Is there a way to know yeast infected before pitching?

Ok, my last two batches have been infected by something (or at least im pretty sure they were infected: very bitter and sour aftertaste). I am assuming it was the yeast which was washed from previous batches. One was about 6 months old and the other was on its 3rd generation. Both I had in mason jars in the fridgerator. I have used washed yeast about 5 times prior with no problems. I think maybe there was some rust on the mason lids or something from the previous primary that infected the yeast.

Is there a way to tell if yeast is infected while im doing my starter by smell, etc?

Is 6 months in the fridge too long for washed yeast?

Also, when washing i am just pouring the water/washed yeast from carboy into mason jars. Should i be siphoning instead? (using wash yeast thread boiled jars, water, etc.)

Am i correct in assuming it was probably the yeast that is causing this very bitter and sour taste in the beer? I pretty good with de-con of carboys, brewing equipment, etc.

Hard to say... It could be the yeast or something with your process.

The easiest way to tell if the yeast is bad is by the smell. If it doesn't smell good, don't use it. Another way is to taste it. Again, tastes bad, don't use it.

I never use washed yeast past one month in the fridge. That's me. I wash with sanitized water and then pour into mason jars as well. I throw in the fridge at 38F and leave it there. I do a starter if needed (use Mr Malty calculator to determine).

Thanks for response Pearson.

Yea so maybe yeast was old or something. Bummer man! Only other thing i can think is i have added dextrose to both of these batches during boil to kick up the alcohol content. Could this have anything to do with sour taste?

Please don't take this the wrong way, but are you sure it's sour? If so it's almost certainly contamination. If it's just an unpleasant character though, that could be yeast stress (underpitching, pitching/fermenting too warm, etc.)

Dont worry I wont take it the wrong way! Lol ive been only brewing a year and these are the first "off" batches i have had, so no im not entirely certain its sour. It has also only been in primary 3 weeks, but doesnt seem to be improving. Def could be yeast stress i guess (just not sure what that tastes like). The temps should be good as i have them in a fridge with temp control. I have heard that if it gets worse (i.e. more sour) over time thats a sign of contamination. and it seems that is what its doing

this is what fermenter looks like:



i have looked up some contaminated pics and this looks like first stages

Sounds like a good excuse to go pick up a sour beer at the liquor store and compare!

For me, infections tend to smell and taste like vinegar, and therefore easy and quickly disposable.

Other smells and tastes, such as apple, are characteristics of poor yeast management and use.

my 2c

kenlock said:

For me, infections tend to smell and taste like vinegar, and therefore easy and quickly disposable.

Other smells and tastes, such as apple, are characteristics of poor yeast management and use.

my 2c

Click to expand...

Good point... I should've expounded on my 'off smell' comment. Off smells can be acetic (vinegar), enteric (intestinal), rotten meat (not rotten egg, that could be sulfur - and acceptable depending on the yeast strain) and, of course, vomit. I know those are pretty strong smells, butthey happen. It's funny, but most people just naturally know what 'good' yeast smells like. We picture that 'bready' smell. The opposite is also true, we typically know what 'bad' yeast smells are too. The only one that pushes people is that sulfur smell since it's rotten eggs, but many yeast produce that smell during fermentation and it goes away when done.

thanks for the input guys. yes im pretty sure it is definitely contaminated now. Even though i have brewed about 20 batches of beer, i still second guess my instincts of good and bad beer. looks bad, smells bad and tastes bad: must be bad! lol. still learning!