Reheydrating Fermentis dry yeast

[mark_g]

Just started using S-04 in the brewery and curious how others are rehydrating it. Ie are you using a stir plate or just using a spoon to stir it, should it be in a closed container or is an open one fine. Any other tips for using it would be great.

Thanks,

Mark

[billk]

I just add it directly to the fermentor as I am transfering in. I've been doing this for 8 years without an issue.

Bill

[ParishBrewingCo]

I second Bill's techique. I just add straight up to the cooled, oxygenated wort in the fermenter.

[kugeman]

Yup. I just sprinkle it over the top of the wort in the fermenter while I'm knocking out.

[Buckley]

I have rehydrated in a bucket stirring with a spoon and by adding it to the wort during knockout. I have only noticed a slight difference in lag time. I just add it during knockout to save the effort.

[Woolsocks]

We put a little sterile water in our fermenter, add the yeast, let it rest 15 minutes, then bubble oxygen through it to stir it up. Then let it rest 15 more minutes and begin knockout.

[nickfl]

I apparently have the most elaborate technique for dealing with dry yeast. I sanitize a 5 gal bucket and then run off 1/2 gal of boiling wort from the kettle into it. To that I add a couple of gallons of sterile water so that I hit a temperature of about 95F. I rehydrate the yeast in this liquid for about half an hour and then stir and add to the fermenter. This has worked well for me, but dry yeast doesn't really seem to care what you do to it.

[mark_g]

I have been reading Chris White's book on yeast, cleverly titled "Yeast". He says that by not rehydrating dry yeast you kill about half the cells pitched, which will affect the beer flavour. He says the high number of dead cells is due to the cells not being able to regulate what is going thru their membranes and they end up being killed by the high levels of sugar, nutrients and hop acids.

It sounds like most people are just directly pitching the dry yeast so are the flavours that Chris talks about not that bad? Are people pitching at a higher rate to make up for the large number of cells that are killed? Is Chris's view on dry yeast a little biased, seeing as he only sells liquid yeast?

Mark

[Buckley]

I have had tasting panel professionals from large breweries taste my brews as well as myself and have very seldom found those flavors. When I have it usually came down to a pitching ratio or re pitching issue. One thing to remember is that Chris White has a business to look after. His info while not incorrect may be skewed a tad. The best way to really get is to talk with providers of both liquid and dry yeast and do your own trials. (definitely up the pitch rate on lager stains.)

[Hazell]

I prefer to re-hydrate for 15 minutes in sterile water. I once had a winery consultant show me how he does it and that involved 40 Degree Celsius (~100 Fahrenheit) water for 15 minutes and it had the highest viability/vitality. I was always a little worried about being that hot so I do it at about 30 degrees Celcius (~85 Fahrenheit).

Doing a couple of trials yourself is probably the best way to go I think.

[a10t2]

In my own tests with US-05, I've found that rehydrating in wort reduces viability (as estimated using methylene blue) by about 40-60%, depending on OG. However, I also found that rehydration temperature has no significant effect on viability. I do concentrated boils, so all I do is sprinkle the dry yeast into the fermenter, then add my cold make-up water and let the flow of the water mix it. I then wait about 15 min before starting knockout.