17 replies to this topic

[3rd party JKor]

I'm making my first batch of starter wort via mashing today. What's the consensus? 148-149?

[denny]

That's fine, but it really doesn't make much difference. I doubt that the DME most of us use was originally mashed that low. You're making yeast, not beer.

[zymot]

OK I see. You are going to mash your starter, with grains and sparge and all that. Interesting.....I would say 148-150 is where you want to be.Are you going to boil it to get some hot break action?I use a pressure cooker and can 5 gallons of starter at a time. I am a HUGE fan of servomyces. I throw in 1 or 2 capsuals. Money well spent, IMHO.zymot

[drewseslu]

Servo is the caddillac of yeast nutrient, but a bit of bakers' yeast added to boil will help, too.I would tend to mash low for a starter wort, just so that in the case of contamination there is less for the baddies to chew on and grow. But if you can keep it sterile enough, it won't matter.

[3rd party JKor]

Yes, I'm making ~8 gallons of wort for starters. ~3.5-4 gal for canning, ~3 gal. for a WLP830 starter and ~1 gal for a WY3068 starter. I'll boil it and add some yeast nutrient, whirlfloc, and hopefully leave behind some good break.It's much cheaper than extract obviously. The LHBS is selling DME for $5/lb, so it would cost me ~$35 to make 8 gals with DME. I paid $0.50/lb for my 2-row, so it will cost me ~$5.50 in ingredients.

Edited by JKoravos, 25 July 2009 - 10:27 AM.

[siouxbrewer]

I don't can anything (sigh) but I fill tupperware with boiled wort, freeze, then reboil for my starter. I use blended yeast nutrient and boil for 10-15 min. mashed at 148-150f but Denny's right, just making yeast not beer. I always use a fairly thin wort about 1.030 so the yeast plow through it quickly without stress or too much residual alcohol.

[Salsgebom]

fermentability only matters for fermentation, not aerobic yeast growth.

[denny]

Servo is the caddillac of yeast nutrient, but a bit of bakers' yeast added to boil will help, too.

Through the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?

[DaBearSox]

Through the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?

www.whitelabs.com/beer/Yeast_Nutrition_Article.pdfpage 3*doesn't touch on bakers yeast though just thier product

[denny]

www.whitelabs.com/beer/Yeast_Nutrition_Article.pdfpage 3*doesn't touch on bakers yeast though just thier product

And it doesn't really address using any kind of yeast as a nutrient, except when it's grown with the special nutrients they mention. So, throwing old brewing yeast in may or may not do anything.

[zymot]

Through the years, I have frequently heard references to adding yeast to the boil as a nutrient, but I've never heard an explanation of how or why it works. Can you provide one?

The hypothesis that I heard was tied together autolysis/yeast are cannibalistic and one yeast nutrient made of yeast hulls. So if you had some extra yeast, you could thow it in the boil as a homemade yeast nutrient. Unless you add a ridiculous amount, I cannot see any harm.IMHO: Commercial yeast nutrients are so cheap that if you need some boost to your wort, do it right and use a product that is designed to do the job.But then this is homebrewing, where saving are often not measured in pennies or dollars, but in percentage points.zymot

[3rd party JKor]

fermentability only matters for fermentation, not aerobic yeast growth.

The yeast are using the sugars in the wort for energy, correct? I would think that having more sugars that they can use for energy the more yeast growth there would be. Am I wrong here?

[Salsgebom]

The yeast are using the sugars in the wort for energy, correct? I would think that having more sugars that they can use for energy the more yeast growth there would be. Am I wrong here?

You are correct that they use glucose for energy, but their level of growth is dependent on oxygen in a starter. The amount of sugar they will use by the time they've consumed all the oxygen hardly makes a dent in your gravity. Now, if you've got a continuous aeration system, there is a point that you will need to add more sugars, but the difference between a 146F or a 156F fermentability I believe is negligible.

[3rd party JKor]

You are correct that they use glucose for energy, but their level of growth is dependent on oxygen in a starter. The amount of sugar they will use by the time they've consumed all the oxygen hardly makes a dent in your gravity. Now, if you've got a continuous aeration system, there is a point that you will need to add more sugars, but the difference between a 146F or a 156F fermentability I believe is negligible.

OK, I'm doing one as a stirplate starter and one as a simple starter. (don't mind the messy workbench, it's usually spotless )So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?

[Salsgebom]

So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?

Yes. This is not my strongest area. I have some nice diagrams of how the yeast cell transfers energy but they are at work. I'll see what I can find out when I am there tomorrow.

[BrewerGeorge]

I had the same thought as you, J. Last time I made a starter batch, I mashed the hell out of it - ramping up with the HERMS to hit ALL the stops. Ended up with a Bud Lite level of fermentability. Not sure if it helped or hurt, or made no difference.

[sam]

So, during aerobic growth they're not using much sugar, but during anaerobic growth they are using only sugar. I'm assuming the sugars they are using during aerobic growth are actually being used in a different pathway then the oxygen. Yes?

I think you've got the idea...Just to clarify... at least for us homebrewers, yeast will never respire aerobically. They will be in an aerobic environment but will always metabolize sugars via fermentation. The reason for this is the high concentration of sugars in the worts we pitch the yeast into. The yeast "sense" the sugar concentration and bypass aerobic respiration even though oxygen is available (a phenomenon known as the Crabtree Effect). They do take up oxygen molecules but they are not used for metabolism. Instead, the oxygen is used for sterol synthesis and cell wall maintenance/growth.Let's say you aerate your starter initially and then let it sit after pitching yeast. The yeast will initially consume the oxygen to prepare their cell walls. During this initial "lag", the yeast do not consume any sugars in the wort. All cell activity is powered by glycogen reserves within the cell. Once the cell wall is prepared, the yeast will begin fermenting the sugars and enter exponential growth. As the yeast use up the oxygen, their environment slowly moves from aerobic to anaerobic (I think this is what you were alluding to above). Any metabolizing of sugars was done only via fermentation.Now, let's say you continuously aerate your starter with a stirplate. This time, the yeast will always be in an aerobic environment. That is, there will always be oxygen available to the yeast. The yeast will take up oxygen to prepare their cell walls and then they will begin fermenting the sugars. Again, all metabolic activity is via fermentation only. This time, while the yeast is fermenting and growing exponentially, they can continue to take up more oxygen for cell wall growth and maintenance. This will result in larger cell counts in the starter.Sorry for the lecture... I just started typing and couldn't stop.

[3rd party JKor]

Well, geez, sam...nice first post!Welcome to the board and thanks for the insight into yeast growth.