I’ve been messing around with brewing mead and wine recently in addition to my beer brewing activities. It’s a veritable 24 hour brewing circus around my house with any free minute filled with fermentation of some kind. At the moment my living room smells like a fermentation room at a winery. Stephanie loves that kind of thing.
Anyway, wine and mead makers tend to use dry yeast as opposed to beer makers who tend towards liquid yeast. Older style beer kits that come in a can still include a packet of dry yeast (or so I’ve been told, I’ve never actually made one), but most contemporary recipes call for liquid yeast from Wyeast or White Labs. From what I can tell, most serious brewers are using liquid yeast and making starters to pitch into their wort in order to get a proper yeast cell count for a clean fermentation. There are a few yeast pitching rate calculators out there from Wyeast and from Jamil and some well read articles that serve as the guidelines for making and using starters.
Standard brewing practice also involves either shaking the crap out of the carboy to aerate the wort or using an oxygen tank and diffusion stone to dissolve pure oxygen into the wort. Yeast use oxygen to make lipids/sterols for their cell membranes. Healthy cell walls allow for better yeast growth and propagation, better uptake of nutrients, and better alcohol tolerance. Healthier yeast means cleaner fermentations and fewer off flavors in the final beer. There has been a interesting series of posts from Mike Flaminio on wort oxygenation on the Homebrew Beer Blog recently as well. The aim there being consistent, proper wort oxygenation as opposed to the blind process most of us follow that apparently leads to inconsistent over oxygenation. There has also been a long thread on the Brew Board about using very small amounts of olive oil in the wort instead of oxygenating it. Yeast apparently can uses the olive oil to synthesize the lipids/sterols they needs for their cell walls.
Wine kits just ask the wine maker to sprinkle a packet of dry yeast on top of the must to start fermentation. Some wine makers rehydrate their yeast prior to pitching, usually in Go-Ferm. There seems to be some debate in the wine making community about which practice is preferable, with a larger number of people taking the wine kit makers advice (from my limited reading and experience). According to Tim Vandergrift at WinExpert, the leading wine kit manufacturer:
“The real scoop on why kit companies don’t ask you to rehydrate: It doesn’t make any difference.
In the 6 US gallon (23 litre) volume, the 5-gram packet of yeast provided will ensure a quick and thorough fermentation with a quick sprinkling and nothing else.
It is technically true that re-hydrating gives higher viable cell counts–but only if you do it with perfect precision and accuracy. While there are a couple of pitfalls, the commonest one is temperature shear.
Since you have to rehydrate at 100F, in ten times the weight of the yeast in pure water, the yeast slurry will be fairly warm. If you pitch this re-hydrated mass into a must of 64F, the shock of the wildly disparate temperatures will kill a lot of those previously viable yeast.
In tens of thousands of trials, we’ve never seen anything approaching sub-optimal times for culture strength and subsequent fermentation.”
In either case, there are no starters and no oxygenation occurring, though wine makers do sometimes stir their must and/or leave the fermentation chamber relatively open compared to brewers in order to get more oxygen dissolved. These are some pretty divergent practices, so I’d like to know how or why this is the case.
I found a response to questions about starters and oxygenations from Dr. Clayton Cone at Danstar/Lalleland/Lalvin, a leading manufacturer of dry yeast, that I found pretty interesting. Basically he says that dry yeast come packed with the amount of lipids needed to triple the yeast cell count. After those lipids have been used up, additional oxygenation is required for healthy cell growth. For brewing a 5 gallon beer between 3% and 5% alcohol, no additional yeast or oxygen are needed apart from what is available in a single 11g packet. For higher alcohol content beer, you either need to pitch additional yeast or oxygenate to allow for yeast growth. I’m not sure what Danstar considers a proper pitching rate, so that is something I will have to investigate. I do know that Jamil recommends pitching about 10g of yeast on average for an average gravity 5 gallon batch in Brewing Classic Styles. [Edited per Jamil's comment. Thanks Jamil. And as Jamil notes, batch size, OG, and yeast type are all variable inputs in the proper pitching rate - use his calculator to get precise amounts- I do.]
As a brewer, I’d prefer a higher pitching rate for higher alcohol beers so that propagation was mostly complete at pitching instead of trying to grow the yeast in the wort. That way the yeast can spend their time fermenting while in my wort instead of growing.
Dr. Cone mentions that Danstar grows their yeast along a different metabolic pathway than the one used by brewers that uses basically no sugar. Yeast propagated this way create very little alcohol. I assume this is done because it allows for more efficient healthy yeast production. When growing yeast in a starter, “no matter how much air you feed the fermentation, alcohol + CO2 are the main by-products. Your starter culture will have a much higher level of sugar [than the culture used by Danstar]. You will produce some cell mass but mostly alcohol and CO2 no matter how much air you add by stirrer or bubbles.” So starters increase cell counts but not in a way that is as effective as the propagation method used by Danstar. I guess that this also means that yeast grown in a starter, even under ideal conditions for a starter, is of a smaller amount and of potentially of lower quality due to the presence of alcohol and other less than ideal conditions.
So I guess my question is whether making a starter is an effective way to increase yeast cell counts prior to pitching or if instead it’s just a way to get yeast into active fermentation prior to pitching. Perhaps they generally make alcohol and CO2 and that starters are not the ideal environment for propagation even with the proper amount of oxygen. Buying 2 vials of White Labs yeast or 2 Wyeast Smack Packs is prohibitively expensive, especially given the increased cost of malt and hops. So I understand why people look for ways to grow their own yeast. But dry yeast is relatively inexpensive and prepackaged with the lipids necessary for healthy propagation and fermentation. Pitching a packet of dry yeast that cost less than $2.00 is definitely cheaper than pitching a starter made from DME, yeast nutrient, and a $6+ liquid yeast product – and that doesn’t count in the cost of the equipment needed to make starters (flasks, stir plates, etc.) or the time involved. If the metabolic pathways used by yeast from a starter for propagation produce lower quality yeast than the yeast from dry packets, that makes using dry yeast even more appealing. And if re-hydrating dry yeast generally makes no difference, all the better.
Of course liquid yeast manufacturers make a far wider variety of yeasts than are available as dry yeasts, so sometimes your options are limited.
I’ve never used a dry brewer’s yeast, so this is all just speculation at this point. I’m planning on trying out some dry yeast and comparing the results to equivalent liquid yeast from starters. I ordered 12 packets of dry yeast, 2 each of 6 different varieties, from Williams Brewing mostly because they are having a sale on dry yeast – 25 cents off each packet of dry yeast when you buy 12 or more. We’ll see what happens, but I am hopeful that I’ll get good results. If dry yeast is a reasonable or better alternative to liquid yeast and starters, maybe more people will start using dry yeast and more varieties will be made available. Or it might suck and I’ll go back to liquid yeast starters.