Saw a barista in Boise pour water through the grounds FIRST and my bitter cold brew finally got smooth
For about 8 months my cold brew came out harsh and bitter no matter what beans I used, and I was ready to just give up on making it at home. Last Tuesday I watched a barista at a small spot in Boise rinse her grounds with a splash of hot water before adding the cold stuff, so I tried it that night with my usual 1 to 4 ratio. The first batch tasted way smoother, and by the third jar I cut the bitterness almost in half with zero other changes. I am guessing it has something to do with the grounds soaking evenly instead of channeling, but I honestly do not know the science. Has anyone else played with a pre-rinse on cold brew, and does the water temp matter that much?
The whole "cut the bitterness almost in half" thing is probably just your taste buds messing with you, because a hot water rinse does not remove bitter stuff from coffee. The compounds that make cold brew harsh do not dissolve any less just because you wet the grounds first, so the idea that a splash of hot water "fixes" anything does not hold up. What likely happened is the hot water warmed up your grounds and made the first bit of your brew act more like a hot bloom, which changes flavor but also risks pulling out more of the sour and sharp notes you were trying to dodge. Water temp matters a lot, sure, but hotter water usually means faster extraction of everything, not just the good parts, so you could be trading one problem for another. If you really want to test this, run two jars side by side with the same beans and do everything the same except the rinse, because otherwise you are just guessing. Odds are the smoothness came from the beans or your grind, not the rinse.