How do I know if home brews are safe to drink?

Question

I received a true beginner's homebrew kit from a relative as a Christmas gift, decided to attempt a brew and followed the directions as close to perfect as I could.

After the entire process was completed I wound up with something that did not really pour, smell or look like beer. Obviously I have done something wrong and need to try again, but my question is:

Assuming an enthusiast observes a respectable level of sanitation in the process of the brew, but perhaps severely deviates from the instructions at some point in the process, how can they tell if their brew is actually fit (or unfit) to drink? Are there tell-tale smells/colours/heads that indicate a "spoiled" beverage?

Answer 1

I have personally drunk beer that was unintentionally sour, and smelled like a sewer, without a problem.*

If it has alcohol, and a low-ish pH (was made from reasonable water, barley and hops) then it is, according to history, safe. Many contaminating bacteria will produce acetic or lactic acids under these conditions, but they are also safe to drink.

If you really screw things up, (forget to add yeast, drop dead mouse in there) maybe its possible to grow some listeria or something, but you'd probably find the smell to be intolerable.

Typical beer infections will produce various levels bad flavors along with some scum on top of the bottled beer (since yeast produce bubbles and foam when working, this scum might not be visible until the yeast are completely finished, usually after the beer has been bottled). Some kinds of bacteria will also give a ropey (snotty) texture to the beer, but even this is safe to drink. This page lists common beer off-flavors, note that danger isn't discussed, because there really isn't any.

And if you contaminant is a wild yeast, the beer might turn out OK (or even great) after a long aging, despite initially smelling horrible.

*Not a beer that I made