, 206f when doing one cup...really a mug...about 8oz.
As always, it depends a lot on coffee, but as I only do SO's in the manual pour mode, they are usually city +, well short of 2nd crack, or even lighter.
I found I do not like things so hot in my vac pot brews. Just taste preference, I guess. It's quite easy to tell how quickly the temperature drops in a glass vessel, so while the first 30 seconds is for the bloom, I reheat the pouring water to get back to a boil, then continue. I taste no overt over-extraction. The only time I had that so of thing was just a measurement error of coffee to water ratio.

May 21st, 2015, 1:21 am

NoStream wrote:I'm not sure what exactly you're getting at here. Coffee has some, mild bitterness to it, but coffee can be roasted and brewed as to have minimal bitterness. That's not really the point since presumably we want to keep bitterness to a minimum.

My point was that although over extraction almost always causes bitterness, bitterness needn't necessarily indicate over extraction. That is, overextracted bitterness is one type of bitterness. Which it seems like you agree with. I'm a bit confused...

Coffee is a balance of many flavors, bitter being one of the taste components sought (more so in the case of folks like Southern Italians). Sugars and acids dissolve quicker and more easily, so we're in complete agreement that it (bitterness) is mostly exaggerated in cases of over-extraction. But that doesn't mean that there isn't an abundance of pleasant bitter tasting compounds in coffee to begin with, even properly extracted to target sweetness and acidity. It's also a result of the amino acids and reduced sugars participating in the Maillard reaction, and hence, present in any roasted coffee (more so in robusta, but we're not focusing on that species specifically).

Chlorogenic acids contribute to bitterness perceived in coffee, both via the above mentioned Maillard reaction and Strecker's degradation. Bitterness increases during roasting due to the release of caffeic acid and other phenols that make up the numerous flavor compounds in the cup. More info available here if you have access to scientific articles

More clearly stated here:
Source: Ginz M; Enhelhardt UH (1995) Analysis of Bitter fractions of Roasted Coffee by LC-ESI_MS- New Chlorogenic acid derivatives. In: Proc. 16th Int. Sci. Coll. Coffee (Kyoto) ASIC, Paris.

#23: Post by **NoStream** » May 21st, 2015, 3:09 am

TomC wrote: Coffee is a balance of many flavors, bitter being one of the taste components sought (more so in the case of folks like Southern Italians). Sugars and acids dissolve quicker and more easily, so we're in complete agreement that it (bitterness) is mostly exaggerated in cases of over-extraction. But that doesn't mean that there isn't an abundance of pleasant bitter tasting compounds in coffee to begin with, even properly extracted to target sweetness and acidity. It's also a result of the amino acids and reduced sugars participating in the Maillard reaction, and hence, present in any roasted coffee (more so in robusta, but we're not focusing on that species specifically).

Chlorogenic acids contribute to bitterness perceived in coffee, both via the above mentioned Maillard reaction and Strecker's degradation. Bitterness increases during roasting due to the release of caffeic acid and other phenols that make up the numerous flavor compounds in the cup. More info available here if you have access to scientific articles

If someone were to enjoy bitterness - and I know that's a thing with regards to coffee - then all the more reason to use some really hot water. It's funny, after talking to so many third-wavers, the idea of enjoying bitterness is a bit alien even though a slight bitterness in coffee doesn't really bother me.

I'm aware of bitterness increasing during the roast. My understanding was that this is largely related to quinic acid. I'll look into the link.

There's also some loss of bitterness in the roast, due to CGA degradation - as you mentioned. So bitterness doesn't correspond to roast level or roast duration in any sort of linear fashion. Once you get part-way through first crack, though, bitterness only increases with additional roast, through those processes you mentioned.

May 21st, 2015, 11:07 am

NoStream wrote:. So bitterness doesn't correspond to roast level or roast duration in any sort of linear fashion. Once you get part-way through first crack, though, bitterness only increases with additional roast, through those processes you mentioned.

I'm not following your statement above, the appear to contradict each other.

Here's a great article on taste perception in general. http://www.tastingscience.info/publicat ... ctions.pdf

Paul Songer has a great deal of info on the topic as well. I wish his presentation in Oslo in 2010 for the NBC was easily found.

