Can I store plate stirred yeast in the fridge and pitch a week later?

[cannman]

Friends and I want to brew using the same yeast strain. This will be a 30 gallon brew or six 5-gallon batches all made on the same day. Creating yeast for this project will take days using 1 stir plate and a 5000ml Erlenmeyer flask. If I store 1 gallon of fresh starter in the fridge while the next batch stirs up, can I directly pitch this come brew day say a week later? Is there a better process?

 

[Conehead]

I do it all the time. I make my starter a little bigger though just to be sure. At the moment I have some yeast that is getting near 4 months old. I am making a big starter and storing it in the fridge for a week or so. I think if you plan on storing for a longer period you should decant the wort and top up with boiled and cooled DI water.

 

[masonsjax]

Yes that's a good plan. If you're storing long term, dont replace the wort with water. Wort is a far better storage medium for several reasons. You can however replace the wort with fresh unfermented wort every 4-6 months and that will keep the culture healthy. When you're ready to use it again, make a starter if it's been more than a few weeks.

 

[WoodlandBrew]

Yes, Viability should still be high (about 90%) but vitality may be a little low. Glycogen get depleted very quickly in the refrigerator. You can expect a lag time of about 12-18 hours. It should perform similar to yeast from a vial.

 

[cannman]

Thank you for your replies

I do it all the time. I make my starter a little bigger though just to be sure. At the moment I have some yeast that is getting near 4 months old. I am making a big starter and storing it in the fridge for a week or so. I think if you plan on storing for a longer period you should decant the wort and top up with boiled and cooled DI water.

Thanks for the input. I was wondering what water would do for the starter that just leaving the boiled old wart wouldn't? I don't have an answer, but if I don't ask the questions, I won't be able to sleep

Yes that's a good plan. If you're storing long term, dont replace the wort with water. Wort is a far better storage medium for several reasons. You can however replace the wort with fresh unfermented wort every 4-6 months and that will keep the culture healthy. When you're ready to use it again, make a starter if it's been more than a few weeks.

Ahh More water speak! :rockin:

I keep slants for future propagation where I can keep track of colonies and actually see contamination. I'd hate to have brew-day planned and when I reach for the starter I find it rotted away with last Thanksgiving's green bean casserole. But it is comforting to know that if I do keep gallons of starter for more than a week that it will keep. Thank you.

Yes, Viability should still be high (about 90%) but vitality may be a little low. Glycogen get depleted very quickly in the refrigerator. You can expect a lag time of about 12-18 hours. It should perform similar to yeast from a vial.

Based on your comment of vitality and the refrigerator, would you recommend a different method of keeps for the week of storage? :beard:

 

[masonsjax]

You could keep it at room temp and feed it a little sugar (DME) each day to keep it from going dormant.

 

[WoodlandBrew]

Storage for a few weeks, maybe a couple of months I would recommend the refrigerator. Storage for a year or more I would recommend freezing with 10% glycerin.

I'm working on a comparative storage experiment. Once I have the data I'll be able to draw a more defined line between the storage methods.

 

[trentm]

Yes, Viability should still be high (about 90%) but vitality may be a little low. Glycogen get depleted very quickly in the refrigerator. You can expect a lag time of about 12-18 hours. It should perform similar to yeast from a vial.

I really like what Woodlandbrew is saying about vitality. Although yeast can remain viable (alive) for several weeks in cold storage, the vitality (health or the ability to ferment) can be compromised in about 1 week. The intracellular glycogen (and other carbohydrates) content can become low. The yeast is using it to stay alive. But we count on these carbohydrate reserves for the yeast to use as energy during lag phase to synthesize sterols in order to form healthy cell membranes and walls, leading to strong, healthy, complete fermentations. It is for this reason most commercial breweries will not store yeast more than 1 week. But as homebrewers we have an alternative. When yeast is subjected to a starter (actually any fermentation) it rebuilds it's carbohydrate reserves. This happens at the end of fermentation. So, if yeast is stored for more than 1 week, it may be a good idea to subject it to a starter and allow the starter to go to completion and maybe let it rest at fermentation temp for a few hours after apparent completion.

 

[AnOldUR]

I'd time a 10 gallon batch and direct pitch from the slurry. Why make starters when you can have beer?

 

[WoodlandBrew]

In my experience, low glycogen content (low vitality) leads to a longer lag time, but does not impact the yeasts ability to ferment. My understanding is that the lag time is longer because the yeast do not have glycogen to aid in sterol production. However once the yeast have prepared their cell membranes for fermentation they preform just as well as yeast that started with a glycogen reserve.

See here:
http://www.wyeastlab.com/com-yeast-storage.cfm

 

[trentm]

In my experience, low glycogen content (low vitality) leads to a longer lag time, but does not impact the yeasts ability to ferment. My understanding is that the lag time is longer because the yeast do not have glycogen to aid in sterol production. However once the yeast have prepared their cell membranes for fermentation they preform just as well as yeast that started with a glycogen reserve.

See here:
http://www.wyeastlab.com/com-yeast-storage.cfm

That's an interesting read but I don't see a reference to "performing just as well". This did however jump out as the take home message to me: "The cells glycogen content indirectly affects the cells ability to uptake nutrients and perform a healthy fermentation." I truly believe that poor vitality is at the foundation of poor attenuation and stuck fermentations that are the bane of the homebrewer. The sterols that yeast synthesize at the beginning of fermentation using energy supplied by stored carbohydrates, oxygen supplied by us, and fatty acids supplied by the wort are shared with each new daughter cell. So as yeast reproduce in the absence of oxygen (after our initial dose of oxygen), the amount of sterols are depleted with each new cell and the cell walls become leathery making it incapable of budding at some point. In addition sterols keep the cell wall elastic and fluid allowing the transport system into and out of the cell to operate. When the cell walls become leathery late in the fermentation, the transport systems do not allow sugar into the cell and alcohol to move out of the cell. Alcohol builds up to the point that it becomes toxic and the cell eventually dies. With this in mind we may also assume that yeast that have gone through a healthy fermentation maintaining fluid, flexible cell walls are more fit to survive a storage period. Now glycogen is not the only factor, oxygen and fatty acids are the main ingredients in synthesizing sterols. But oxygen is only available during the lag phase, it is all used up by the time reproduction begins and we should be very leery about adding more at that point. Therefore, during lag phase is the only chance yeast has to produce sterols, while the main energy source to accomplish this is stored glycogen.

I don't mean to say that poor yeast vitality will inevitably lead to poor attenuation or a stuck fermentation but it may. Chris White is often quoted as saying "Yeasts can make over 500 flavor and aroma compounds” and as we know not all of these are a benefit to beer. In order to consistently bring out the ones we want and exclude the others, I believe healthy yeast is the key.

Some of the above is paraphrased from:http://www.lallemandyeast.com/articles/yeast-multiplication

 

[WoodlandBrew]

Use of glycogen to synthetises sterols is prefered by the yeast, but absence of glycogen does not mean that sterols are not synthesized. If there is no stored glycogen then the yeast will created it from wort constitutes. This occurs much slower with poor cell permeability, but eventually the cells will create the sterols needed and be healthy. This accounts for the extended lag. The limiting reagent in sterol production in fermentation is generally oxygen in a normal fermentation, not glycogen.

See Dr. George Fix "Principles of Brewing Science" chapter on "The Initial Period"

If you are interested in what "my experience" is then see my blog here:
http://www.woodlandbrew.com/search?q=side+by+side+starters