Originally Posted by BOBrob
Looking back on previous posts.... I would say give things more time. Sounds like sour, green beer. You can hit your gravity in a short time ,but the yeast has to clean up to make decent brew.
Thats a good point, Acetalaldeyde (Green apple/ jolly rancher flavor) can come a cross a sour note. I learned this in my BJCP prep class the other day that Bud light has a good amount of acetalaldehyde in it. A good test might be to get a bud light, and give it a good smell and taste. It comes on very strong the first taste. Think about green apples or green apple jolly ranchers, and it will be easy to pick up on.
If this is the sour flavor you are getting it is likely what Bob is talking about, beer that was racked off the yeast cake a little too early and is a little young.
One thing to taste for if you have an infected batch is Diacetyl, butter flavor or the feeling of a slick coating on your tongue. Souring bacterea like pediococcus or lactobacillus will produce a lot of diacetyl so if you have an infection with a souring bacteria you should detect diacetyl's presence in the beer.