Paul Songer wrote:However, roasting time also has an effect in the sweetness to astringency continuum and this depends on the innate green bean quality. The body will be emphasized in a sweeter coffee and perceived differently in an astringent coffee. As the sugar browning deepens, sweetness is sacrificed to aromatics (through carmelization, Maillard reactions, and Strecker degradations). Roasting affects levels of astringency in terms of chlorogenic acid breakdown (darker, more astringent phenols balanced by more quinic acid, but other astringent aspects are lessened through roasting). Other considerations are how sensory attention is drawn (more acidic coffees are usually rated as having lower body) and how the brewed solution of coffee evolves over time. Bitterness can also play a role, so the degradation of chlorogenic acids (which by themselves are usually bitter and sometimes astringent) that have astringent phenols and various acids (most notably quinic, which is sour/bitter) as their degradation by products.

Paul Songer wrote:The chemical aspects of astringency and carbohydrates (and sometimes bitterness) add to or subtract from this basic experience, not always in predictable ways. From a roasting perspective, these aspects can be maximized or minimized, but much depends on the initial chemical aspects of the bean. At darker roasts, chlorogenic acids degenerate into quinic and other acids and (astringent) phenols. The darker the roast, the more degradation of sucrose occurs (but at the same time, more cell wall material becomes soluble).

#25: Post by **NoStream** » May 21st, 2015, 12:06 pm

TomC wrote:I'm not following your statement above, the appear to contradict each other.

CGA degradation reduces bitterness. Quinic acid generation and other processes increase bitterness. At some point during or near the end of first crack, bitterness reaches its minimum as CGA degradation slows down and quinic acid generation and other "roasty tasting" processes continue or speed up. If we imagine bitterness as a curve graphed versus time, it first decrease and then increases. Or at least that's the argument in Hoos' book - and one that I've found to be correct. My point is just that the simple view of lighter = less bitter isn't quite true, something that even Wendelboe has mentioned when talking about development time. (You need enough time for CGA degradation.)

Thanks for the info, also.

May 21st, 2015, 1:07 pm

NoStream wrote:CGA degradation reduces bitterness. Quinic acid generation and other processes increase bitterness. At some point during or near the end of first crack, bitterness reaches its minimum as CGA degradation slows down and quinic acid generation and other "roasty tasting" processes continue or speed up. If we imagine bitterness as a curve graphed versus time, it first decrease and then increases. Or at least that's the argument in Hoos' book - and one that I've found to be correct. My point is just that the simple view of lighter = less bitter isn't quite true, something that even Wendelboe has mentioned when talking about development time. (You need enough time for CGA degradation.)

Thanks for the info, also.

we're mostly on the same page. This is the only part I was emphasizing. But my contention is that the majority of the coffee drinking public (outside of say, a Moroccan coffee service where it's roasted ultra light to a mustard yellow color, or sometimes done with Yemen coffee mixed with spices) for the most part, are drinking roasts that are never going to be so short as to even encounter latent bitterness from high CGA content. They're going to be drinking roasts that vary from first crack, onward. And from that point on, there is a gradual increase in bitterness. That's an inescapable fact documented in nearly all coffee literature.

#27: Post by **jyounk** » May 24th, 2015, 12:43 pm

Intriguing thoughts. I will apply this to the wave tomorrow morning

#28: Post by **Bluecold** » May 26th, 2015, 10:08 am

Bluecold wrote:I measured it with a PT100 sensor, which was single-point calibrated at boiling tap water at about 2m above sea level being assumed to be 100 deg C. This sensor measured at the bottom part of the extraction bed.
I think it would make sense to assume rough linearity in the neighborhood of the 100C. I'll report back.

Slurry temperature when starting with a kettle full of 93c water, making half a litre (yield) of coffee from a ceramic Kalita Wave 185 using 35 grams of coffee. The probe tip was placed at the eyeballed middle center of the dry coffee bed. The filter was rinsed with hot water quite a while before the coffee was made so the Wave can be considered to have been at room temperature. The starting kettle temperature and the slurry were measured using the same sensor.

time		temperature 
(min:s)   (deg C)
 0.30		55 (end of bloom) 
 1.00		85
 1.30		86
 2.00		86
 2.30		86 (drawdown starts)
 3.00		86
 3.30		86 (coffee is done, after this, 50ml of coffee comes out of the brewer)
 4.00		85 
 5.30		84
 10.00	  74

So in this case I had a 6 degree drop, but this was half a litre and I don't remember the previous measurement.
In any case, a ceramic filter holder full of wet coffee grounds insulates quite well! In 5 minutes, it only lost 10 degree C. Much less than I'd expect. I'm impressed.