I've been wanting to play around with cold brew, having never really explored it much. I know the standard for cold brew is a coarse grind (or sometimes "extra coarse"), and either 12hr on the counter/room temp, or 24hr in the fridge. I felt like this style of recipe came about before Perger et al really came out and said we should be grinding much finer for immersion, rather than coarser. So I wanted to test that.

I have done a couple tests recently with a finer grind - the same grind setting I have been doing pour over at, for a single cup V60. The first test was a simple room temp using my Breville Precision Brewer's cold brew function, using a 1:10 ratio. I sampled it a couple times during brewing and the best results were within 4-6hrs (I stopped at 6); at 4 hrs it was a little weak but tasty, and 6hrs would be a good time to stop for those wanting a smooth, high body brew with some character/flavor.

The second test I did was a sous vide brew, having heard the higher temp gets some more flavor/acidity. I did 165F for 1hr and it was over extracted, which surprised me a bit with the "short" brew time. I did do 1:14 for this one, so it probably extracted too easily, and it didn't reach a good strength in that amount of time, which surprised me a bit given the temp, grind size, and that it otherwise was bitter/over extracted.

This is where I'm interested in further exploring "cold" brew, which I think might more appropriately be labeled "slow brew" since there is some active heat involved. Has anyone here played much with sous vide temps and brew times? I am curious if I should do 165 for only half an hour, or maybe use an even finer grind to get strength up, etc? I have a feeling an espresso grind with a 1:6-1:8 ratio would be a better improvement than trying to go shorter on the brew time.

I'm also curious to start a discussion on cold brew temps in general. 37-40 F fridge temps vs 65-75 F room temps vs these higher sous vide temps. Thoughts?

What about hot blooming - I've tried this a couple times before and liked the acidity it brought. Has anybody taken temps with hot blooming and compared to sous vide/slow brewing?

This is actually the first time that I've heard using a sous vide for cold brewing. About how long did you brew with it? Pretty amazed at all the different things that I can use this kitchen tool for now (infusions, cooking, and now brewing?).

I think the "usual" recipe is 150 F for 3 hours. I haven't actually tried that one out. I think it opens up a lot to play with when it comes to temps, but I'm thinking the ones above 150 might require quite short brew times... I did that 165 F for 1 hour and it was likely too long, or I need to do a coarser grind.

Not surprised that 1 hour was too long for 165 F, that's basically serving temperature for coffee.

But honestly it wasn't that bitter, so it seems like only a small adjustment is needed. I am under the impression a higher temp will help pull more acidity and character out of the grinds, so I'm just trying to find the right balance that makes for an interesting enough coffee that is "elevated" above traditional cold brew in a shorter time frame.

In my experience with other immersion methods, such as FP vs Turkish, I am grinding much finer for Turkish and still ending up with a similar brew time, due to the much higher concentration (1:4-1:8 for Turkish instead of 1:15 for FP). The Turkish takes on a great taste at this ratio compared to the same ratio in an FP, because the difference between the brew styles is that the FP is losing temp the whole time, and the cezve is increasing heat the whole time and is able to hit a higher max temp this way. Even if using boiling water for the FP and with the total water (and therefore heat delivered) being greater, it does not hit temps above 200 F like I have measured in my cezve.

I think with this in mind, since sous vide is applying heat the whole time similar to Turkish, I may even be able to go finer and shorter at a higher temp given the right ratio.

I've got some extra beans that I might try out here using the 3hrs @150 rule and see how it turns out.

Will post back.