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[cvdukes]

Anybody know what the fresh yeast are cultured in by the manufacturers?

The reason I ask is that I keep 5 different yeast cultures going for my winemaking. These were started from commercial packets (champange, sherry, etc.) and I haven't had to buy yeast in over 6 years. The culture media is simply diluted frozen orange juice with extra sugar added. These are kept in pint size plastic soda bottles fitted with fermentation locks. Every couple of months, I decant off the clear OJ (well fermented and quite drinkable!) and refresh the bottle with more mixture. If a yeast I use a lot of, I just decant and refresh more frequently, but I have let them go for 7-8 months without feeding them. The yeast grows like crazy in the media and accumulates in the bottom of the bottles... sometimes a couple of inches thick, especially if its a yeast that I don't use too frequently. Pouring a slug of the yeast into the raw wine "must" jump-starts the fermentation and overwhelms any native yeast if I don't get them all killed off with my sterilization process (since I can't use the chemical sterilizers). I've also thought about throwing in some of the wine yeasts into a bread, but I'm too new to the bread process to start this kind of experimentation.

It seems like this wouldn't be too hard to adapt to the bread yeasts. Maybe using some other culture rather than OJ... I know it would have to be slightly acidic for optimal results, but other than that it seems like growing your own yeast cake should be possible...

[dmun]

The extensive wikipedia article on yeast doesn't answer your question about the growing medium, but it does say that yeasts like a neutral ph growing medium. It's interesting that you are growing them in acidic orange juice. Maybe you could do an illustrated article on the process?

[KiwiPete]

Instead of a cultured fresh yeast, you can always use a wild yeast and culture it. I use the Camaldoli yeast from sourdo.com and love the added flavours in the crust.

(PS no connections with sourdo.com other than being a satisfied customer)

[cvdukes]

Originally Posted by dmun

...interesting that you are growing them in acidic orange juice. Maybe you could do an illustrated article on the process?

Not a whole lot to illustrate. Basically I just make up the frozen OJ (pulp-free) with about twice the water it calls for. Then I sweeten it with a high density syrup made by dissolving 5 pounds of table sugar in about 4 quarts of boiling water and allowed to cool. Normally I use about 1/2 as much of the sugar syrup as the diluted OJ. (Rest of the syrup goes into whatever carboy of wine I have that needs a little bump in the alcohol level...frowned on in the wine-making circles but preferred by the freinds that like the 17% or higher alcohol wine).

Attached shows one of the yeast cultures in a plastic water bottle fitted with a fermentation lock. Normally, the bottle is almost full with the OJ mixture, but I already poured off (and drank) the liquid. The yellowish cream at the bottom is almost 100% pure champange yeast... about 2/3 cup in this particular bottle. When I innoculate a wine, all of the yeast just gets poured into the wine must, then I replenish the bottle with fresh OJ mix. The residual yeast inside the bottle is enough to get it going again. I've even started one bottle by adding just a couple of grains of prepared yeast culture...since yeast can double something every 17 minutes in optimal conditions, it doesn't take long to get a large quantity. Limiting factor is amount of nutrient available to it. I believe the particular bottle pictured was last used a month ago, so you can see how much the yeast has mulitplied from just the little bit that stayed in the bottle.

Neutral pH may be better for yeast growth, but as I understand it, the lower pH keeps the yeast from committing hari kari if left unattended for long periods.
As I said before, it shouldn't be much a leap to adapt this to bread yeast if you really need a fresh growing yeast.

[dmun]

Thanks. That fermentation lock is a neat item.
Does this process happen at room temperature, or under refrigeration?

[cvdukes]

Its all room temperature... everything just stays on a shelf in the laundry room.

Oh, I popped over to the Wilkipedia link on the fermentation locks. Don't be put off by the claims that they are made of hand-blown glass. All of mine are molded plastic and were just a couple of bucks (if that much) at the local wine making store. I also have the three peice kind but much prefer the molded u-tubes.