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CatsLoveHouseMusic
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How long can you keep agar in fridge?
#26812340 - 07/09/20 08:28 AM (3 years, 6 months ago) |
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I’ve had like 30 agar plates in my fridge for a like 2-3 weeks. I’ve transferred agar successfully that’s been in the fridge this long before, just curious how long is too long to stay in the fridge? I bet how you made your agar plays a roll, but just curious.
Edit: what I mean by how you made you’re agar, I feel that if it’s firmer, maby it’ll dry out quicker? Not sure
Edited by CatsLoveHouseMusic (07/09/20 08:37 AM)
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Mycobro420
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Insulated lunch box keeps them for a few years.u have to worrie about temp swings if not in insulated lunchbox
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CatsLoveHouseMusic
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Re: How long can you keep agar in fridge? [Re: Mycobro420]
#26812379 - 07/09/20 08:56 AM (3 years, 6 months ago) |
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Ya someone told me that before, that’s also a variable good call. I keep mine in one of the drawers in the fridge, so it keeps the temp pretty good. A month isn’t so bad then from the sounds of it.
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Pastywhyte
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Stiffer agar does dry out faster. You can also put plates in ziplocs to give em more life, especially people in dry climates.
However I wouldn’t try and keep a colony on a plate in the fridge for more than 6 months. Longer than that and other methods like slants become preferred.
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Mycobro420
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Re: How long can you keep agar in fridge? [Re: Pastywhyte]
#26812419 - 07/09/20 09:21 AM (3 years, 6 months ago) |
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Stiffer agar? I use mea and I think that's pretty stiff. would pda be a softer recipe. I used mea to blenderless LL and the agar puck barley broke up after shook in sterlized water.put to spawn bags an still colinized fine.also pasty your one of my favorites on the sight. one of the best forsure
Edited by Mycobro420 (07/09/20 09:23 AM)
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CatsLoveHouseMusic
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Re: How long can you keep agar in fridge? [Re: Mycobro420]
#26812427 - 07/09/20 09:25 AM (3 years, 6 months ago) |
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I also use MEA, from my understanding it depends on how much actual agar you use. The more you use the stiffer it’ll become, from my understanding. What’s your recipe amounts? I use a 500ml media bottle, basic recipe was 10g agar, 10g malt I believe but I only fill mine to around 400-420ml so I use 8g agar 8g malt.
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Mycobro420
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I order pre mixed mea from outgrow. I have never made my own. so it calls for 38g of mea to 780ml of distilled water.that gives me about 20-25 dishes.
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Mycobro420
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Re: How long can you keep agar in fridge? [Re: Mycobro420]
#26812592 - 07/09/20 10:46 AM (3 years, 6 months ago) |
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Also for storage I put each one in individual bags. Then put them in insulated lunch box.have never stored longer that 3 months I'd say.try to use them fast as I can
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meowjinx
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Re: How long can you keep agar in fridge? [Re: Mycobro420]
#26812935 - 07/09/20 01:29 PM (3 years, 6 months ago) |
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You can calculate the relative "stiffness" of the agar by doing a percent (by weight is how I usually do it) calculation. The percentage would be broken down into agar, nutrients (I use potato flakes and Karo syrup), and water
Calculating the mass of water is easy because the density of water is approximately 1 g/mL. So 780 mL = 780 g
All you would need to do is read the recipe on your MEA mix and check what fraction of it is the pure agar. That would be your numerator. Your denominator would be the total mass of your agar solution, which would vary depending on how much water you use
You can't vary the ratio of agar to nutrients since your mix is pre-made, so you can only vary the amount of water, but the calculation would look like this
(Mass of agar-agar)/[Mass of agar-agar (static) + mass of nutrients (static) + mass of water]
Don't quote me on this, but I believe that the percentage of agar-agar should range between 2.0 to 2.5%, with more agar-agar being stiffer
So if you want a less stiff agar (let's say 2.0%) you would do a basic algebra calc to figure out what mass of water you would need:
(Mass of agar-agar)/[Mass of agar-agar (static) + mass of nutrients (static) + mass of water] = 0.02 (percent in decimal form)
Mass of water (for 2% agar-agar) = [(mass of agar-agar/0.02] - mass of agar-agar - mass of nutrients
And since density of water is 1 then Volume of water (for 2% agar-agar) = Mass of water
Sounds overly complicated lol, but just showing you that it's not impossible to adjust the "thickness" of your agar as long as you calculate the right volume of water and as long as the MEA that you buy specifies its mass in agar-agar and mass in nutrients
The only thing you CAN'T do is tweak the percentage of nutrients in relation to agar-agar. That part is fixed. By adding or increasing the amount of water that you add you are either diluting or increasing the concentration of those nutrients, which may push them outside of their recommended ranges. That's why I prefer making my own agar. It's super cheap and I can control exactly what goes into it and in what amounts
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Pastywhyte
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Re: How long can you keep agar in fridge? [Re: meowjinx] 1
#26812984 - 07/09/20 01:49 PM (3 years, 6 months ago) |
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Agar stiffness can range from 1% to 3% with 2% being the average.
Nutes can range from 0-4% although people have reported fine results with concentration as high as 8%. Personally if you can do brf paste then it doesn’t really matter how many nutes you use. Just be aware that more solids will increase sterilization times and lower nutes can promote certain types of growth. Higher amounts of nutes may result in slow growth.
Soft nutritious agar is better for spore germination while stiff and low nute agar is better for running culture.
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meowjinx
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Re: How long can you keep agar in fridge? [Re: Pastywhyte]
#26813007 - 07/09/20 01:57 PM (3 years, 6 months ago) |
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Yes! All of the info I posted was based on Pasty's TEKs and threads. I've followed them to the letter and my agar has always been super cheap and works perfectly. Listen to what he says!
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Bsdgaou

Registered: 02/20/19
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Re: How long can you keep agar in fridge? [Re: meowjinx]
#26814020 - 07/09/20 11:51 PM (3 years, 6 months ago) |
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With fridge you mean +3°C or -18°C?
Second question where to store slants for like 1 year? I guess this is not gonna work with petri dishes.
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w00tmycelium
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Re: How long can you keep agar in fridge? [Re: Bsdgaou]
#26814038 - 07/10/20 12:00 AM (3 years, 6 months ago) |
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I currently have some MEA plates working perfectly fine with zero contams, after sitting in the fridge for 6 months. They seem to be growing just slightly slower, but who knows what that means... could just be the strain or the plate composition in general.
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CatsLoveHouseMusic
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Re: How long can you keep agar in fridge? [Re: Bsdgaou]
#26814052 - 07/10/20 12:11 AM (3 years, 6 months ago) |
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I had to look this up as I use Fahrenheit, but our freezers are -18 so fridge is around 3 C. I haven’t done a slant as of yet sorry bud!
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