I brewed on Monday but pitched over 48 hours later on Wednesday, because my temperature control was finicky and I wanted to wait until the wort hit the proper temperature before pitching. Normally I would wait only 1 minute to 12 hours until pitching.

However, before I pitched, I noticed clear signs of fermentation: the white bubbly layer on top of the wort and a bubbling airlock. I can only presume this is some form of contamination. I pitched the yeast anyway and will hope for the best.

However, I would like to know the following:

Given that my wort started fermenting before I pitched the yeast, does this imply that the beer would have been contaminated even if I had pitched earlier, that my sanitation was poor? Or, is it simply the nature of the beast that wild yeast and other stuff will get in the wort regardless of my sanitation habits, and now they have a 48 hour head start on my yeast strain?

Was it poor sanitation or is pitching 48 hours a bad idea in general?

  • 3
    just to add to the theme without answering your question: I think pitch a little hot is much less dangerous than waiting 48hs to pitch. brulosophy.com/2014/12/15/…
    – jards
    Commented Sep 10, 2015 at 20:35
  • 1
    As an update, my brew turned out horribly contaminated. Commented Apr 5, 2016 at 18:39

2 Answers 2


QUICK TIP: Did you check with a hydrometer before you pitched? The golden rule with determining fermentation is "Trust your hydrometer; Almost everything else will lie to you" - Bubbling airlock and foam on the top of the wort can all have other causes, while a drop in specific gravity is only caused by conversion of the sugars in the wort to alcohol.

However, the likelihood here is that you've got some kind of unintended fermentation going on, and there are a couple of possible causes for that:

1) You had a bit of yeast left over unnoticed in you fermentation vessel from a previous brew; They can hide in all sorts of places, be particularly suspicious around taps, since they're very hard to properly sterilise!

2) A wild Yeast got in there; When you pitch a big load of brewer's yeast into your wort you give the brewer's yeast a huge headstart in terms of number and viability, so they tend to out-compete the infinitely more fragile wild yeasts and give them no chance; The delay in pitching could have given the wild yeasts the chance to establish themselves.

If you're lucky, it's 1, and your brew might have a slightly different yeast character, but be ok... If it's 2) then it's a dice roll; You might have discovered that you have an awesome local yeast which creates the next greatest beer... Or you might make a few gallons of vinegar... Wild yeasts are unpredictable at the best of times...

Either way, to answer your question, it's probably more down to late pitching than poor sanitation, but be carefult to clean taps and other hotspots thoroughly in the future...

  • Good points, though I feel like 'infinitely more fragile' isn't a great way to describe wild yeast. They do get out-competed, but it's kind of like saying a tank is infinitely more fragile than a soldier because it can't compete with 40,000 soldiers. Commented Sep 11, 2015 at 6:50

Although it is possible to get dissolved gasses out of liquids by heating them, making it look like there is fermentation, there really shouldn't be much gas dissolved in a recently boiled wort.

Instead I think you have done a 'forced wort test' by delaying your pitch. The test is simply: make wort, don't add yeast, wait until something happens spontaneously. Having visible signs of fermentation in only 48 hours means poor sanitation. What you really want is 4 or 5 days, or longer, before spontaneous fermentation / cloudiness / strange odors happen.

As The All Powerful mentioned, it could be yeast, which should at least result in drinkable beer. If it's something else, you may want to chuck it. Take a sniff at the airlock: if the smell is questionable, keep the beer; if the smell says 'kill it with fire' you'll know what to do.

Your last question: yes, its poor sanitation and yes, waiting 48 hours is a bad idea.

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