Fermentis just put out a very informative and detailed study they conducted on a few of their strains where rehydration vs direct pitch was tested. It also included different ways to rehydrate to test viability and performance vs direct pitching. There has been a lot of talk recently about this topic as it always seems to come up. For quite some time now we have been more comfortable recommending that aeration is not needed and also that direct pitching seems to work just as good and there is no need for rehydration. Well, for those that like the scientific side of things over the general word of mouth or because so and so on the forum said so or someone got secret squirrel information in an email…here ya go.
I haven’t seen this mentioned or pop up so if it’s already posted, delete it.
edit: this is INCREDIBLE information on testing. this is great so far. wow. temp barely matters, time of rehydration barely matters, without agitation produced better results than mixing or agitation.
ok, and well it looks like there is basically no difference in results in almost any way between direct pitch and rehydration. also very little loss of vitality between fresh yeast and “artifically aged for 3 years” yeast in their study.
dry yeast, at least produced by fermentis, is really hardy stuff.
Not all of the information that was covered in the webinar is included in the pamphlet. I was finally glad to see someone backing up what I have said for years about the impact of shear stress on viability in stirred cultures. Most people poo-pooed me on that claim because they were worshiping at the alter of Kai Troester, which stated that stirred cultures produced more cells. Stirred cultures produce more cells because shear stress from the stir bar kills more cells. The only cell count that matters is the viable cell count. Yeast cells reproduce for replacement only after maximum cell density has been reached. If there is no carbon source for the creation of replacement cells, the viable cell count actually goes down.
Thanks for the quick summary. I am not at all surprised. In my own homebrewery, experience has demonstrated many dozens of times all of these truths. Which are part of the reasons why I tend to use dried yeasts almost all the time now and have for several years. If we could eventually obtain great dried yeasts for every style… well I believe I would! Things are getting better every year, closer and closer, that’s for sure.
True but some of the same graphs and information was in there. Likewise not all of the information in the pamphlet was covered in the webinar. Both are good resources for the subject.
Do you think US-05 has slowly drifted from the liquid versions or was always peachy? I used to use it a lot the 2010-2015 time frame. I don’t remember the peach but I was new to brewing so I might not have noticed.
Of course. I’ve spent a fair amount of time with homebrewers in South America and dry yeast is 98% of what they can get and use. I should have said something to the effect of “don’t necessarily expect any dry yeast to be a lot like the liquid “equivalent””.
