So I just brewed an oatmeal stout (a recipe I've done before). I seem to remember this happening back then, but I still want to see if anyone agrees. My beer went through the normal stages, no big issues to speak of. I had a slight stuck fermentation, but I made a small starter and re pitched, and then waited about a week (gravity readings had settled). The only other thing I did differently was that I cut the secondary short by a week, because I added vanilla beans to the secondary, and vanilla tends to vanish quickly so I didn't want to wait too long.
I cold crashed, then kegged, carbed, and left it in my keezer. Took a taste after about a week of carbing and it has a sourish taste. Not overwhelming, but noticeable, probably because stouts shouldn't be sour.
Now the recipe I used had me soak raisins in rum, and add them to the end of the boil. I seem to remember this giving me a sourish taste last time, but it had disappeared by the time I bottled last time.
I always assumed that the sour taste was due to the raisins. They are grapes, at the end of the day, and a slightly sourish taste is something I'd expect. My only fear is that this won't go away like last time. I'm pretty confident in my sanitizing methods, star san everything diligently.
Any thoughts? Could this just be that I need to wait longer since I added more yeast and dme (boiled and then chilled), so I need to wait longer? Obviously any infection is possible but like I said, I was super diligent. Plus, there's no sour smell or pellicle. I can obviously afford to wait longer, I just hate to wait and then find out it was always garbage. Don't like wasting time.
I could always add more vanilla and/or lactose. Since it's in the keezer, any infection wouldn't be able to turn lactose into more sourness, but I don't want to put lipstick on a pig. I also have a spare keg, so leaving it for a while wouldn't be wasting the real estate.