bit of mold & bacteria will not be a problem for most of us.
yesterday, at Panajachel (staying here for 3 days), I had a huge snail soup. and of course, I ate that darn thing... ha ha ha
OK Snail soup would be a problem for us here. I'm OK with eating frog, alligator, but have never been able to get past those, my limit- but food is for another time and another forum. :exclamation: LOL
Yes, leaving out coffee for days on end is no good for anyone. I'm not a scientist- I'm going off of what we've done practice wise and experience given to me from other Baristas. These are just ideas to try. But a 4 to a very maximum 24 hour brewing time (<--as long as its still actively dripping) with refrigeration immediately after in a sealed container or craft has been no problem for us.
We've never had an issue when using clean glass and water- in fact the few barista's who I've talked to have never had an issue with cold brew concentrate. The magic number for great cold brew is 6 to 12 hours. Like I said in a past post, we set our drip rate on the drippers for a 6 to 8 hour drip rate to completely empty the icewater from the top craft- then refrigerate once the drops have slowed.
Of course with cold brew, it tastes better the day after brewing & refrigeration. It needs to rest overnight in the fridge for a good robust flavor.
The amount we make, and with people stopping by our woodshop for a cup of coffee- we go through a gallon in 4 days.