Boiling Beer: Yeast Removal Or Flavor Sacrifice?

Adding near-boiling water to fermenting wort can kill some of the yeast, especially those in contact with the boiling water. However, if there's enough yeast in the fermenter, distributed throughout the beer, a lot of it may still be alive. Monitoring the temperature is crucial to avoid overheating the yeast, and if it survives, you can re-activate it by adding more DME, sugar, or honey in a solution of boiled water.

Boiling water can kill yeast during the fermentation process

Adding near-boiling water to fermenting wort can kill some of the yeast, at least any yeast that comes in contact with the near-boiling water. If there was enough yeast in the fermenter, distributed in other parts of the beer, then a lot of it may still be alive.

When raising the temperature of the fermenting beer, you want to do it slowly to avoid shocking the yeast. Adding boiling water is not the best way to do this. Instead, try moving the fermenter to a warmer area, or use a brew belt to gently bring up the temperature. Sometimes, just adding an insulating layer (and an old blanket, for example), is enough. The fermentation process produces heat, so if you can prevent that heat from escaping, the temperature will rise.

When using yeast in your dough products, you should know it will instantly die if your water temperature for mixing goes above 140 degrees Fahrenheit. You may notice some recipes which call for rapid and instant rise yeast products to use heat from 120 to 130 degrees Fahrenheit. These temperatures have to be carefully monitored, and you need to know your thermometer is accurate because you cannot go over 140 degrees unless you intend to kill the yeast. Some manufacturers of recipes claim their reasoning behind suggesting the hotter water temps for mixing the yeast is to ‘guarantee’ its activity of it.

Boiled water does not contain oxygen, and in this case, that’s a good thing. We want to avoid exposing the yeast to dissolved oxygen. Oxygen would cause the yeast to deplete their glycogen reserves and you’d have no viable yeast to pitch in your next brew. Which is just a fancy way of saying that by depriving yeast of oxygen, they stay dormant. So long as it’s in the fridge, you can store it for a month or two. You’ll know it’s time to throw it out when it turns brown like peanut butter.

Adding boiling water to fermenting wort can kill yeast that come in contact with it

Boiled water does not contain oxygen, and in this case, that’s a good thing. We want to avoid exposing the yeast to dissolved oxygen. Oxygen would cause the yeast to deplete their glycogen reserves and you’d have no viable yeast to pitch in your next brew. Which is just a fancy way of saying that by depriving yeast of oxygen, they stay dormant. So long as it’s in the fridge, you can store it for a month or two. You’ll know it’s time to throw it out when it turns brown like peanut butter.

Blocking the sun is important to avoid skunking the beer, but you can still use the sun to heat it. With all these methods, the temp needs to be monitored so you don't overheat the yeast. Once it's warmed up, you can also add some more DME, sugar or honey in a solution of boiled water, cooled down first to help activate the yeast, or add more yeast.

Beer was getting cold so in a desperate attempt to raise the temperature I put near boiling water into the container. So 450ml into 23litres of beer. The beer had only been brewing for 4 days. Edit: I can confirm that the yeast survived. The gravity was originally 44 when I started and after the "boiling water" incident it was 22. It eventually ended up at 9. So I'm pretty sure it survived. Won't ever risk it again though.

Boiling water can kill yeast that come in contact with it

Adding near boiling water to fermenting wort can kill some of the yeast, at least, any yeast that comes in contact with that near boiling water. If there was enough yeast in the fermenter, distributed in other parts of the beer, then a lot of it may still be alive. If you see signs of fermentation (like bubbling airlock, krausen), it worked. If you don't, it still may be working but you'll need to check the gravity a few times to know if it's woken back up.

Boiled water does not contain oxygen (at least at the same levels of tap water), and in this case, that’s a good thing. We want to avoid exposing the yeast to dissolved oxygen. Oxygen would cause the yeast to deplete their glycogen reserves and you’d have no viable yeast to pitch in your next brew. Which is just a fancy way of saying that by depriving yeast of oxygen, they stay dormant.

Once it's warmed up, you can also add some more DME, sugar or honey in a solution of boiled water, cooled down first to help activate the yeast, or add more yeast.

In the future, you should not do this again. You can warm it up by other means, and generally, unless it has gotten very cold, you can wake the yeast up again.

Boiling water can kill yeast that come in contact with it

Adding boiling water to fermenting wort can kill some of the yeast, at least, any yeast that comes in contact with that near boiling water. If there was enough yeast in the fermenter, distributed in other parts of the beer, then a lot of it may still be alive. If you see signs of fermentation (like bubbling airlock, krausen), it worked. If you don't, it still may be working but you'll need to check the gravity a few times to know if it's woken back up.

The only microorganisms that survive are the bacteria that form protective spores, such as Clostridium botulinum. High acid levels are used to prevent the spore-formers, especially Clostridium botulinum, from growing. pH is the measurement of how acidic a food is. The lower the pH, the higher the acid content. When the pH is below 4.6, growth of spore-formers is inhibited.

If you have a branch of Wilko near you, would be worth a visit in an emergency. They stock basic home brew supplies, including yeast. That's what I did when this happened to me. I let the pouch in boiling water for probably 5 min only though. I made a pseudo-starter (just sugar and some clean water), not expecting any life left there, but when it started bubbling I used it and it worked! Apparently dry yeast can sustain heavy insults...

Boiling water can kill yeast that come in contact with it

Adding near-boiling water to fermenting wort can kill yeast, at least any yeast that come in contact with that near-boiling water. If there was enough yeast in the fermenter, distributed in other parts of the beer, then a lot of it may still be alive. If you see signs of fermentation (like bubbling airlock, krausen), it worked. If you don't, it still may be working but you'll need to check the gravity a few times to know if it's woken back up.

Boiled water does not contain oxygen, and in this case, that’s a good thing. We want to avoid exposing the yeast to dissolved oxygen. Oxygen would cause the yeast to deplete their glycogen reserves and you’d have no viable yeast to pitch in your next brew. Which is just a fancy way of saying that by depriving yeast of oxygen, they stay dormant.

Boiling water can kill yeast, but you can warm it up by other means, and generally, unless it has gotten very cold, you can wake the yeast up again.

Blocking the sun is important to avoid skunking the beer, but you can still use the sun to heat it. Monitoring the temperature is important to avoid overheating the yeast. Once it's warmed up, you can also add some more DME, sugar or honey in a solution of boiled water, cooled down first to help activate the yeast, or add more yeast.

Beer was getting cold so in a desperate attempt to raise the temperature I put near-boiling water into the container. The beer had only been brewing for 4 days. Edit: I can confirm that the yeast survived. The gravity was originally 44 when I started and after the "boiling water" incident it was 22. It eventually ended up at 9. So I'm pretty sure it survived. Won't ever risk it again though.

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