What is the key to the thickness of coffee grease? What is the reason why the fat in espresso is too thin? Why is the concentrated oil too thick and agglomerated? What are the ingredients of Espresso's oils?

As we all know, the coffee extracted by espresso machines is not only very rich, but also carries a layer of golden oil. Because this layer of oil provides coffee with a rich aroma and dense taste, and is also a unique product of espresso, people often call it the soul of espresso.

But did you know that the role of grease is not only to improve the quality and aroma of coffee, it also contains a lot of information about the coffee/coffee beans themselves. If you are a friend equipped with an espresso machine at home, it should be easy to find that the espresso oil extracted every time is not the same. Sometimes it is rich, sometimes thin, sometimes rough, and sometimes delicate. These are the changes caused by the state of the coffee itself. So what Qianjie wants to share with you today is: how to read the information of the coffee itself through the state of the oil. To a certain level, this is quite helpful to friends who are just getting started. And this is not difficult to do. As long as we understand the principle of change, it will be very simple to interpret ~

First, what we need to know is... First of all, what we need to know is that the oil in espresso is not really oil in the essence. As Front Street often shares, it is a foam group formed by the lipids of coffee beans wrapped in carbon dioxide. Its texture and richness are mainly affected by two aspects: carbon dioxide content and extraction.

When the extraction parameters are the same, what changes the coffee oil is the carbon dioxide content, and the factors affecting the carbon dioxide content are freshness and roasting degree. These are the two main information that we can read from the oil. However, the degree of roasting of coffee beans can be estimated by the color value when we grind them, so the main information we read from the oil is the freshness of the coffee beans. Although we can also know the freshness of the coffee beans from the date printed on the coffee bean bag, the difference between the freshness read from the oil is that we can know in more detail whether the coffee beans have been cured. And when there is a taste problem, we can learn more quickly what the problem is.

Okay, without saying much, let's share with Qianjie what the corresponding oil status of coffee beans with different freshness looks like ~

Rich and rough fat Under the condition that the parameters are normal (the same as the parameters you usually extract), if the espresso you extract carries very rich fat and has a lot of large particle bubbles and agglomerations on the surface. The speed is fast, then it means that the coffee beans you use are very fresh.

Especially when the coffee beans you use are roasted deeper, the fresher they will extract richer and coarser oil. The reason for this is that fresh coffee beans contain a huge amount of carbon dioxide! Qianjie mentioned earlier that the essence of oil is the bubble group formed by the lipids of coffee beans wrapped in carbon dioxide. But when the carbon dioxide content is too high, the oil cannot evenly wrap the carbon dioxide. In this case of more gas and less fat, although there will be a lot of extracted bubbles, they will break very quickly because their stability is not as high.

Usually, the flavor performance of concentrates with this oil will not be very good. When drinking, the flavor is either not obvious enough, or the taste is sparse and the taste is faint. Because too much carbon dioxide will hinder the extraction of flavor substances by hot water, less soluble matter will be extracted with the same parameters. So if we see that the concentrate has such oils and the coffee does not taste so well, it is best to readjust the extraction parameters or put the coffee beans on for a period of time to nourish, so as to ensure that the coffee can be extracted in sufficient quantities.

Thick and delicate oil. If the extracted coffee oil is not as thick as before, but it is not rough, very delicate, very slippery when shaken and reflects light like a mirror, then this high probability means that the beans have entered the taste period.

Because the carbon dioxide in the coffee beans is no longer so much that lipids cannot be evenly wrapped, the bubbles that appear are very stable and delicate. Then at this time, we can easily extract the flavor substances in the coffee, because the amount of carbon dioxide will not hinder the extraction too much. Under the same parameters, the extracted coffee will have richer taste, whether it is flavor or taste, which will be far better than the former.

Fine but thin oil But if under the same parameters, the extracted coffee oil is much thinner than before, then this will mean that the coffee beans are about to/have left the taste period.

Because there is not too much carbon dioxide in the body of the coffee beans to form oil at this time, the extracted oil will be relatively thin. In this state, it will be easier for us to extract soluble substances in coffee than the former, and coffee may taste better. However, it should be noted that since soluble matters are easier to extract, we will more easily dissolve those unlikable substances in coffee, causing negative manifestations such as bitterness, impurities, and astringent in coffee.

At the same time, the appearance of this state of oil also signals that we need to consume coffee beans as soon as possible. Because the existence of carbon dioxide not only hinders extraction and the formation of oil, it also functions to reduce the escape rate of aroma molecules in coffee. When sufficient carbon dioxide is present in coffee, the aroma of coffee that contributes to flavor formation will dissipate much slower. When the carbon dioxide has almost dissipated, the aroma in the coffee will also escape at an accelerated pace. So we'd better consume these beans quickly in a short period of time. Although we may be able to extract a fuller flavor from these beans, their taste period will be very short.

It is worth mentioning that the reason why Qianjie always emphasizes the same extraction parameters is because we need to fix a parameter as the goal when we adjust. For example, Qianjie is debugging the Qianjie classic blending in the bean list every day., the goal will be first set to: 20g of powder will extract 40ml of coffee liquor in 30 seconds. Then first adjust the parameters to this range, and then fine-tune the coffee according to the taste. Secondly, different parameters during extraction can also affect the richness of the oil. To give the simplest example: 20g of powder takes 30 seconds to extract 40ml of coffee oil is more abundant than 20g of powder takes 15 seconds to extract 40ml of concentrated oil. So combining the above two situations, we first need to fix a parameter and then start to compare ~

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