- Thu Sep 02, 2010 11:27 pm
#69359
All ingredients should be in the media before You boil it; sugar, Agar, MS, Vitamins, PGR'S (if You want) etc.
Agar type gelling agent isn't water soluable at all until boiled and requires cooking before dispensing to obtain uniformity of hardness or strength of Gelling properties from vessel to vessel. That is why People cook the prepared media. So technically You are cooking Your prepared media twice; once to dissolve the agar, and again in a pressure cooker, microwave, etc. for sterilization of the prepared media and the vessels holding it. This method gives You flexibility in how much media You want to dispense from vessel to vessel, knowing it will set up uniformly, irregardless of the amount. Agar gels upon cooling undisturbed.
You can get around the above problem of cooking twice by using a level 'smidgeon' measuring scoop per 25ml of media and dispense that little measure right into each of the vessels, swirl a bit and go into the autoclave which sterilizes and boils and dissolves the Agar all in one. You have to make sure You dispense the right amount of agar for the quantity of media in the vessel or You will end up too hard or soft on the media gel.
Carageenan type gelling agent, (I.E. GP-812) is quite popular as it is partially water soluable, dispersing uniformly so You can dispense into the vessels cold and only have to cook once (sterilization process) to activate it's gelling properties upon cooling.
With Carageenan type Gels, it's a good idea to occasionally stir the uncooked media while dispensing in the vessels, as the Carageenan can start to settle a bit making the first jars set up a little soft, and the last jars set up a little too hard.
No matter what Gelling agent You use, a little variance in hardness in media from vessel to vessel can be expected and is acceptable.
Hope this helps,
Gary
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