As we all know, the espresso extracted by an espresso machine is not only very rich and concentrated, but also comes with a layer of golden crema. Because this layer of crema gives the coffee a rich aroma and a dense mouthfeel, and is also a unique product of espresso, people often call it the soul of espresso.But did you know? The role of crema is not just to improve the quality and aroma of coffee; it also contains a lot of information about the coffee/coffee beans themselves. If you have an espresso machine at home, it should not be hard to notice that the crema extracted each time is not always the same—sometimes thick, sometimes thin, sometimes rough, sometimes fine. These changes are caused by the state of the coffee itself.So today Front Street would like to share with you: how to read information about the coffee itself through the state of the crema. In a way, this is quite helpful for beginners. And it is not difficult to do—as long as we understand the principles behind the changes, interpreting it becomes very simple~First, what we need to know is...First, what we need to know is that this layer of crema on espresso is not actually oil in the true sense. As Front Street often shares, it is a foam composed of coffee bean lipids wrapping around carbon dioxide. Its texture and thickness are mainly affected by two aspects: the carbon dioxide content and the extraction.When the extraction parameters are the same, what changes the crema is the carbon dioxide content, and the factors affecting the carbon dioxide content are freshness and roast level. These are the two main pieces of information we can read from the crema. But the roast level of the coffee beans can already be roughly inferred from the color value when we grind the beans, so the main information we read from the crema is—the freshness of the coffee beans.Although we can also learn the freshness of the coffee beans from the date printed on the coffee bag, the difference in reading freshness from the crema is that we can know in more detail whether the beans have been rested properly. And when there are flavor problems, we can more quickly find out where the problem lies.Alright, without further ado, next let Front Street share what the crema states generally look like for coffee beans of different freshness~Under normal parameters(not much different from your usual extraction parameters), if the espresso you extract carries a very thick crema, with many large bubbles on the surface and a very fast collapsing speed, then it means the coffee beans you are using are very fresh.Especially when the coffee beans you use are darker roasted, the fresher they are, the thicker and rougher the crema extracted will be. The reason for this situation is that fresh coffee beans contain a huge amount of carbon dioxide!As Front Street mentioned earlier, the essence of crema is a foam composed of coffee bean lipids wrapping around carbon dioxide. But when the carbon dioxide content is too high, the lipids cannot evenly wrap all of the carbon dioxide. In this situation of more gas and less lipids, although many bubbles will be extracted, they will break very quickly because their stability is not high enough.Usually, espresso with this kind of crema will not perform very well in flavor. It either tastes not obvious enough in flavor, or feels thin in mouthfeel and weak in taste. This is because too much carbon dioxide hinders the extraction of flavor substances by hot water, so fewer soluble substances are extracted under the same parameters.So if we see espresso with this kind of crema and the coffee does not taste particularly outstanding, then it is best to readjust the extraction parameters or let the coffee beans rest for a period of time. Only in this way can we ensure that the deliciousness of the coffee can be extracted in sufficient amount.And if the extracted crema is not as thick as before, but is not rough and is very fine, shakes very smoothly, and can reflect light like a mirror, then this most likely means the beans have entered thepeak flavor period.This is because at this time the carbon dioxide inside the coffee beans is no longer so abundant that the lipids cannot wrap it evenly, so the bubbles presented are very stable and very fine. At this point, we can easily extract the flavor substances in the coffee, because the amount of carbon dioxide will no longer excessively hinder extraction. Under the same parameters, the extracted coffee will have richer deliciousness, and both flavor and mouthfeel will be far better than the former.But if, under the same parameters, the extracted crema is much thinner than before, then this means the coffee beans are about to leave or have already left the peak flavor period.This is because at this time there is no longer too much carbon dioxide inside the coffee beans to form crema, so the extracted crema will be relatively thin.In this state, we will extract soluble substances from the coffee more easily than in the former case, and the coffee may taste even better. But note that because soluble substances are easier to extract, we are also more likely to dissolve those unpleasant substances in the coffee, causing negative performances such as bitterness, muddiness, and astringency.At the same time, the appearance of this kind of crema also signals that we need to consume the coffee beans as soon as possible. This is because carbon dioxide not only hinders extraction and forms crema, but also has the function of slowing down the escape rate of aroma molecules in coffee.When there is sufficient carbon dioxide in the coffee, the coffee aromas that contribute to flavor formation escape much more slowly. And when the carbon dioxide has mostly dissipated, the aromas in the coffee will also escape faster. So we had best consume these beans quickly in a short period of time. Although we may be able to extract fuller flavors from these beans, their peak flavor period will be very short.It is worth mentioning thatthe reason Front Street keeps emphasizing under the same extraction parameters is that we need to fix one parameter as our target when adjusting. For example, when Front Street debugs theFront Street Classic Blendon the daily bean list, we first set the target at: 20g of powder extracting 40ml of coffee liquid in 30 seconds. Then first adjust the parameters into this range, and then fine-tune the coffee according to taste.Second, different extraction parameters will also affect the thickness of the crema. To give the simplest example: 20g of powder extracting 40ml in 30 seconds will produce a thicker crema than 20g of powder extracting 40ml in 15 seconds. So considering the above two situations, we first need to fix one parameter, and then begin comparing~
The above content is compiled by CoffeeHunters, a coffee news website.
