Question about rehydrating yeast

[garym58]

Hello all

I have been using those kits to brew beer and have a question about the yeast that comes in it. When it came time to pitch the yeast I read the instructions on yeast package that said to rehydrate it. After I put the yeast into warm water to rehydrate it I read on the kit instructions not to rehydrate and just put straight into the wort. The yeast had only been in the water for a few minutes so I just dumped it into the wort. Will this ruin the beer?

Gary

 

[McGarnigle]

Re-hydrating won't ruin anything unless you did it wrong (e.g., used water hot enough to kill the yeast).

The consensus view seems to be to re-hydrate, even though some sources say don't bother, it's unnecessary. I would trust the yeast packaging over kit instructions, but no big deal either way.

 

[unionrdr]

Rehydrating yeast in about 400mL of warm 80-90F water for 30 minutes or so helps hydrate the dry yeast. When pitched at within 10 degrees of wort temp, it can cut lag time before visible fermentation begins.

 

[mabrungard]

As unionrdr points out, rehydrating is helpful. I've performed trials with US-05 and have confirmed to myself that rehydrating the yeast with pre-boiled and cooled water does cut the lag time. While rehydrating is not required...it is desired.

 

[chezhed]

I rehydrate when my calculation for number of packets comes up to an odd number. ie, 3 packs for 10 gallons would require I weight out packages and split, which for some reason I don't like to do. So I just rehydrate the 3 and then pour equal volumes from my graduated measuring cup into each fermenter.

I don't do it to cut lag time...just for convenience I guess. Lag time is just patience

 

[dkevinb]

I figure the yeast manufacturers know how to treat their own yeast, so I follow the instructions on the back of the package to rehydrate. Many of them also say you can sprinkle dry, basically using the wort to rehydrate, but studies show you get more and healthier yeast cells and reduced lag time if you rehydrate first. I always rehydrate in boiled/cooled water, then pitch into the chilled wort. I always get airlock activity in less than 24 hours, meaning it's working when I wake up the next day. I figure it doesn't add any additional time to my brew day, it's easy to do, and it increases the odds of a successful fermentation, so why would I not rehydrate?

 

[andy6026]

What you do before pitching the yeast all comes down to the number of healthy yeast cells that you need to pitch in order to get good beer. However, I find that there's a good rule of thumb to exercise without doing a pile of number crunching or even consulting an online calculator.

1) Dry yeast CAN be simply opened up and sprinkled onto the wort and you'll likely get good beer. However, re-hydrating the yeast will give you greater numbers of healthy yeast going to work in the fermenter. I always re-hydrate my dry-yeast. Others would say it's unnecessary.

2) Liquid yeasts CAN be simply poured into the fermenter and you'll likely get good beer. However, making a yeast starter to multiply the yeast before pitching will give you greater numbers of healthy yeast cells to go to work on the beer. I almost always make a starter with liquid yeasts (Wyeast and White Labs). Stir plates aren't necessary, but again, you'll get higher numbers of healthy yeasts if you use one.

I'd say rehydrate with dry yeasts if you are able to without too much inconvenience, and make starters with liquid yeasts if you are able to.

 

[mabrungard]

I figure the yeast manufacturers know how to treat their own yeast, so I follow the instructions on the back of the package to rehydrate.

That is a good thought. However, even a dry yeast manufacturer knows that there are hazards with having their customer perform another step in using their yeast and either killing or contaminating their product. So, some manufacturers avoid mentioning the water rehydration step out of their fear that we aren't smart enough to execute that step properly.

If you spoke to the yeast biologists directly from those manufacturers that advocate pitching dry yeast directly into wort, they would confirm that rehydrating the yeast in water reduces the osmotic stress on the dry cells and produces the highest yeast viability (thus the shorter lag time due to the higher yeast population).

Those that are unsure about their ability to properly rehydrate yeast in water should probably just pitch the dry yeast directly into the wort. Those that have the skill and patience might consider the proper rehydration since there is a known benefit.