What's the difference between coffee freshness? How to tell if coffee beans are fresh?

With the gradual popularization of coffee culture, more and more friends begin to realize that coffee also needs to pay attention to "freshness", because fresh coffee always has more aroma substances and can bring us a richer drinking experience. However, because most of the aroma substances are volatile, they will gradually lose over time, and the freshness of coffee will decline.

Generally speaking, the main basis for determining whether a cup of coffee is fresh or not is its baking time and its taste. Because these two are more direct and accurate ways to let us know the freshness of coffee itself, Qianjie has re-introductions in previous articles, and people who are interested can learn about them by searching and flipping through previous articles. In addition to the above two judgment methods, we can also through other aspects of performance to see whether coffee is fresh, that is, they are relatively less direct, need to be combined with the taste to judge. But this is also a little trick to know the freshness of coffee in advance, so let's share it in front of the street today. What else can we observe the freshness of coffee?

First of all, we can judge the freshness of coffee by smelling the fragrance, because, as Qianjie said, the fresher the beans, the more aroma substances they contain. So after the coffee beans are ground into powder, we can make a simple judgment by smelling incense.

Fresh coffee beans give off a very rich aroma after being ground into powder, from which we can capture some specific flavor characteristics, while coffee beans that have been kept for a long time because the aroma has almost dissipated, so they emit more of the taste of baking, the flavor is relatively not so easy to capture.

Second: the richness of the foam it doesn't matter if you can't smell it because of a stuffy nose or some other reason, because coffee also has many obvious characteristics to reflect its freshness. For example, in the steaming stage of hand-brewed coffee, the drum degree of the powder bed is a good observation object.

When the extraction parameters are normal, fresh coffee will bulge a large bag during steaming because of the abundance of carbon dioxide. The fresher the coffee and the more carbon dioxide, the bigger the bulging bag. On the other hand, coffee beans that are not so fresh have less bulging bags because they are not so rich in carbon dioxide. In addition to the drum bag, the "water locking degree" of the powder bed during steaming can also be used as an object to judge the freshness. Because the presence of carbon dioxide can be a hindrance, it hinders the infiltration of hot water. When there is more carbon dioxide in the coffee, there are more obstacles and the slower the speed of launching. At this point, we can observe the wetness of the powder bed, whether it remains moist after the steaming is over, or whether it has dried up as early as 20 seconds. This is another small feature to judge the freshness of coffee beans.

However, it should be noted that these two characteristics (drum degree, water lock degree) can only see a general range of coffee from the roasting time, and they can not be used as a basis for judging whether coffee is good or not. Because most light roasted coffee still tastes good after it has been kept for a long time, it has something to do with their density. Therefore, these two characteristics can only be used as a judgment of the distance from the roasting time of the coffee bean, and it has to be determined by combining the taste.

Let's talk about espresso. After all, many friends consume mainly espresso every day. Similarly, espresso can also be used to judge the freshness of coffee by its aroma and the state of coffee at the time of extraction. When making espresso, the main thing that can judge the freshness of coffee beans is its oil, and the rich and delicate degree of oil is the object that we can observe.

Because the oil components of espresso are mainly carbon dioxide and the lipids of coffee beans, the more fresh the coffee beans are, the more carbon dioxide they contain, and the more oil they produce during extraction, but at the same time they are rougher. This is mainly because the oil of espresso is essentially a myriad of tiny bubbles filled with carbon dioxide, and the more bubbles are produced, the easier it is to break, because the structure is less stable. so their quality is relatively poor and easier to break.

When the coffee beans are stored for a period of time (starting on the 7th day after roasting), the amount of carbon dioxide is reduced, and the extracted oils are not as rich as before, but they are much more delicate. Because the structure of bubbles is more stable and less easy to break. In the future, the coffee beans will have less carbon dioxide, and the extracted coffee oil will be thinner and thinner. So we can know that the richness and delicacy of oil can become a measure of the freshness of coffee beans. But again, they can't be used as a measure of whether coffee tastes good or not. At the same time, we need to note that there is a great difference in the thickness of the oil extracted from deep-roasted coffee beans and light-roasted coffee beans, because the amount of carbon dioxide that can be contained in their bodies is completely different. therefore, do not apply the standard of deep-roasted espresso to the extraction of light-roasted espresso, otherwise it will lead to misunderstanding.

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