Caffeine has a charming taste because of its complex chemical composition, but it is also fragile, perishable and difficult to store. At present, the decay mechanism of mature coffee beans can be roughly classified into four categories:
1, volatile. Coffee will produce a lot of volatile aroma after roasting. In addition, coffee will emit a lot of CO2 gas after baking, and it will also take away many aromatic substances. For example, the caramel flavor and sweetness of flowers and plants will soon disappear.
2. oxidation. Most of the aroma produced by coffee roasting is unstable. When it comes into contact with air, it will be oxidized to produce some smells, especially protein and oil. After oxidation, it will produce stale smells. Some expired beans have a musty smell and a rotten stench, which is probably the reason.
3. Hydrolysis. When the air humidity is too high, the coffee beans will get wet, the internal substances will be extracted in advance, and hydrolysis will occur, and some aromatic substances will be transformed and disappeared.
4.Mena reaction. Mena reaction can take place at room temperature, and the complex chemical components in coffee will interact, slowly degrade or polymerize, resulting in many off-flavors. Low temperature storage can inhibit the reaction to some extent.
In a word, the preservation of coffee beans is a university question. The discharge of CO2 and aromatic substances, as well as the entry of outside air and water vapor, make the quality of coffee beans vary greatly. Coupled with the chemical formula of coffee beans and other factors that affect the reaction speed, it is really difficult to make coffee fresh and lasting. The famous illy company uses inert gas to pack coffee cans under pressure, claiming that it can inhibit the volatilization of coffee aroma. This has also become its patent, but it has greatly increased the packaging cost.
It is the most common package with one-way exhaust valve at present, which can slow down the decline of coffee to a certain extent and the cost is not high. Many home baking cafes use this kind of packaging. Some people advocate packing coffee and putting it in the refrigerator, which is also controversial. But the best solution is to "drink as much as you want" and use it up as soon as possible. Cabbage has specially introduced100g of fine coffee (generally 227g). Drink one cup a day, which is almost the amount for a week. Drink it before you buy it. Only in this way can you drink fresh coffee forever.