Reusing Yeast after Fermenation

It is possible to reuse the yeast several time. Ted Palmer advises :
    You can "re-pitch" yeast more than 10 times in most cases, the biggest factor in determining if the yeast is still healthy would be its viability. Viability is the percentage of live cells in a given sample. To test for this you will need a microscope, a hemocytometer and some methylene blue stain. Here is a good link written by a friend of mine that explains this method in detail
    http://www.brewingtechniques.com/library/backissues/issue2.4/allen.html

    Another important factor is the genetic strength of the yeast, some yeasts are very stable genetically others aren't. What this means is that genetic mutations change the profile of the cells to the point that they no longer resemble the parent strain. Some yeast strains mutate in less than 4 generations where others are stable for hundreds. Turbo yeast being a highly hybridized yeast falls into the former, I can't tell you how well it will perform or for how many generations, you will have to figure that one out on your own through experimentation. Many packaged yeasts are mixtures of 2, 3 even 4 different yeasts, so if one doesn't crop yeast at the right moment during a ferment one or more of the strains could wind up missing in action. Also be aware that the pitching rate or the number of cells added per ml is an important factor in any ferment . The right # is 10 X 10^6 cells per ml up to 12 degree Plato and you must add 1 x 10^6 per degree Plato above 12. That can be allot of yeast in a high gravity wort. The caveat in yeast pitching is more is better than less.
See also The Microbrewery Laboratory Manual: Jack comments ....
    I've been doing some fermentation speed/alcohol-sugar tolerance experiments. The Canadian wine yeast called Lalvin EC-1118 (champagne-saccharomyces bayanus), when pitched at a massive rate (I made up a starter of 10 lbs of sugar, 5 teaspoons of yeast nutrient, in 5 gal of water, then when this was done fermenting, I repitched the thick yeast cake at the bottom of the carboy into only 2.5 gallons of 15% potential alcohol sugar water), with what seems like excessive yeast nutrients, it acted the same as the Turbo yeasts I hear you guys in NZ talk about, plus, with the competative factor (it's a "killer" yeast strain) no boiling or campden tablets had to be used. Anyone who can't get a turbo yeast can make one by "overpitching " this wine yeast! Fun experiment, but I tested every wine yeast in the store, and I went through over 120 lbs of sugar. EC-1118 was the clear winner by a long shot. Hope this can help someone. (by the way, fermentation took less than a week)
David Lamotte writes (to CraftBrewing@egroups.com (a brewing group for Australians/Kiwis at YahooGroups)) ...
    Now repitching is a great way to get huge amounts of yeast working for you quickly, but you can also get the same amount of bugs doing nasty things. Bacteria grow much more quickly than yeast, but are usually killed off as the yeast get going making alcohol and lowering the pH (both are kryptonite to bacteria). But the few that survive from the first brew quickly grow to millions in the second and trillions in the third .... So it can often take a few batches before you have to dump one down the drain.

    You can just save some of the slurry from the bottom of the fermenter, but it can only be repitched a few times as the 'gunk' builds up and coats the yeast. The information that you were looking for comes from Wyeast's home page (http://wyeastlab.com/hbrew/hbyewash.htm) and tells you how to wash and store your slurry. You can replace the plain water with an Acid wash which will kill any bacteria (but not wild yeast).
Donald advises ...
    For yeast re-pitching & yeast washing applications the alcohol should not go above 6%. This is so the yeast will not become stressed and start to reproduce sexually (causing off flavors & mutations) rather than asexually.

    Please note that at the end of primary fermentation there is enough yeast for four re-pitches. So, one can harvest 1/4 for re-pitch unstressed yeast before stepping up with the remaining 3/4. Also if you want to change your yeast strain by harvesting: Repitch of the bottom 1/3 will be more flocculent, repitch of the middle will be moderate 1/3 and re-pitch of the top 1/3 will be hardley flocculent. It is suggested to take 1/3 top, 1/3 middle & 1/3 bottom to assure yeast character. What you want the yeast to do now is up to you.
Turbo yeasts are not recommended to be reused. Mike explains "ul> You can easily re-use beer yeast for two reasons - beer generally is not fermented to high alcohol levels, so most of the yeast in the cake at the bottom is still alive, and beer wort is a nearly perfect growth medium to make more new yeast cells.

Turbos are designed with a LOT of live yeast cells and enough nutrients to grow more - but by the end of a fermentation, the nutrients (should be)nearly all gone, and most of the yeast in the cake is dead - from the combined effects of heat and high alcohol levels.

If you pitched a new sugar wash onto a turbo yeast cake, I would expect it to ferment - but MUCH more slowly than when the turbo was new, and would not expect it to reach the same alcohol levels.
Jack divulges his method for preserving yeast cultures...
    Most home brew shops sell syringes (about 10cc sizes) without needles- these can be used to collect yeast in a perfectly clean manner. Fill up a measuring cup full of hot water and microwave it until it's boiling, then stick the tip of the syringe into the water and fill the syringe totally with boiling water, wait one minute, then repeat twice more with boiling water. On the last draw-up of the boiling water, instead of squirting it out, leave it in the syringe, put the cap on and allow the syringe/water to cool in a draft free place. When you brew your next batch of whatever, pour off all of the beer/wine/mash until you just have the yeast layer covered with liquid (the yeast layer sould never have been exposed to open air). Un cap the syringe and wipe down the tip with alcohol, then stick it under the surface of the fermented liquid near what looks like a healthy yeast colony, squirt out the water into the general area to stir the yeast up a little bit (don't wash it away, just unpack it from it's settled state- squirt the rest of the water away from the yeast you are aiming for to prevent from scattering it to the wind-the amount of water needed to blast the yeast loose depends on what kind of settling properties it has)- then draw back the syringe plunger to collect the 10cc of yeast slurry. The inside of the syringe has not been exposed to the contaminating air, neither has the yeast (due to the protective blanket of beer/wine/mash that you did not pour off), using standard beer "yeast starter" techniques you can use the syringe to make ten "sub-cultures" (about 50 to 100ml), which can then be used to make a one litre starter for your next batch- This technique will not work well for the Turbo yeasts designed for nothing but sugar- but for expensive (liquid) yeast cultures for fancy styles of beer/ wine/ whiskey mash- this system works wonders - I store my syringes in the 'fridge- no acid washing no HEPA filter no extra food- they last at least a month this way. Just make sure that if your mom house-sits for you while your on holiday, that you show her what they are so she doesn't think your a junkie and pours your trappist ale culture down the toilet. By the way- special blends of various beer and bread yeasts work great for fermenting whiskey mashes.

    Magnetic Stirrers

    You can make a magnetic stirrir out of an old tape player- epoxy a bar magnet to the spindle that turns when you push play and fast forward, mount a piece of thin aluminum above it, buy the stir bars at a science shop, or make one by sealing another bar magnet in a length of tubing cut out of the stem inside a Windex spray bottle, then seal it with the hot edge of a knife- very handy for yeast propagation


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