So yesterday I ground up my coffee, I ground it to extract 60ml espresso over 20 seconds. There might be a more technical way of phrasing that, but until I discover it I will use that.
As expected from the appearance there were a few beans which had been over roasted, whilst it was drinkable, it was very bitter, had I bought it from a cafe I'd have been disappointed.
I was desperate to find a reason that perhaps it wasn't just my roast, I re-checked the grinder and all was fine, I pulled another shot, same taste, so I admitted defeat. I was able to comfort myself with the fact it was my first roast, and I think in the circumstances (no proper equipment, experience or mentoring) I'd done alright. I know, I know, a bad workman always blames his saucepans..
So I journeyed online to educate myself further on what causes and how you can prevent bitter tasting coffee. Here's what I found..
Up until recently there hadn't been much research done into what makes coffee bitter, but as peoples passion for the drink has grown and coffee is more popular than ever around the globe people have taken interest, they want to know everything there is to know about this wonderful common man's gold.
Dr Thomas Hofmann, from the Technical University of Munich has a PhD in food chemistry and molecular sensory science and I imagine Heston Blumenthal's mobile number. In his initial lab research he found that caffeine, often considered the guilty chemical, only makes up for 15% of the coffee's bitterness, noting that levels of the bitter tasting chemicals were just as high in decaffeinated brews.
He puts the bitterness down to the roasting and extraction; he trained a panel of tasters to taste and put in order levels of bitterness, through this panels work they have been able to deduce that the longer a coffee is roasted for the harsher the taste shall be, roasting a bean into the second crack will produce in coffee well suited for espresso but also much more likely to be bitter.
There are two compounds that he puts this bitter taste down to; Chlorogenic Acid Lactones (CAL) and Phenylindanes (PHL). Neither of which can be found in unroasted green beans. CAL is made up of 10 chemicals which can be found in Light - Medium roasts. PHL is found in Dark espresso roasts, it is this compound that when added to the CAL compounds produced the harsher taste.
He goes on however to say the extraction will also have a large impact on the taste, I don't think we need PhDs in food chemistry to say that an espresso machine will produce a fuller flavour and to some a more bitter coffee than a french press or a filter. He does explain though that this is due to the fact that both the CAL and PHL are extremely heat sensitive, and so the high heat levels of an espresso group and the pressure emphasise the flavour of these bitter compounds.
His research now is extending to if it is possible through alternative harvest or washing methods you can reduce the presence of these chemicals later in the process. I wish him luck with his work, however hope he never does find an answer. This battle between the natural occurring chemicals and the roasters and baristas is what drives me to be in this business.
Finding the perfect balance between roast time, temperature, grind density and extraction is the art of our work.
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