How coffee crema is formed, and what it says about your Espresso.
A great cup of coffee without that brownish yellow foam that sits on top of your freshly made shot of espresso to sip from might not look so great after all because a coffee crema could either be a great indication of just how perfect your Espresso is or it could just be an oversell and not meet upto your expectation.
But what is crema and how is it formed?
Crema is formed when espresso is extracted. When air bubbles mix with coffee’s fine-ground soluble oil, it forms a flavoured, aromatic, reddish-brown froth which some people might refer to as the "Guinness effect" because it looks like the top on a pour of the popular beer.
In more details, Crema is made during the extraction process when water and occasional bean oils emulsify. After coffee beans are roasted, they start to release CO2. Most of that's released into the air between roasting and grinding, but whatever CO2 remains within the cells is released during grinding. When hot water hits the dregs with the high of an espresso machine, the water emulsifies the oils within the coffee then gets supersaturated with CO2, leading to many tiny bubbles that structure the foamy layer of crema.
Many barista’s would have various opinions or methods of making their coffee crema, but here are things to keep in mind about your crema.
- If you've got an excessive amount of crema within the cup, you'll have less espresso. Many baristas strive for a crema that's about one-tenth of the espresso.
- Over-extraction, under-extraction, and therefore the coarseness of your grind can all affect crema.
- If your crema lowers after less than a minute, then the extraction was too fast or the coffee roast too light.
- Extraction from a top quality espresso machine should take between 15 and 30 seconds, though this might vary in different machines.
- Remember to let your machine warm up before pulling a shot and ensure the machine is neat regularly to make sure it continues to function properly. A dirty machine could also contribute bitterness to your espresso.
Key factors that affect the crema.
There is a lot happening directly in your espresso demitasse cup. A far better way to understand what affects crema is to figure it backwards: what does the look of the crema tell you about the espresso you're close to drinking? The three main qualities you can observe from your crema are the colour, the thickness or fullness, and the way it lasts.
There are a lot of color variations in cream and not all of them are bad. Colors will vary due to lighter or darker coffee roasts. However, there are other color variations that indicate a problem, such as dark rings around the rim of the mug or cream that is too light.
Exceptionally light creme is a sign that the espresso was improperly extracted. In this case, the cream may also be thinner or not last that long. Insufficient extraction can be the result of a number of issues that occur between grinding, tamping and brewing and simply means that insufficient flavor is coming out of the coffee grounds.
When insufficient extraction is not the problem, the lighter cream can also be the result of a cold espresso machine. Double check to make sure your machine is still at the ideal brewing temperature (195F-205F).
On the other hand, a darker cream is probably the product of excessive extraction, or when too much flavor has been extracted from the coffee grounds. This is also the opposite problem of lighter cream, the problem could be too much pressure when stuffing, or a shot that has been thrown too long. If none of these seem to be the culprit, a very dark cream could also be a sign that the espresso machine is overheated.
Freshly roasted coffee beans will generally produce a more pronounced crema. This is because beans that have recently been roasted still give off some of the oils and gases that begin to emerge after the roasting process. As we have learned, these oils and gases play an important role in creating the foam of the crema in espresso, so you are likely to notice a stronger looking crema in coffee that roasts its own beans.
Another thing that affects the thickness of the cream is the darkness of the bean. Darker roasts generally produce less cream because some oils bleed during packing and mashing. However, lighter roasts are also not ideal for espresso crema. To find espresso roasts made specifically with the right level of oils, search for companies that sell it.
Also, the fullness of the cream varies depending on how the roasted beans have been processed - dry processing is more common and leaves the beans with more natural oils. These oils give a better and fuller cream.
THE DURATION (How long the crema lasts).
If the coffee is too freshly roasted, it still releases too much gas and oils to produce a quality espresso, so the resulting drink will produce a sparkling creme that evaporates quickly. The ideal period for crushing and brewing is 7 to 21 days after roasting. However, this is debatable and we have seen many people advocate for the 12-24 hour rule of letting beans sit for a day or half a day before grinding and preparing them.
If the coffee is freshly roasted, but not too freshly roasted and freshly ground, the crema should last about 2 minutes. Too much or too little extraction can also affect the duration of the crema and will be the first signs that your espresso might not taste the best.
Finally, most new super automatic espresso machines will actually create a "fake" crema that looks like the real thing, but is not actually an emulsion of CO2 and coffee oils. These fake crema won't have the same flavor or complexity as those made with a manual or semi-automatic espresso machine.
What does the crema tell us about the Espresso.
In many ways, the crema give us clues about the Espresso we're about to drink, such as:
- The age of the roast
- The quality of the beans.
- The water temperature and the length of the glass.
All of this information tells us what to expect from espresso, but it doesn't give us the full picture.
Similarly to tasting a new wine or beer for the first time, the crema is a part of the initial taste of the espresso, it gives you the first impression and with that you know what to expect and what not to expect.
ALSO A CREMA DOES NOT DO THIS:
- A BEAUTIFUL CREMA DOES NOT MEAN THAT THE COFFEE WILL TASTE GREAT.
You can roast bad coffee at a dark roast level and get a nice thick, dense crema, and the espresso will always taste bad. The cream can be nice on the eyes, but it's important to focus on balancing the espresso.
And vice-versa, a crema that does not look perfect could still have a great espresso taste. So as gorgeous and beautiful as having a lovely crema could be, in the end as long as you enjoy your cup of coffee, that's all that really truly matters.