If we exclude the wonderful art of the roaster from the equation – then the recipe for a fine espresso is simply temperature / pressure and time
Temperature 90 degrees +/- 5 degrees
Inlet water pressure 9 bar +/- 2 bar
Percolation time 30 seconds +/- 5 seconds
For 6.5 > 7 g of coffee
Get one of these variables wrong and you will end up with a disappointing result – and one which the espresso, in all its honest virtue, will exhibit to you… through its crema
How and why is complicated… but reflects the mystery that is the perfetto espresso
Espresso is a concentrated solution of salts, sugars, acids (Acetic/ Formic/ Malic /Citric & Lactic) and caffeine
The caffeine content varies according to the relative Arabica/ Robusta content of your chosen espresso recipe… Robusta contains 45% more caffeine than Arabica coffees… and subsequently, also produces a denser beverage and one with more soluble solids…hence why the authentic Italian espresso always contains 10 > 20 % of a good quality Robusta origin
Espresso crema is technically a ‘biphasic system composed of gas globules held within liquid films called lamellae’… these globules are typically in a honeycomb structure… and their persistence is both an important characteristic and a measure of the quality of the espresso produced
Any error in judgement when grinding, brewing/ extraction / temperature is immediately shown in the colour, the texture and the persistence of the espresso crema
If the Crema is light tan coloured / inconsistent and thin (the cream should be c 10% of the total liquor produced) this has resulted from either under extraction …too coarse a grind or an insufficient water temperature
If the Crema is whitish in colour and made up only of big bubbles then the brew has been over extracted and potentially the water temperature is too low
And if the espresso is topped with simply a whitish spot or ring in the middle of the cup and the brew is very black then the temperature has been too high
If the Crema is the correct medium tan / Cadbury milk chocolate type shade – but is simply thin and disappointing…then it may be that your beans are no longer fresh!
It will be ok – but weak and uninspiring…!
The Crema then is the virtue and the sin of a fine espresso…it traps the volatile compounds which make that beautiful aroma… and if not there…we have a beverage which is thin, burnt and without that burst of espresso ‘wowee!’ aroma
The easiest way to make the perfect espresso is with the ESE espresso pod. It really is simplicity personified…. fresh pure espresso each and every time you need it… simply tear open your favourite brew and sit back and make your perfect espresso… then enjoy that espresso moment!