The main reason for steaming coffee? How is espresso "steamed"?
Steaming by hand is an important action used to release carbon dioxide from coffee powder so that subsequent water injection can better extract aroma substances. If this action is cancelled, it will bring many unstable factors to the subsequent extraction.
However, the extraction of Italian coffee is relatively "rough" a lot. The aroma substances in coffee powder are "pressed out" directly using high-pressure hot water. There is no "stewing" process during this extraction period. Therefore, some friends will be curious, if the espresso extraction is also added to the steams, what changes will be made to the final coffee? In fact, adding "stewing" to Italian extraction has been done a long time ago, and has become part of the coffee shop extraction daily, and it is the "pre-soak" that we hang on the lips.
What is pre-soak? Usually, when we make espresso coffee, we use the factory default pressure of the espresso machine-"9bar" for continuous extraction. The so-called pre-infusion means that before using full pressure (9bar or more) to extract coffee, water is first used to penetrate the coffee cake, and then the water is stopped for a period of time to allow it to soak, and then the extraction operation is repeated. This behavior is called pre-soaking, meaning pre-soaking before extraction.
Its role is to make coffee powder achieve the effect of exhaust by pre-soaking (consistent with the principle of hand steaming behavior)! So, for concentrated extraction, what effect will the addition of exhaust have on subsequent extraction?
The first use of the pre-soak feature is to increase the extraction rate! When the cake has been pre-vented, the subsequent full-pressure (9bar) extraction will make it easier to obtain soluble substances! Especially for fresh coffee beans, which have a lot of gas, they are best used for pre-infusion operations. When we use fresh coffee beans, the large amount of carbon dioxide contained in their bodies not only makes the extracted oil very rough, but also makes it difficult for hot water to extract the aroma substances of coffee, and it is easy to have a series of negative feelings such as insufficient extraction and rough taste.
Then at this time we can improve these problems by pre-soaking. When these carbon dioxide that hinders extraction is discharged, we can extract the aroma of coffee more easily. This is what we often say to improve the extraction rate. And the problem of rough grease and so on naturally has also been improved ~ and, it can also reduce the channel effect, this is its second use! Since conventional extraction uses a high pressure of 9bar throughout the process, it is very strong. If we do not distribute the powder evenly when filling the pressure, it will lead to hot water breaking through the weak and less powder places along the high pressure during extraction, and then a channel effect will occur.
Channel effect will lead to a serious non-uniform extraction, and pre-soaking can solve this problem properly! When we use pre-soaking, the coffee powder will expand first under the soaking of a small amount of hot water, so that the powder cake can be more compact and no longer prone to perforation. Therefore, we can conclude that increasing the extraction rate and improving the extraction are the special advantages of pre-soaking. However, in order to give full play to these advantages, there must be a prerequisite, that is, it needs to be used properly! Most machines do not have a one-button presoak extraction function, so we can only use manual control presoak!
When pre-soaking water injection, we can choose low pressure or no pressure to inject it, because if the pressure of 9bar is directly used for pre-soaking, it is easier to break through the powder layer on the coffee surface and appear channel effect;
Then the soaking time only needs to be set according to the freshness of the beans. The fresher the beans, the longer the soaking time. Only enough time can make it emit sufficient carbon dioxide. 5 to 10 seconds is a selectable range. For beans that are not so fresh and for deep-baked beans that are well developed, there is no need to pre-soak them because they are easy to extract themselves!
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