Coffee powder the easiest way to drink coffee beans must be ground into coffee powder before brewing?

Coffee drinkers always say that coffee beans should be ground immediately before making coffee, because once it is ground, it will have more surface area, which oxidizes the delicious things in the coffee. This is just a subtle distinction that only serious coffee snobs will notice, or can anyone notice? After grinding, the easiest way to drink is to brew with a hanging ear filter bag, and an interesting experiment can be done below. See how the coffee flavor changes.

The coffee is from Yegashefi Yergacheffe, Ethiopia in Metropolis. It was baked 15 days ago. Four batches were tested and ground at different times:

Fresh grinding (a few minutes before brewing)

Eleven hours ago, each batch of 16 grams (2 Aeropress spoons) of coffee was ground (not as fine as espresso) in a blade grinder and stored in a small sealed plastic container. Preheat the Aeropress in hot water so that the first cup of coffee is not made from colder water than the later cup.

Brew coffee using the standard Aeropress method: pour the measuring cup into the 2 mark, pour into the chamber containing the coffee, stir for 15 seconds, then press. The water temperature is close to 185 degrees each time. Because the coffee coming directly from Aeropress is very concentrated, it is diluted with the same amount of water (although this is actually a little more diluted than I usually drink). Finally, add 1 cup and 3 teaspoons of sugar to each cup.

Fresh grinding: brighter acidity and the strongest flavor. I will use this as the baseline for comparison.

9 hours: very similar to freshly ground coffee, though a little mellow; less "bright" notes.

24 hours: some of the fruit flavors fade; the taste is generally a little less.

7 days: darker, and the overall flavor decreased obviously.

Surprisingly, it's hard to decide whether you prefer freshly ground coffee or 9-hour coffee. Freshly ground coffee tastes a little better and has more acidity, but it does enjoy the richness of coffee for 9 hours. As the coffee cools, it's hard to tell the difference between the two.

24-hour coffee is different from freshly ground things, but not very big. Without a side-by-side comparison, it is impossible to tell that it has been ground the day before-just because of different brewing parameters, the coffee may change more from day to day.

7-day coffee is really not as good as other coffee, but it is still more delicious, such as Starbucks coffee. This test is far from perfect and has many possible confounding variables; some differences in flavor may be due to different sizes of grinding, temperature and brewing time. But at least it is known that grinding one day in advance does not have much effect on the taste of this coffee. There may be a bigger difference for fresher or better coffee-even though these things are very good.