I mainly make flat whites using 16g of coffee at a 1:2.5 ratio. It wasn’t bad with 140–150 ml of milk, I could always taste a strong coffee flavor, but there was also some bitterness.
Recently, I tried a 1:1 ratio for 25–30 seconds and increased the dose to 19g. Surprisingly, the coffee flavor was just as strong as with the 1:2.5 ratio, using the same amount of milk, but with no bitterness at all.
Is the lack of bitterness simply because there’s technically more milk relative to the espresso, or did the extraction ratio, time, and grind size make the difference, knowing that it’s usually suggested to increase the yield for a less bitter drink?
edit: sorry i initially missed up when i mentioned the 1:4 ratio in the post, what i mean't was 1:2.5