Three - Taste & Science
Taste & Science
You've read Blog Two 'The Espresso Recipe' and know how to use our Brew Ratios. Blog Three will lay out the procedure we use to write the recipes. If you are not interested in the science, ignore this blog and carry on using your recipe to produce amazing espresso!
Firstly, we are not chemists but merely inquisitive Baristi like you! We have adopted methods laid out by others much brighter than us, if you would like to read even more in depth literature, explore the worlds of Scott Rao, Vince of VST & the creator of the Coffee Brewing Control Chart - Prof Earl E. Lockhart.
Now that the referencing is out the way........
We use a VST Coffee Refractometer (thank you VST for rocking our world!) alongside our taste buds to put a numerical value to the taste of espresso. A refractometer measures the amount we have dissolved as a percentage of the sample, known as 'Total Dissolved Solids' (TDS%). From this we can then calculate the percentage of the DOSE (dry coffee) we have dissolved into the YIELD (espresso). This is known as an Extraction% (EXT%)
EXTRACTION% = YIELD X TDS% / DOSE. (e.g 32g x 10% / 16g = 21.88%)
This Ext% is the value we reference to create the recipe. For an espresso to taste balanced and sweet it will be in the 18%-22% extraction range. Less than this and it starts to taste weak and possibly sour. More than this and it starts to taste very strong and possibly bitter. The human preference to this extraction window was proven with a large experiment in the 50's by Prof Lockhart & again more recently by the SCAA.
With a way to numerically value our taste we start to experiment with each of the ingredients until we have achieved optimum extraction and flavour. This can be difficult to do with taste alone as differences are tiny and with so many tests(sometimes 20-30) our taste buds can start to 'blur'. With DOSE established by the basket size we test YIELD and TIME variants. Once we have maxed out Ext% by adjusting Yield we move onto Time and do the same. (Thank you Matt Perger for this technique)
With coffee being organic & no two berries ever being the same we recommend using our recipe as a starting point and then adjusting the time to taste. We can put you in the ball park but the Barista must hit the home run - sorry for the woeful yank analogy. (yes - I said 'yank').
With all of the ingredients established there are also many other influencing variables. These include; temperature, pressure, flow, water recipe, dose preparation and grinder quality. We wrote our recipes using a traditional machine (9 Bar, 95degrees, Pre-infusion), an affordable grinder (On demand, 64mm Burrs) and Plymouth water (Soft). Please note that if your water, equipment and technique vary from ours the recipe should be used as a starting point and then adjusted to taste.
For example, it is possible to achieve high EXT% in shorter YIELDS if you use an expensive high quality grinder with large blades, we chose to write our recipes with longer YIELDS as this makes it easier to produce high EXT% with most grinders of a reasonable quality.
Ok, enough of that. In Blog Three we will be back to good old Barista-ing!!