How Long Can Beer Sit Before Adding Yeast? (Don’t Risk Infection!)

Most homebrewers know that if you pitch yeast too soon, your wort may be too hot and kill or damage your yeast. But waiting for the wort to cool can take a while, and there are plenty of other surprises and interruptions that can delay the pitching of your yeast. How long can that wort sit before pitching?

It is best to pitch yeast as soon as the wort reaches the ideal fermentation temperature (between 65-72 degrees). However, it is usually okay to pitch yeast within 24 hours of removing the wort from the boil, provided you keep the wort covered the whole time to reduce the chances of infection.

Any exposure to air creates an opportunity for the wort to be infected by bacteria or yeast naturally occurring in the air. Since you won’t be storing the wort in a vacuum, it will naturally be exposed to a small amount of air, even if covered. Every minute the wort spends sitting before fermentation begins comes with a small amount of risk of infection.

How long can you leave wort before pitching yeast?

There’s no hard and fast rule as to how long wort can be left out before pitching yeast.

Factors like the ingredients in the wort, the temperature of the wort, as well as the amount and type of bacteria and yeast in the air will impact the amount of time it would take for an undesirable infection to occur if you wait to pitch yeast.

It’s best practice to pitch yeast as soon as the wort has reached optimal pitching temperature, however, most homebrewers agree that waiting 24 hours or so is typically not a dealbreaker.

What are the risks of leaving wort out prior to fermentation?

Wort is extremely susceptible to infection by two primary things:

  • bacteria
  • wild yeast

Bacteria

Wort left exposed is subject to the bacteria in the air, most of which are undesirable in any beer recipe. The most common type of bacterial infection in beer is from the Lactobacillus variety.

According to one study, Lactobacillus bacteria are responsible for 60-90% of unwanted infections in beer. Though not a danger to hot or boiling wort, these bacteria thrive in room temperature conditions, though they generally take 24+ hours to really develop. 

Wild Yeast

All of the qualities that make wort an optimal environment for fermentation by the packet of brewers yeast you drop in also make it susceptible to wild yeast. Wild yeast is just that: yeast that occurs “in the wild”, or, naturally in the air.

If you were to leave wort exposed at room temperature for multiple days, it’s also likely it could be contaminated with wild yeast and actually begin fermenting.

Though there are ways to harness and control this, it’s not easy to do as a homebrewer, especially if it happens by accident. 

Cooling wort before pitching yeast

When it comes to pitching yeast, it’s also important not to rush it.

Wort that’s still boiling or even too hot can kill yeast, meaning fermentation will never start. Most brewer’s yeast comes with a recommended pitching temperature. For many beers, this is right around room temperature.

Check out this article for more info on what temperature kills beer yeast!

It can take quite a while to cool wort by simply placing the kettle in an ice bath so many brewers use a tool like a wort chiller to help accelerate the cooling process.

Can you pitch yeast the next day?

Maybe you forgot to pick up yeast at the homebrew store. Or maybe you went to pitch your yeast and found it was dead and you needed to buy some more the next day. Either way, you may be wondering if you can pitch your yeast tomorrow. If you must push your pitch time forward a day, seal it tightly. 

You can keep it refrigerated, but keep in mind if your target pitch temperature is room temp, you’ll need to let it sit at ambient temperature for several hours to reach that temp again. If it’s just going to be 24 hours, you can typically let the sealed wort sit out at room temperature without issue.

What happens if you forgot to add yeast to beer

Okay, what if it’s days after the boil and you wake up in a cold sweat because it hits you: you forgot to pitch the yeast at all. Is there anything to be done?

If you find yourself in this position, take a deep breath and follow these steps:

  1. Visually inspect your wort. Yes, it’s still wort! Depending on how long you’ve left it languishing, it may be okay. Look for unusual or fuzzy growth on top. This can be a warning sign of a bacterial infection. If it’s got something growing on it, it’s probably best to dump it and start over.
  2. Smell it. It should smell pretty much the same as it did when you put it in the fermenter. If it has a sour or funky smell, bacteria or wild yeast may have moved in.
  3. Take a taste. If it looks and smells okay, take a taste! It should still taste quite sweet since none of the sugars have fermented.
  4. Pitch your yeast and cross your fingers. If it passes the sight, smell, and taste test, pitch your yeast! It’s possible that your stellar sanitation practices and tightly sealed fermenter have saved you this time. Keep a close eye on this batch and look out for any off flavors. 

Tips for getting fermentation started quickly

If you pitched your yeast later than expected, you may be searching for ways to jumpstart fermentation a bit. Luckily, there are some concrete things to try to make sure your yeast hit the ground running. 

To get your fermentation started as quickly as possible:

  • Use a yeast starter
  • Pitch extra yeast
  • Aerate the wort

Use a Yeast Starter

It’s always a good idea to keep a yeast starter on hand when homebrewing. A yeast starter is essentially a mini-batch of homebrew that you can get started in advance. This will activate your yeast in advance of adding them to your wort or beer. This activated yeast is already doing its thing so it will cut down on the time it takes fermentation to begin.

Pitch Extra Yeast

You’ll want to be careful with this method, but pitching a bit more yeast can be a sneaky way of creating a quicker, more robust fermentation. Fair warning, pitching too much yeast can ruin your beer with off-flavors, however, a little bit extra can ensure there is plenty of healthy yeast available to get started.

Aerate the Wort

Yeast needs oxygen to thrive so giving your wort a vigorous stir will introduce a bit of extra oxygen. You can aerate the wort either right before or right after you pitch your yeast, however, only do it once, then let fermentation commence. Stirring your beer means introducing it to the air as well as additional tools so future aeration is typically not worth the risk.