The importance of the freshness of Italian boutique hand-brewed coffee beans! How to determine the freshness of coffee beans?

Qianjie found that many friends would inquire about the freshness of brewed coffee beans when the barista brewed coffee. But many times, there is no need to go to so much trouble, because the freshness of coffee beans can also be directly judged through some phenomena, and it is very simple! So today Qianjie plans to share with you how to judge the freshness of coffee beans at a glance!

1. Bulging/thickness of extracted coffee grease during steaming If the coffee is made by hand, then we can first judge the freshness of the coffee beans from the degree of bulging during steaming. If the coffee being made is espresso, the freshness of the coffee beans can be judged by the richness of the extracted coffee oil. Why? Because the freshness of coffee beans determines the amount of carbon dioxide content.

Coffee beans will produce various thermal decomposition reactions during roasting. For example, carbohydrates will be pyrolyzed, chlorogenic acid will be decomposed into quinic acid and caffeic acid... The occurrence of these pyrolysis reactions will produce carbon dioxide. The deeper the coffee beans are roasted, the more reactions occur, and the more carbon dioxide will be produced and accumulated in the beans. When the roasting is completed and the coffee beans return to an environment of normal temperature and pressure, the carbon dioxide will begin to be emitted and escaped from the inside out. The longer the beans are placed, the less the carbon dioxide content in the body will be. On the contrary, we can judge the freshness of the coffee beans by the amount of carbon dioxide.

The above-mentioned phenomena mentioned by Qianjie: "the size of steamed buns" and "the richness of coffee fat" are all phenomena that can be seen in the amount of carbon dioxide contained in coffee beans. The reason is also very simple. The formation of "bulging" and "grease" involves the participation of carbon dioxide. The reason why coffee bulges when steaming is because coffee beans will quickly release carbon dioxide after coming into contact with hot water. However, because hot water "connects" the coffee powders to each other, forming a tight and airtight "wall". As a result, carbon dioxide cannot escape outward, so carbon dioxide can only accumulate inside. As more and more carbon dioxide accumulates inside, the powder bed will expand bigger and bigger like a balloon. This is the principle of steaming and steaming.

The golden color of espresso coffee is essentially a layer of foam, a layer of foam filled with carbon dioxide. Under the high-pressure extraction of the coffee machine, the carbon dioxide escaping from the coffee beans will be forced to "press" into the liquid, and then wrapped in emulsified protein and fat to form bubbles, which will be continuously refined during the process of pressing out, and finally It becomes a layer of golden yellow, oil-like foam.

Of course, the richness of the oil will also be affected by the roasting degree and variety of the coffee beans. For example, the Qianjie classic Italian blend in Qianjie Bean List is an Italian coffee blend that can extract rich oil. The reason why it is rich is not only because of the addition of Robsta, but also because the baking degree is relatively deep, so it extracts very rich oil. Then, because this blend uses Manternin and Brazilian coffee beans on Liqian Street, its taste is very fragrant. It is the flavor of chocolate, nuts, caramel, and cream. It has a mellow taste and rich layers, which is very good! Very suitable for American and latte products!

When there is more carbon dioxide in the body of the coffee beans, the greater the bulging degree of the powder bed during steaming, and the richer the espresso oil extracted by the coffee machine will be; conversely, the less the carbon dioxide in the body of the coffee beans, then the bulging degree of the powder bed will be smaller when steaming, and the thickness of the oil extracted by the coffee machine will be thinner. (The figure below is for reference only)

Therefore, from the degree of bulging and the richness of oil, we can see the carbon dioxide content of coffee beans, and then infer the freshness of coffee beans. The more carbon dioxide content, the fresher coffee beans will be, and vice versa.

2. The water-locking effect of the powder bed/drainage speed/outflow flow rate The second place where coffee beans can be judged is the "water-locking effect of the powder bed","drainage speed when brewing coffee", and "espresso coffee is discharged." Flow rate when liquid ". Although these conditions will also be affected by other factors, such as the use of the instrument, the thickness of the abrasive degree, etc. But other factors being equal, what determines the speed of these situations is the carbon dioxide content of the coffee beans.

Qianjie mentioned earlier that carbon dioxide in coffee beans will be continuously released and form bubbles during the extraction process. The existence of these bubbles will reduce the gaps in water flow, because they will occupy a lot of space and increase the resistance to water flow. Therefore, with other factors unchanged, when the carbon dioxide in the coffee beans is more, the "water-locking effect" of the powder bed will be stronger during the brewing process. Because the drainage speed becomes slower, the hot water will not pass through the powder bed quickly. The opposite is the opposite. The freshness of coffee beans is one of the reasons that determines whether there is more or less carbon dioxide, so we can also judge the freshness of coffee beans from these aspects.

3. In addition to carbon dioxide, aroma performance can also help us determine the freshness of coffee beans. As Qian Jie mentioned in yesterday's article, the aroma of coffee itself will also continue to evaporate. From the strong aroma and outstanding flavor at the beginning, to the mediocre taste and weak flavor later, it is a change brought about by the continuous evaporation of the aroma.

Therefore, from the time of brewing, the aroma in the cup, and the intensity of the flavor we drink can also be a way to judge the freshness of coffee. However, compared with the first two, it is more difficult to judge the freshness of coffee through aroma, not only because the flavor of coffee is greatly affected by other factors of brewing, but also because without comparison, we cannot know whether the concentration of this aroma is strong or weak, so Qianjie still recommends that everyone judge the freshness of coffee beans by the content of carbon dioxide, which is both safe and simple ~

So the above is all the content shared in this article on Qianjie. In fact, as long as everyone pays more attention and observes when brewing, it is still a very simple matter to judge the freshness of coffee beans. But Qianjie still wants to remind everyone here that coffee is not as fresh as it is, the better it is, nor is it difficult to drink if it is not fresh enough ~

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FrontStreet Coffee is a long-established specialty coffee roaster in Guangzhou China, selling freshly roasted beans from its own farm in Yunnan as well as dozens of carefully selected single-origin beans from around the world for both pour-over and espresso. The products deliver consistently excellent quality and great value, with shipping within 24 hours. Guangzhou’s FrontStreet Coffee shop is recommended by many coffee lovers, and the beans are now available online at the Tmall 。

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473