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Extraction Yield for pour-over methods

PostPosted: Tue Apr 29, 2014 11:34 am
I'm trying to establish a correct formula for calculating the extraction yield (EXT) for pour-over methods of coffee preparation as I don't have enough money to buy VST refractometer and don't like to spend money on their software either (their patent claims aimed at netphilosopher on coffeegeek made me more than angry).
I live in Europe (and this server is located in the UK AFAIK) so these patents can not have any effect on us at all, however if doubt please move this whole post to the members-only area.

Currently I think I have nailed some "basic" stuff - I can calculate EXT from known value of TDS (obtained by drying a 50 g sample of the beverage and weighing it on 0,01 g scale) Dose and Beverage Weight.

Now it's time to gather enough test data and try to obtain correct approximate formula including side effects such as CO2 and Moisture content in Dose.

The equations accounting for Brew Water and Liquid Retained Ratio seems bit overcomplicated (actual measurements show values of 2,3-2,4 for LRR) and not so precise as exact measurement of just the Beverage weight so I will ignore that matter for now.

please see the attached image, but in any case:


RE: Extraction Yield for pour-over methods

PostPosted: Tue Apr 29, 2014 12:00 pm
by dr.chris
So far so good :) You might also want to think about dissolved solids already present in the water used for brewing.

I'd like to think that I might be able to help, given that I used to do academic work on modelling mineral extraction through leaching, but its not always easy to translate knowledge from one process to another however similar they may be.

PostPosted: Tue Apr 29, 2014 12:42 pm
According to SCAA:
Recommended TDS: 150 ppm
Acceptable TDS: 75-250 ppm
150 ppm is 0,0150 %. So correction is possible and simple however I think it can be totally omitted (it's 100 times smaller value)

EXT = ( TDS% - water_tds ) * DOSE / BEV

PostPosted: Tue Apr 29, 2014 12:50 pm
But hey - this very closely looks like VST's correction for TDS. Now it makes a sense! Thanks a lot, dr.chris!