In the coffee world, crema – the coveted layer of amber foam on a freshly brewed cup of espresso – is hailed as the mark of an excellent espresso, and is much sought after by enthusiasts and baristas.
Essentially an emulsion of carbon dioxide, sugar, and oils, a good crema adds a creamy, aromatic dimension to a smooth, silky shot and elevates the drinking experience. It should linger atop your freshly brewed coffee for a minute or two and have the density to hold the weight of a teaspoon of sugar.
Many coffee fans see the presence of crema as a sign of a quality espresso with a rich, full-bodied flavour profile. But is that always the case?
Variables that Affect Crema Formation
While crema is a strong signifier of the quality of your coffee, there are many variables to account for in its formation.
Sugar and Fat Content
The way beans are processed will ultimately contribute to the density of crema. Natural or dry-processed beans retain more sugar and oils than wet-processed beans.
Darker roasts lose more sugar and fat to the roasting process, causing the consistency of crema to be thinner. In this instance, crema is not a true indicator of the bean’s quality and does not compromise the mouthfeel and flavour profile of the espresso.
The roasting process causes carbon dioxide build-up inside the beans. In the two to 12 days after roasting, the beans undergo a “degassing” process where the gases are released gradually.
This is important because if the beans are brewed during this period of degassing, the escaping carbon dioxide will produce a thick layer of airy crema – but also prevent the full extraction of flavour from the beans.
The resulting espresso will boast a lovely crema top, but a weaker flavour and strong acidic aftertaste.
Finally, highly pressurised portafilters and other technology in coffee brewing machines are designed to aerate the coffee in the brewing process. This can produce a layer of airy foam that mimics the look of crema, but without the sugar, fat and flavour dimension that a true crema holds.
With these factors in play, crema in your espresso should be seen as a bonus, but not a must-have. Before you bemoan the absence of this liquid gold on top of your coffee, have a look at what other qualities a good espresso should possess. After all, coffee is a pleasure – you don’t want to waste your daily allotment on a bad cup.
What Makes a Good Cup of Coffee?
The idea that you can diagnose the quality of your espresso shot based on crema is a long shot (which is also a heavenly way to enjoy your espresso, if we may say so). Here are some other factors you should keep an eye (and nose) out for to spot an excellent espresso.
The ideal water temperature to extract the most flavour from the beans is around 90 to 96 degrees Celsius, allowing the bouquet of smells and flavours to develop fully in the cup.
The cup it is served in should also be heated, so your near-boiling espresso doesn’t suffer “shock” when poured. Cold cups can lower its temperature and prevent the full bloom of flavours.
While you wait for your espresso to cool to drinking temperature, take a minute to appreciate the aroma since this is also another indicator of quality.
While the full bouquet of scents wafting from your cup will vary depending on the blend and bean type, the aroma should be generally full-bodied and fragrant.
There should be no sourness, which indicates under-extraction, or overly harsh, bitter notes – a sign of over-extraction and acidity.
Taste and Mouthfeel
And now, the taste test. The best espresso should be velvety smooth, sliding across your palate with just a hint of bitterness. Too much bitterness or a harsh mouthfeel is a sure sign of over-extraction, where the acids in the coffee have been percolated into the espresso.
Any sour and sharp, salty flavours, on the other hand, will suggest under-extraction caused by over-grinding, or overzealous tamping of the grounds before brewing. The latter causes the hot water to flow unevenly through the “puck” or cake of coffee grounds in the machine, and under-extract the flavours from the beans.
Recall that coffee is comprised of a mixture of fats and sugars, among other compounds. The consistency of a good espresso should show a balance of these.
Swirl the cup gently to check – it should be thick but not syrupy unless you are having an espresso ristretto shot. When you’ve drained your cup, the remaining drops should form a creamy brown residue.
If you have the opportunity to observe the pour, watch the flow. The drizzle of espresso into your cup should begin slow and thick, before slowing to a trickle and then finally drips. If it flows quickly, the water will not stay long enough in the puck to extract its flavours, while a slow flow will produce an espresso that is much too strong, since the hot water is spending too much time getting to know the coffee grounds before percolating.
For best results, the pour, or pull, should take 25 to 30 seconds.
Tips and Tricks
Here are some pointers to ensure your morning pick-me-up turns out just the way you like it.
Fresh, Fine and Even Grounds
For ideal flavour extraction, beans should be freshly ground into a fine, even texture and left to rest for a few seconds before brewing begins. Timing is essential; it ensures that the carbon dioxide has enough time to escape.
Use this grinding size guide to ensure you are neither over-grinding nor under-grinding, as either will affect the fullness, consistency, and taste of your espresso.
At the same time, ensure you grind only the right amount of beans to avoid wastage. When unused grounds are left for too long, oxygen will turn them stale – and no one wants stale coffee.
Tamping the Grounds
After a short rest, the ground coffee is ready to be compacted or “tamped” into the portafilter of the coffee machine. To provide the necessary pressure for infusion, the grounds should form a tightly packed, cake-like layer.
But be sure not to over-tamp – remember that too much compression of the grounds can prevent proper flavour extraction.
The Right Amount of Heat
Your coffee machine should use water between 88 to 96 degrees Celsius for optimum flavour extraction. Anything below 88C produces a weaker shot, while water above 96C will cause over-extraction, leading to a bitter, overly strong espresso.
If you are brewing at home, take care to warm your cup as well. Simply pour a little boiling water into your vessel of choice and let it sit a minute or two before emptying it for the pour.