Over/Under extraction

oldboybewer

After many years brewing coffee and searching the net for more info, I've finally found how to brew coffee my way that I really enjoy.  I've broken all the standard ideas and rules, especially after seeing what Matt Perger & Scott Rao said about "over extraction".  They basically argued that there is no such thing as over extraction.  I thought about this for a long time and realized that if one was to brew a batch of "cold Brew" which requires at least 18-24 hours of brew time,  Time must not be a factor in over extraction.  It must be temperature related.

I have an electric kettle that will offer 96C which is a good temperature start for the extraction.  I also use a stainless steel Bodum "type" unit that has a double thermal wall to maintain temperature.  I pour hot tap water into this Bodum and when the water is ready, I pour this out and add the coffee.  I then pour approximately half of the water, stir to soak and then pour in the rest.  I insert the plunger  but not into the coffee grinds to help maintain heat.  After 2 minutes, I remove the plunger and gently stir the bloom to allow it to sink.  I replace the plunger at the top.  After 9-10 minutes, I again remove the plunger and scoop out the floating foam and other material with a large spoon.  I then slowly plunge to the bottom.

The coffee is sweet with a lot of quality notes. There is no over extraction nor under extraction.  In fact, I found that any bitter or sour notes comes from not enough brew time (Under extraction).  The coffee can be finely ground rather than the standard Bodum coarseness.  Too coarse and the brew time has to be extended.  However, a longer brew time will only work if the temperature is maintained.  Temperatures above 96C will extract unwanted flavours and this, is what I believe to be the most common reason for over extraction.  I welcome any input on this idea. 

   

admin

on 1572018274:

After many years brewing coffee and searching the net for more info, I've finally found how to brew coffee my way that I really enjoy.  I've broken all the standard ideas and rules, especially after seeing what Matt Perger & Scott Rao said about "over extraction".  They basically argued that there is no such thing as over extraction.  I thought about this for a long time and realized that if one was to brew a batch of "cold Brew" which requires at least 18-24 hours of brew time,  Time must not be a factor in over extraction.  It must be temperature related. I have an electric kettle that will offer 96C which is a good temperature start for the extraction.  I also use a stainless steel Bodum "type" unit that has a double thermal wall to maintain temperature.  I pour hot tap water into this Bodum and when the water is ready, I pour this out and add the coffee.  I then pour approximately half of the water, stir to soak and then pour in the rest.  I insert the plunger  but not into the coffee grinds to help maintain heat.  After 2 minutes, I remove the plunger and gently stir the bloom to allow it to sink.  I replace the plunger at the top.  After 9-10 minutes, I again remove the plunger and scoop out the floating foam and other material with a large spoon.  I then slowly plunge to the bottom. The coffee is sweet with a lot of quality notes. There is no over extraction nor under extraction.  In fact, I found that any bitter or sour notes comes from not enough brew time (Under extraction).  The coffee can be finely ground rather than the standard Bodum coarseness.  Too coarse and the brew time has to be extended.  However, a longer brew time will only work if the temperature is maintained.  Temperatures above 96C will extract unwanted flavours and this, is what I believe to be the most common reason for over extraction.  I welcome any input on this idea. 

wow, an interesting one OBB - I guess there are a number of common 'truths' we just take for granted - one of the key ones being that you get the best of the extraction in the first 25-30secs (with espresso, at least); interesting to see what comments come on this temp-related question (rather than time-related)!

Simon

Yeah it is a fascinating topic... one that I've pondered many a time! To me the temperature is the catalyst for the rate of extraction. Hence why cold brew takes so long. Am not sure if I understand that about over extraction not being possible... unless they're referring to not being able to extract more than is literally in there, which is a no brainer haha, of course you can't. But there becomes a point in which you can extract all the good stuff, and then if you keep it going too long end up extracting compounds you don't necessarily want in your cup. But what I'm wondering is, does temperature affect the QUALITY of extraction (or only the speed at which it occurs)? As we know cold brew has different taste qualities and emphases to other brewing methods. Just some ponderings to throw into the mix... Is there some other factor that is affected through different temperatures used, or solely the speed at which extraction occurs (this isn't taking into account channelling etc)?

DrD

If you want to get a bit "sciencey", there is an extract of an article on how brew water temperature affects extraction characteristics, specifically for espresso unfortunately. Interesting reading nonetheless ... https://www.beanscenemag.com.au/brew-water-temperature-effect-espresso-extraction/

askthecoffeeguy

I would say that over extraction is definitely possible through a coffee machine because if you run too much water through the coffee your are going to be pulling out bitter and burnt 'notes' that dont taste good. And for filter coffee I think this also comes into play, the brew ratio's and brew time needs to be just right - leave the coffee in contact with the water for too long and it will definitely taste 'too strong' and it loses its individual character and just tastes like 'strong coffee' which I dont enjoy (depending upon how much coffee you are using to start off with I guess) I too like to keep my water temperature down for plunger or brewed coffee for a sweeter taste with less bitter notes - somewhere between 82 to 86C seems to be where I hit my 'sweet spot' Pat

K_Bean_Coffee

That’s a very interesting read. Thanks for posting the link.