This is a multi-part message in MIME format. I was curious as to thoughts on why different non-pressure extraction methods have various times. Hario Vac Pot instructions have the water and coffee grounds infusing for 45 seconds Cona C instructions are similar: 45 seconds to 2 minutes French press (from the SM web site) recommend 2.5-3 minutes "Cupping" has the water and grounds infusing for 3 minutes. Wouldn't one think thing that the coffee grounds should "soak" for about the same total of time (3 minutes) for all methods?
--- "B. Scott Harroff" wrote: <Snip> My Bodum evac holds the water up with the grounds for almost 2 minutes, and it's the turbulance that makes for a complete extraction, as well as the forcefull sucking of the water through the grounds going back down. Shaking a presspot for two minutes would probably shorten extraction time for that method. Charlie Oaxaca dreamin' Yahoo! DSL – Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com
B. Scott Harroff wrote: I was curious as to thoughts on why different non-pressure extraction methods have various times. Wouldn't one think thing that the coffee grounds should "soak" for about the same total of time (3 minutes) for all methods? Scott, One thing that you need to remember about the different brewing methods are that the total contact time (water & coffee together, prior to filtration) has an overall effect on the final cup. A vacpot that drains slow, say 1.5minutes would need an infusion time of an additional 1.5 minutes for a total contact time of 3 minutes. I adjust my total contact time to 4 minutes, as I prefer that level of extraction. You can affect the drawback rate in a vacpot by adjusting the grind level, and you will also need to time that new level, and account for it, when you brew your next pot. Another reference is: www.coffeechemestry.com quote: *Correct grind/time ratio* Once a brew ratio from the chart has been selected, simply adjust the grind either coarser/finer so the infusion falls within the "optimum" box. Bear i= n mind that since underirable copounds are extracted later in the brewing cycle, the entire brewing time should not exceed 4 to 6 minutes. Extraction over the 6 min limit results in a beverage with a high concentration of phenolic (bitter) compounds as seen in over-extracted beverages. Gary
Bad link, try here:http://coffeechemistry.com/quality/brewing.htmGary
B. Scott Harroff wrote: [snip] <Snip> On the Vac Pots, when they talk about extraction time, they are usually referring to the time it all rises and gets to the top and the bubbles start coming as the beginning. Then the end is marked by the stop of this time and the beginning of its descent. However, the real extraction time starts when the water is hot enough and comes in contact with the grinds as it begins its upward rise. Likewise, it is still extracting as it goes down. Of course, you are dealing with a bell curve on the extraction, so that at first only a small part of the water is hitting the grinds and it goes up from there. Then that is reversed. I think I figured out one time that if you wanted an extraction time of around 4 minutes in a vac pot, if you take the full time the water is making contact with the grinds and factor in the amount of water making contact through the whole process, you would need a total time from first beginnings of water rising till the last sinks through the hole to be around 7 minutes. Assuming you have an "extraction" time of 1 minute (just to make it easy), that means you have 2 minutes left. If you assuming a consistent rise and drop rate (which isn't going to probably happen exactly, especially on the downward drop) you could say that half the water will only be in contact with half the grinds for half the time. So, that means you double the time rate to get an approximate full extraction equivalent to normal. That means the up and down time needs a total of 4 minutes to process to equal 2 minutes at full extraction mode. So, you then have 5 minutes extraction time total to equal 3 minutes in a press pot. I think I came up with 7 because I was basing it on a 4 minute extraction time. Note: this is a very "rough" estimate, assuming the rise and fall are at equal rates and consistent, which they are not going to be. One happens faster than the other and the rates of ascent and decent vary at different stages. Also, the first water that comes out is not all that hot. I know because I put my finger in it once and it was cold still. When I was attempting to get my drop time down in figuring out grind size and all that with the Cory glass rod, I came up with that as at least something to shoot for as a total time. It seemed to work. You can have a 45 second "extraction" time in the vac, but it does you no good if your drop rate takes 8 minutes and your rise rate is 3, that is a total of almost 12 minutes. Back in using my formula, that equates to an extraction time of 6.5 minutes in the press pot. Also, I know that you don't get better coffee by increasing the extraction time. IOW, you can't use half as much coffee and double the time of extraction and expect to get coffee that doesn't taste over extracted. The fact is, however, that half the water in the up and down periods of the vac pot cycle will be in contact with the grinds and be extracting longer than the other half of the water that has left or has yet to rise. It was just to get an estimate. :-) -- Rick Copple Marble Falls, TX
Alchemist John did a GREAT discussion/comparison of coffee-making mathods to laboratory chemical reactions several months ago. Its good that we have so many smart people on the list--I've learned an awful lot. Seems to me that grind and contact time and temp and agitation and a few other things could play into this as far as the optimum time for extraction for any given method. Not to mention roast and origin and age and water hardness and ???? Might be an interesting experiment for somebody with an interest and lots of spare time. Also it's likely to produce attribute data so you'll need a lot of trials and a tasting panel for best results. I, for one, would be most interested in the results! Dean Oaxaca Charlie wrote: <Snip>