Discussion in 'Grain, Hops, Yeast & Water' started by treebeard, May 16, 2018.
An interesting development? I'm not wholly convinced. What would you do?
The adding dry yeast direct sounds right to me, I have never heard anyone claim anything else has added benefit. As for the aeration I don't know, you need enough oxygen in the wort I assume but extra with a little wild yeast I have no idea, also I assume his conclusion is for dried yeast and results may change if using liquid yeast.
It seems to suggest the research shows there is no benefit to either hydrating the dry yeast or oxygenating the wort. Indeed, that it has a detrimental effect on yeast health.
Surprised about the rehydration, it has always been thought that wort puts more stress on the dry yeast than water.
My understanding was the way pouring dried yeast over the top and not stirring allowed it to slowly soak into the wort avoiding excess stress.
Yes me too!
From what I understand, the stress was also caused by the sweet wort being a thicker liquid which put more stress on the yeast that the water. I can't think of anything else I would re-hydrate with other than water, due to that what is the component removed during the hydrating process.
Still it's only one lot of results from one yeast manufacturer, even David Heath has said he is not going to stop aerating his wort yet.
I think the research also said, not aerating the wort does cause a lag before the yeast gets going, I would rather the yeast gets a good grip before any other wild nasties have a chance. So I shall continue to aerate!
Christ. I can't draw any conclusions cos that guy sounds so dull and boring that I nodded off after a minute. Most likely hair-splitting cobblers anyway.
I'm surprised about both of these results. My understanding as far as rehydration goes is that when dry yeast is added to the fluid, be it water or wort, it takes a few minutes for the cell walls to rehydrate and establish themselves as an effective barrier to whatever is in the fluid. If you add them to wort the cells can be overwhelmed by the high concentrations of sugars. Figures I've seen suggest that up to half of the yeast could be killed doing this. I don't usually use dried yeast but I think that if I was fermenting anything other than a standard gravity beer I would probably continue to rehydrate. I know a lot of people don't bother and get fine results so maybe it isn't an issue at standard gravities.
On oxygenation, I find this very hard to believe, unless they are specifically talking about dry yeast, in which case I have heard people say this before. The oxygen is required to synthesise sterols used in the cell membranes. Without sufficient oxygen, the yeast cells are not able to divide and multiply as they should and this results in lower attenuation.
I have heard people say that due to the manufacturing process, dry yeast has all the sterols they need for a healthy fermentation. If that's the case then that's fine and extra aeration might not be necessary. This might not be the case for liquid yeast, especially if pitched directly without being grown in a starter.
The other thing to bear in mind is that at the moment we are going on the second-hand account via a sales rep at a conference. I would love to see the published research that this is based on and I hope that they will publish the results so that they can be scrutinised by the scientific community and set against the body of evidence that suggests different results.
Finally, there is a difference between yeast health and characteristics that we might want in a beer. I'm sure the results will be linked but I thought there was pretty good evidence that appropriate wort aeration at the beginning of fermentation led to lower finishing gravities, for instance. They didn't say whether they were just measuring yeast viability, or the ability to fully attenuate a wort.
Didn't get far into it either. Most of the info is probably from a recent Fermentis talk and pertains to their dry yeast. The full report is due to be released in about 3 months time apparently.
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After all these decades of homebrewing, you'd have thought that the definitive answers would have been nailed through experience, a long time ago. What'll happen is, a weighty tome of equations and algebra will be produced, to the benefit of no-one and the befuddlement of many a hapless homebrewer. Just chuck the stuff in and let it do what it wants!
Regarding the aeration thing, Braukaiser did some experiments about 5 years ago showing that greater access to air during the growth stage leads to more growth but slower fermentation and lower attenuation, so this isn't really groundbreaking research.
Interesting, I've always rehydrated dried yeast, as that's what it recommended on the packet. I don't actually aerate the wort at all (apart from when transferred from the Grainfather).
Whilst I do like David Heath's videos as they're very informative, his voice can be a bit sleep inducing at times
ya pipped me there pal....
his voice is bloody annoying...ive actualy fell asleep we one of his vids..
but hes a clever lad n stuff.
Helllooooo! and welcome to the video!....................and SLEEP!
Really, I've not come across that one. In the Yeast book by Chris White and Jamil Zainasheff, they argued quite strongly that lack of oxygen at pitching was a major cause for under attenuation.
The problem with brewing is that there is a lot of contradictory information out there. You just have to figure out for yourself what's important and who's worth listening to.
I agree about Mr Heath I do watch his vids even though I think he talks in a condescending manner especially if you are not a grain father owner
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