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Laboratory autoclave created brown precipitate in DME agar media

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AntDoctor

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I wanted to start slanting yeast, and I work in a lab, so I have access to a real industry level autoclave. I just made my first batch of slants tonight, using 90ml water, 9g of DME, 1.8g agar. (2% agar, 10% DME)

I boiled and dissolved the agar with the DME, poured it into some upright culture tubes, loosely topped them with the tubes' caps, the put the bad boys in the autoclave for a "liquid 30" cycle.

But when I removed them from the machine and hour later, the clearish liquid had precipitated material in it. Think the appearance of flocculating yeast, although there definitely isn't any.

What's up with this? How did it happen and how do I avoid it in the future? Did the DME somehow... undissolve and caramelize?? Very confused...
IMG_20201106_204301811_BURST000_COVER.jpg
 

brewdude88

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Not 100% but that looks like break material.

Typically, when I make agar I produce 300ml of 1.040 wort, boil it, cool it and pour it off the protein break material before re-heating and mixing with agar and adding to slants and plates.
 

Vale71

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HIgher temperatures in the autoclave will cause even more hot break material to separate than with a normal boil. This is perfectly normal.
 
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AntDoctor

AntDoctor

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"Hot break," huh? Well today I learned something, so thank you! You're absolutely right, of course.
I wonder how commercial malt agar media is so clear, though I imagine they could filter it or something...
 

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