Sour milk smell for milk stout?

[Peruvian802]

I brewed a chocolate milk stout, adding lactose with 10 minutes left in the boil. The beer tastes fine but it has a tinge of a sour milk scent, particularly when it's fresh poured and cold. Is this normal? Is there anything I could or should do in the future to avoid this?

 

[TheZymurgist]

That's definitely not normal, and my only guess would be that you have some sort of infection. Sorry I can't provide more info, but I've never had that issue.

 

[amcclai7]

My girlfriend has a tendency to leave milk around the house. A half drank glass here, a non rinsed out jug in the trash, etc. As a result, I am very sensitive to the sour milk smell. I have to follow it with my nose all around the house until I find and dispose of the culprit.

I also have had several people tell me that all milk stouts have a twinge of that aroma to them and ever since I've been living with her I've started to notice that as well. If its minor and it dissipates (or perhaps you're just getting used to it) over time then I would bet you're just highly sensitive to that aroma just like I am.

 

[Peruvian802]

^^^thanks for the reply. I think that a beer's aroma is one of my favorite parts and is why I noticed the scent. I've asked several others who have tried this stout and no one else has noticed it.

 

[TobyG]

A sour milk smell would generally be caused by lactic acid. It can be caused by a bacterial infection, or it could just be that you're hypersensitive to the aroma from adding lactose pre-fermentation (it will ferment at least somewhat). My wife doesn't like most milk stouts for that reason. Thankfully, I don't have that particular sensitivity.