The relationship between the extraction amount of Espresso and the extraction time? What is the pre-wetting in Espresso extraction?

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Qianjie Coffee briefly describes pre-wetting (Pre-infusion, also known as pre-soaking): the act of infiltrating coffee powder in an espresso machine before it is actually extracted. Some coffee machines are achieved through pumps; the pump works for 1 / 2 seconds and stops for 1 / 2 seconds. Then start to continue to extract coffee, full automata and some automatic machines use this way. After the pump starts, the pressure is completely applied before the coffee cake, and the second cavity must be filled. The soaking time for coffee powder was 3-7 seconds before the pressure was established. This kind of prepreg is more popular. There is a car saying that progressive pre-wetting can improve the extraction of coffee.

Tiger spot stripes and variegated spots: the main visual cues for good extraction. The tiger spot is formed by the contrast between dark and light coffee oil in the coffee stream; ideally it appears at the beginning of the coffee and lasts until the end. "mottling" is the expression of extraction in a cup; refers to dark brown spots and reddish brown markings formed on the surface of coffee oil.

Proper extraction: refreshing fruit acid, Mena reaction compound round and warm taste

Al's Rule extracted by espresso (Al-Fe rule: sweet spot formula)

Al Critzer's understanding of Espresso extraction has become the most common concept of Espresso in Europe and America. The translation is as follows:

Start with the result that 30cc/ 30sec gets a perfect Espresso. These two values of course depend on beans, and the differences in baking method, baking degree and formula ratio will naturally lead to changes in the reference point.

The amount of extraction is inversely proportional to the extraction time: the more the amount of extraction, the shorter the contact time between coffee powder and hot water (to avoid over-extraction). On the contrary, when the amount of extraction is reduced, the contact time between coffee powder and water should be increased (to avoid insufficient extraction).

Al formula: when the extraction amount of 5cc is increased, the extraction time should be subtracted from 1sec. On the contrary, add 1sec.

For example, when the amount of extraction increases to 45cc, 30-(45-30) / 527, the extraction time is reduced to 27sec.

When the extraction amount is 60cc, the extraction time becomes 24sec.

Within the reasonable limit of Espresso of 0.75-2.5oz, this formula can quickly and correctly hunt sweet spots (Sweet Spot), effectively catch satisfactory ingredients, and maintain the balance between over-extraction and under-extraction. The main means of control is to adjust the grinding thickness.