Renewing The Yeast Cultures

[newguy]

All magnetic materials will lose their magnetism (it will actually be reset to 0) if heated above the Curie Temperature. This link lists the Curie Temperature of a few ferromagnetic materials down the right side of the page. To convert K to C, subtract 273 from the temperature in K. The warning for your stir bars may be because they're made out of a material with a low Curie point, or because the manufacturer is just trying to cover their ass. It probably has more to do with ass covering than anything else.

 

[Zwickel]

thats right Newguy, but the materials gets back again its magnetism as soon as the temp drops below the Curie temp.

Cheers :icon_cheers:

 

[newguy]

Zwickel, no they don't. What happens is that the magnetic domains within the material randomize at the Curie point. Unless the material is placed in a strong magnetic field as it cools, it's no more magnetic than an ordinary piece of iron. The randomization of the domains means that the net magnetization for the entire object is nearly zero because for every domain that points in one direction, chances are there is another somewhere that points in the opposite direction. The best you could hope for is that the bar would gain the magnetization of the earth's field, which isn't particularly strong, and chances are it would be at some odd angle to the bar instead of N at one end and S at the other.

The bar would still couple to a magnetic stir plate, but the coupling won't be as strong as for the original, unaltered, stir bar's field. This would translate into the bar losing coupling with the plate at a lower RPM than would otherwise be the case.

 

[Back Yard Brewer]

Zwickel, no they don't. What happens is that the magnetic domains within the material randomize at the Curie point. Unless the material is placed in a strong magnetic field as it cools, it's no more magnetic than an ordinary piece of iron. The randomization of the domains means that the net magnetization for the entire object is nearly zero because for every domain that points in one direction, chances are there is another somewhere that points in the opposite direction. The best you could hope for is that the bar would gain the magnetization of the earth's field, which isn't particularly strong, and chances are it would be at some odd angle to the bar instead of N at one end and S at the other.

The bar would still couple to a magnetic stir plate, but the coupling won't be as strong as for the original, unaltered, stir bar's field. This would translate into the bar losing coupling with the plate at a lower RPM than would otherwise be the case.

Way over my head h34r: :unsure: I think I will settle for a sterile spoon....

BYB

 

[Sprungmonkey]

I use a inoculation loop and just heat over the stove (or with some metho and a candle). Get the loop red hot and let it cool for about 5 secs before streaking.

 

[Hogan]

Im using steam for the cotton wool. Dont use any chemicals or alcohol for that, it will kill the yeast as well.


Cheers :icon_cheers:

Zwickel - After passing the cotton bud through the steam how long does it take the bud to cool down to a temp that won't kill the yeast cells when you dunk it in the inoculating yeast and then into the slant.

Cheers, Hoges.

 

[Hogan]

Re the above post.

I did some test runs using the kettle for steam and running the cotton bud across the spout for 15 seconds. Considering that steam temp would be in excess of 100c when it hits the bud, the tip of the bud cooled quite quickly.

I am also thinking that as I am using a flame source to clean the air in the vicinity of where the transfer from primary yeast source to slant takes place, then, if the transfer tube is sterile and the receiving slant is sterile and the cotton bud is sterile, then all slants could be inoculated without having to re-steam the cotton bud after every transfer.

Any thoughts please.

Cheers, Hoges.

 

[Franko]

Re the above post.

I did some test runs using the kettle for steam and running the cotton bud across the spout for 15 seconds. Considering that steam temp would be in excess of 100c when it hits the bud, the tip of the bud cooled quite quickly.

I am also thinking that as I am using a flame source to clean the air in the vicinity of where the transfer from primary yeast source to slant takes place, then, if the transfer tube is sterile and the receiving slant is sterile and the cotton bud is sterile, then all slants could be inoculated without having to re-steam the cotton bud after every transfer.

Any thoughts please.

Cheers, Hoges.

Thats right hoges you dont need to re steam the bud after the transfer keep innoculating

Franko

 

[Zwickel]

Thats right hoges you dont need to re steam the bud after the transfer keep innoculating

Franko

yeah, thats right.

