Between the Cracks
All the action in coffee roasting happens between the cracks, that is, between the two points during the roast where coffee beans expand rapidly with an audible ‘crack’. The expansion is caused by the release of CO2 gas and steam. Prior to reaching ‘first crack’ the bean is dense and undeveloped. It is something vegetable, not coffee as we know it, and a drink made from it would likely be unpleasant. Green beans have a distinctive scent, slightly sour and not particularly appetising, but it is the scent that greets me when I open up the roastery in the morning before coffee roasting gets going.
In any roast a few beans will expand before the others, usually when their temperature is heading towards 200°C, with the rest following soon after. Immediately after first crack our senses confirm we definitely have coffee of some description. At this point we have a `city roast’ which will highlight both the strengths and weaknesses of our beans. Acidity and sweetness will be at their highest and some bitter alkaloids are untransformed. Browning reactions will have just got started so the beans can look patchy and blotchy rather than a nice even colour. None the less, really good coffees can shine with a very light roast and will be at their most flavoursome, with any fruit or floral characters at their strongest. While enthusiasts will most appreciate such a light roast, acidity can mask some of the underlying sweetness and the coffee may seem a little thin. Some lightly roasted coffees will challenge the palates of those who are not accustomed to them, especially if the espresso machine temperature is set too low and delivers a sour shot, but many coffee-lovers will trace their growing appreciation as a journey towards lighter roasts and finer beans.
Given just a few extra minutes of roasting we are reaching the other end of the roast window, with the bean probe now registering around 230°C. Just prior to the ‘second crack’ we achieve a `full city plus roast’, or `Viennese’ or ‘light French’ if we wait a fraction longer and allow second crack to start. Full city plus is as far as we would normally ever take a roast with high-quality beans. At this point the coffee has changed considerably. The colour is usually a nice even brown and the beans may glisten with natural oils. The beans look cleaner as they have shed any clinging chaff or residual parchment.
Although visually satisfying, most of those fruit or floral notes have gone or are more muted. Acidity, which gives a liveliness or `brightness’ to the flavour, has dropped as has some of the bitterness due to alkaloids. This is replaced by bitterness from caramelisation of sugar, so overall sweetness is reduced although some might perceive more sweetness due to the lestened acidity. The coffee can seem thicker due to more soluble material being formed and dissolved. A few good coffees may do quite well up to a Viennese roast and some lesser coffees are drinkable with a flavour profile that is familiar to most coffee drinkers. Cheap dark-roasted coffee, often unkindly labelled ‘Italian roast’, tastes generically of `coffee’ with bitter and charred notes. Unfortunately many believe this is how coffee should be.
The sweet spot lies somewhere between the cracks. Exactly where depends on the coffee and individual preferences, which is why we like to work directly with our customers to tune the roast to their liking. We feel that fine coffee is at its best when it is unblended and so prefer to develop a `house roast’ rather than a `house blend’. We also like the quality of the coffee to speak for itself.
If your coffee philosophy gels with ours, why not give us a call?