Magnetic Stirrer/Yeast Starter Question

I've looked and so far, I haven't been able to find anything that could tell me how long to stir my yeast when making a starter. I just built a magnetic stirrer and plan on using it tonight to get a starter going for the weekend. Do I just turn it on and leave it running until I'm ready to pitch? Or do I need to turn it on for like 30 minutes, then leave it off for a few hours?

Also, what is the real advantage of decanting the liquid off of the top of the yeast prior to pitching? Some people do it, some don't. There doesn't seem to be any point.

you basically want to leave it on the whole time to keep the yeast in suspension. if you want to decant you will need to eventually shut it off to allow the yeast to settle.

decanting just eliminates any off flavors you might add to your beer by pouring the starter in. probably not as important with darker beers but a light brew might be affected more so. it seems most people look at it as personal preference. i don't see the trouble with decanting so i can't see why you would not do it.

When using a stirplate you tend to keep getting oxygen into the beer, so thus you end up with a pretty bad tasting starter, but plenty of healthy yeast.

I usually put my starter in the fridge the night before brewing and let the yeast settle out, then decant at the start of my brewday and let the yeast warm to room temperature, so they are close to the beer temp when I pitch.

Here's an awesome paper all about yeast propagation, It talks about using a magnetic stirrer for a yeast starter

MB Raines, Ph.D. - Guide to Yeast Culturing for Homebrewers - Maltose Falcons Home Brewing Society (Los Angeles Homebrewing)

scottfro said:

you basically want to leave it on the whole time to keep the yeast in suspension. if you want to decant you will need to eventually shut it off to allow the yeast to settle.

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I'm sure this question has been asked before and sorry for hijacking the thread but Is there a good method to Decanting? Just let everything settle and slowly pour off the liquid or use a syphon or some other method?

Thanks

burns629 said:

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I'm sure this question has been asked before and sorry for hijacking the thread but Is there a good method to Decanting? Just let everything settle and slowly pour off the liquid or use a syphon or some other method?

Thanks

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Just pour it off. I've tried everything from siphoning to using a turkey baster to try to get the starter beer off of the yeast without disturbing the yeast bed (this is after having it on a stir plate for a couple of days then overnight in the fridge to settle it out). I have to tell you, there is no better way to disturb the yeast bed than trying not to disturb the yeast bed. Just pour about 90% of the starter beer off and you'll be fine.

If you have an autopipettor with some 50 or 100 mL serological pipettes, that's another story. You could do it easily with that. But that's an expensive setup to have if you don't work in a biomedical research lab.

I'm wondering about the oxidation of the starter wort. By my understanding, the yeast uses up the O2 before the beer can become oxidized. Looking at it another way, the starter is pitched before oxidation has a chance to happen. Me thinks if oxidation was a concern in that short amount of time, it would also have a negative impact on the wort when it's aerated prior to pitching.

My thoughts on decanting is such that if one decants, one is getting rid of the really tenacious, less flocculating, higher attenuating examples.

I'm a new convert to the school of siphoning! Old threads be damned! It takes but a few drops of iodophor in a sauce pot of water to sanitize 2 feet of tubing! I can siphon off all the starter wort right down to the yeast line with no risk of losing yeast... try it, it's great, especially with yeast strains that don't floc into a dense pancake.

bigbeergeek said:

I'm a new convert to the school of siphoning! Old threads be damned! It takes but a few drops of iodophor in a sauce pot of water to sanitize 2 feet of tubing! I can siphon off all the starter wort right down to the yeast line with no risk of losing yeast... try it, it's great, especially with yeast strains that don't floc into a dense pancake.

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But if you want to swirl it up to dump it, it makes sense to leave a few ounces of starter wort in there to be able to mix up the yeast that is packed on the bottom. I make my starters in a growler and I leave about 1 cup of liquid behind so going to the trouble of siphoning doesn't make any sense to me IMO.
Another reason to decant that wasn't mentioned is that if you are making a decent gravity brew, why would you want to add a liter or two of 1.040 wort and dilute it down? Just plan ahead and make sure you have the time to cool it down and dump the old liquid.

bigbeergeek said:

I'm a new convert to the school of siphoning! Old threads be damned! It takes but a few drops of iodophor in a sauce pot of water to sanitize 2 feet of tubing! I can siphon off all the starter wort right down to the yeast line with no risk of losing yeast... try it, it's great, especially with yeast strains that don't floc into a dense pancake.

Click to expand...

I actually built a mini racking cane out of some leftover 1/4" copper tubing. I do leave a couple ounces in before I pitch to get the yeast back in suspension, but it works great for stepping up starters and getting as much spent wort out as possible.

I've heard Jamil say if the starter is more than 10% of his batch size he decants. I've just started decanting all of my yeast starters, at the very least it doesn't affect my volumes and measurements that way.

Oxidation is not an issue because you are going to be fermenting again. Any oxygen in the starter will be used up in the beer..