As we all know, the coffee extracted by an espresso machine is not only very rich, but also has a layer of golden oil. And because this layer of oil will provide the coffee with a fragrant aroma and dense taste, and is also a unique product of espresso, people often call it the soul of espresso.But do you know that the role of oil is not only to enhance the quality and flavor of coffee, but also to contain a lot of information about the coffee/coffee beans themselves. If you have an espresso machine at home, it will be easy to find that the espresso oil extracted every time is not always 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 Front Street wants to share with you today is: how to read the information of the coffee itself through the state of the oil. In a way, 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 is very simple to interpret~First, what we need to know is...First of all, what we need to know is that the layer of oil in espresso is not really oil in nature. As we often share on the front street, it is a foam group formed by carbon dioxide wrapped in the lipids of coffee beans. 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 that affect the carbon dioxide content are freshness and roasting degree. These are the two main pieces of information we can read from the oil. However, the roasting degree of coffee beans can be roughly estimated based on the color value when we grind the powder, so the main information we read in 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 in the freshness read from the oil is that we can know in more detail whether the coffee beans are healthy or not. And when there is a taste problem, we can know more quickly where the problem is.Okay, without further ado, let Front Street share what the corresponding oil states of coffee beans with different degrees of freshness look like~When the parameters are normal(Same as your usual extraction parameters), if the espresso you extract carries very rich oils, has a lot of large bubbles on the surface, and agglomerates quickly, it means that the coffee beans you are using are very fresh.Especially when the coffee beans you use are roasted darker, the fresher they are, the richer and rougher the oils extracted will be. The reason for this situation is that fresh coffee beans contain a huge amount of carbon dioxide!As mentioned before, the essence of oil is a group of bubbles formed by carbon dioxide wrapped in the lipids of coffee beans. But when there is too much carbon dioxide, the oil cannot evenly wrap the carbon dioxide. In this situation where there is more gas and less fat, although there will be a lot of bubbles extracted, they will break up very quickly because their stability is not that high.Usually the flavor of concentrates containing this kind of oil is not very good. When you drink it, the flavor is either not obvious enough, or the taste is weak and the taste is light. 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 such oil in the espresso and the coffee tastes not that outstanding, it is best to readjust the extraction parameters or let the coffee beans rest for a while to ensure that the delicious taste of the coffee can be extracted in sufficient quantities.And if the extracted coffee creme is not as thick as before, but not rough, very delicate, very silky when shaken and can reflect light like a mirror, then this most likely means that the beans have entered.Appreciation period。Because there is no longer enough carbon dioxide in the coffee beans at this time that the lipids cannot be evenly wrapped, so 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 a richer flavor, and both the flavor and taste will be far better than the former.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 passed the taste period.Because there is no excess carbon dioxide in the coffee beans to form oil at this time, the oil extracted will be relatively thin.In this state, it will be easier for us to extract the soluble substances in the coffee than the former, and the coffee may taste better. However, it should be noted that since it is easier to extract soluble substances, it will be easier for us to dissolve those unpleasant substances in coffee, causing coffee to appear bitter, mixed, astringent and other negative manifestations.At the same time, the appearance of oil in this state also signals that we need to consume the coffee beans as soon as possible. Because the presence of carbon dioxide not only hinders extraction and the formation of oil, it also has the function of reducing the escape rate of aroma molecules in coffee.When there is a sufficient amount of carbon dioxide in coffee, the coffee aroma that contributes to the formation of flavor will escape much slower. When the carbon dioxide dissipates almost completely, the aroma in the coffee will escape faster. So it’s best to consume these beans quickly in a short period of time. Although we may be able to extract a fuller flavor from these beans, their appreciation period will be very short-lived.It is worth mentioning thatThe reason why Front Street always emphasizes the same extraction parameters is because we need to fix a parameter as our target for adjustment. For example, Front Street debugs the beans list every day.Front Street classic blendWhen the time comes, the target will be set first: extract 40ml of coffee liquid from 20g of powder 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 will also affect the richness of the oil. To give the simplest example: 20g powder and 30 seconds to extract 40ml of coffee oil will be richer than 20g powder and 15 seconds to extract 40ml of concentrated oil. So based on the above two situations, we first need to fix a parameter, and then start to compare~
You can now buy the above coffee beans online at the Taobao store “FrontStreet Coffee” (前街咖啡). FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou, China, and its Guangzhou retail shop sells coffee beans only. The shop carries dozens of coffee beans from different origins around the world, including carefully selected single-origin beans for V60 pour-over and espresso. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers.
The FrontStreet 2013 Yunnan coffee beans sold in the store come from the Typica variety grown at FrontStreet Coffee’s own plantation in Yunnan. The name comes from the year the brand and the plantation were founded. You can buy these beans from China’s Yunnan origin at the Guangzhou shop and at FrontStreet’s Taobao store.
FrontStreet coffee beans are freshly roasted within 5 days and deliver consistently excellent quality and great value. Orders placed before 17:00 are shipped the same day, and most areas within Guangdong Province receive them the next day.
FrontStreet Coffee Taobao store: https://qianjiecoffee.taobao.com
Or search for “前街咖啡” (FrontStreet Coffee) on Taobao
Important Notice: FrontStreet Coffee has moved to a new address: 315, Donghua East Road, Guangzhou (coffee beans only)
Tel: 020 38364473