Im using only one cotton tip for inocculating all slants.
When I have steamed one, I dont wait for cooling down, dip it straight into the yeast cake, there is so much yeast and the cotton tip will chill immediately, no worries.

:icon_cheers:

 

[hoohaaman]

1) Why are all you people wasting a whole slant each time you brew? Just use a sterilized (flame or alcohol) loop or needle or whatever to pull out a blob of yeast from the slant and step up a starter going: 20 mL ... 200 mL .... 2000 mL (or less). And your slant will be good to use again tomorrow, next week or next year (conditional to the answer in part 2). The photos with rows and rows of slants seems unnecessary unless the user is about to culture up a dozen or so different strains. You should never need more than three slants of any variety, and even then two of them are reserves.

I have previously used the whole slant.After sterilizing with flame,I have no space in my slants to cool on agar.Could I cool in a Iophodor solution?Or would sterilizing with metho be a better/easier solution?

Cheers

 

[Sprungmonkey]

I have previously used the whole slant.After sterilizing with flame,I have no space in my slants to cool on agar.Could I cool in a Iophodor solution?Or would sterilizing with metho be a better/easier solution?

Cheers

Just cool in the air - within 30cm of the flame. Should only take a few seconds. I actually dip in metho and lit off the flame wait 3 secs and innoculate from tube to slant. Therefore all surfaces of the loop are sterile.

 

[hoohaaman]

Sprungmonkey,I don't mean for inoculating a blank slant.Rather using a sample from an established slant to prime a starter,instead of using the whole slant as a starter.

As Steve Lacey said,take some yeast from the slant to start,the starter

Cheers

 

[Zwickel]

each time you open a slant, youll get some germs from the air into the vessel.
Its easier and anyway safer, to use a slant only once.
Also it is much easier just to put some milliliter wort into the slant and leave it closed until one can notice some yeast activities, than to fiddle some yeast cells out of the agar and transfer into another vessel.

just my 2 cent.


Cheers :icon_cheers:

 

[hoohaaman]

Thanks Zwickel,so better to make the number of slants you will use in a given period.Then to re-use a single slant more then once without Lab equipment?

I have enough space now,after changing to slants,but thought I may get away with using even less.

Cheers

 

[Zwickel]

Thanks Zwickel,so better to make the number of slants you will use in a given period.Then to re-use a single slant more then once without Lab equipment?

yeah, thats the way Im doing it. The many slants Im always producing is not only to get used by myself, its also intended to get swapped with other brewing mates around here.
So Im well known around here, always to have some yeast in stock, its my hobby in the hobby :icon_chickcheers:

 

[hoohaaman]

Haha cool,I also consider it a hobby inside the hobby

 

[Sprungmonkey]

hoohaaman,
You can do it any way you want really. As Zwickel you increase the chance of contaminating a slant and using in a ruining a batch. I don't use slants more than once but there is no issue doing it if you use aseptic technique.
When making a starter as Zwickel said you can add some sterile wort to the agar slant and step up from there. I either do that or i metho and flame my loop and take a nice loopful of yeast and inoculate it into 10-20ml of wort, but you can do it anyway you want as long as it is aseptic. I find loop easier to use than cotton buds but that just me.

 

[hoohaaman]

Thanks guys,I'm leaning more towards re-using a slant.But,then again the vials are small and cheap,so inoculating a dozen at a time doesn't phase me either.

I have a rather large yeast bank,changing to slants has freed up a large slice of the fridge.So I may as well be on the safe side and single use each slant.

I think I'd cry if I infected a batch due too poor yeast handling

 

[hockadays]

After you use the slant can't you just wash out the agar of the tube clean it then use it again next time you make up a batch of blank slants?

 

[Zwickel]

After you use the slant can't you just wash out the agar of the tube clean it then use it again next time you make up a batch of blank slants?

yes, of course you can, but.....
a brandnew and sterile tube cost only a few cent, depends on how many youre going to buy, so to clean and resterilize the tube is not worth the effort.

:icon_cheers: