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dice68
Stranger
Registered: 11/28/99
Posts: 14
Loc: Jewtah
Last seen: 22 years, 8 months
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Agar Question...
#449148 - 11/06/01 04:13 PM (23 years, 1 month ago) |
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Im using Agar Agar and nutrishonal how ever you spell it Yeast.. Im a little short on a pressure cooker at the moment what im meaning to ask is will boiling for 1 hour do anything also will it destory the nutrishinal propertys of the Agar medium? Thanks for any replys..
-------------------- Roll the dice and you may find luck and grand things or you might find hell in a box......
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kingkc
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Registered: 04/24/00
Posts: 1,064
Last seen: 6 years, 7 months
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Re: Agar Question... [Re: dice68]
#449153 - 11/06/01 04:17 PM (23 years, 1 month ago) |
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You will not have any success if you are minus a pressure cooker. In order for things to be sterile they need to get upto at least 260 degrees.
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dice68
Stranger
Registered: 11/28/99
Posts: 14
Loc: Jewtah
Last seen: 22 years, 8 months
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Re: Agar Question... [Re: kingkc]
#449170 - 11/06/01 04:27 PM (23 years, 1 month ago) |
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260 degrees you say that makes me want to ask this question would pasturization work if i set the oven to 350 degrees and let the agar in there for 2 hours would that work because the person that has my pressure cooker i am quarling with at the moment....
-------------------- Roll the dice and you may find luck and grand things or you might find hell in a box......
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pj541
member
Registered: 02/03/01
Posts: 128
Loc: fuck off
Last seen: 22 years, 7 months
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Re: Agar Question... [Re: dice68]
#449342 - 11/06/01 06:38 PM (23 years, 1 month ago) |
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i don't think that would work all the water would evaporate and i believe at that temp all the sugars (food) would carmalize.
Somebody check me.
pj
-------------------- ?Well, this is how the world works. All energies flow according to the whims of the great magnet. What a fool I was to defy him.?
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Elektrolurch
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Registered: 05/01/00
Posts: 307
Loc: Germany
Last seen: 18 years, 8 months
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Re: Agar Question... [Re: dice68]
#449852 - 11/07/01 02:00 AM (23 years, 1 month ago) |
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Hi,
autoclave agar-agar for 1 hour is no problem, when the temperature isn't to high, i.e. 121 C (250 F). Using an oven is a dry sterilization, used only for instruments or things that shouldn't get wet. A dry sterilization needs much longer and much higher temperatures, e.g. 4 h at 150 C (302 F) or 2 h at 180 C (356 F). Besides it isn't suited for sterilization of media like agar-agar, because the high temperature caramelizes the sugars, and the medium would dry out.
Pasteurization is NOT suited, becuase you will select thermoresistan spores, like the ones of Bacillus. Actually that is how Bacillus bacteria are gained/selected, including Anthrax (Bacillus anthracis) :(
There is still a method, but it is very time consuming. It bases on the fact that only the spores are thermoresitant. You have to pasteurize at the highest temp possible (95 C; 200 F or so for an hour) . Incubate at room temp for 24 h so remaining spores germinate, pasteurize and incubate again. You do this about three or four times. This method is called fractional sterilization.
Get a pressure cooker, and make your live a lot easier ;)
Elektrolurch
-------------------- "For all the time spent in that room
The doll's house, darkness, old perfume
And fairy stories held me high on
Clouds of sunlight floating by.", Pink Floyd '67
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NDK
member
Registered: 07/13/01
Posts: 186
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If you don't need the agar for germination of spores you can make peroxidated agar by just boiling as long as you don't include ingredients that break down peroxide. Generally speaking most substances that have been alive will break it down unless they have previously been heat treated. So yeast powder will but malt powder won't (it is spray dried at high temps). Dried milk will work too.
The most basic would be to make up simple malt extract agar:
20g light malt extract powder
20g agar
1 litre of water
You warm it all up in a saucepan until the agar is dissolved, then steam/boil like PF jars in a covered jar for 45 minutes. Leave to cool until it is only just warm (50C or lower) and inject c.10cc of 3% peroxide solution. Then pour as normal.
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iudexk
member
Registered: 08/18/01
Posts: 107
Loc: UK
Last seen: 22 years, 11 months
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Re: Agar Question... [Re: NDK]
#450279 - 11/07/01 01:21 PM (23 years, 1 month ago) |
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SWIM doesn't have an autoclave either, but has success by microwave at high power for 8mins.
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