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Post by flytrapcare.com on Nov 5, 2008 19:57:45 GMT -5
Do you guys use pressure cookers to sterilize your jars and media? If so, do you have to have one of the fancy ones with a pressure gauge on it, or can you just use a regular stove top pressure cooker?
I'm slightly confused because I've read that your supposed to keep the pressure at 15psi and the temp at 121C (250F) for 15 to 20 minutes. However, most pressure cookers I've seen don't have a gauge or a thermometer. So how can you tell what the temp and pressure is?
The only ones I've seen with a gauge are the pressure canners and they only have a pressure gauge, not a temp gauge.
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Post by carnivoure12 on Nov 5, 2008 20:17:18 GMT -5
You can use a regular cooktop pressure cooker, they usually maintain that amount of pressure, atleat all the ones i used to own did, the ones with gauges are just fanshy smashy pots which are more for proffesional cookers who need to customize the pressure.
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Post by lloyd on Nov 5, 2008 20:30:05 GMT -5
I checked mine with the manufacturer-Presto. They said that it was a 15 psi pressure cooker. I think it was US$50 with free shipping in the USA. It works fine. It has a little weight that maintains 15 psi. I've used it for TC and it works perfectly, good for cooking too.
However since you live in Boulder you will likely need a fancy one with higher PSI. The higher the altitude the lower the temperature at a given pressure. Check the manufacturer and the web. It must be able to sterilize at your ambient air pressure.
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Post by flytrapcare.com on Nov 5, 2008 20:43:31 GMT -5
I did some more reading and found out that most pressure cookers do have the standard 15 PSI. Thanks for the quick feedback everyone. Because Lloyd took it a step further and threw altitude into the equation (thanks for pointing that out -- I hadn't really thought about it), I decided to look for more information with regards to using a pressure cooker at altitude. Here's what I found: missvickie.com/library/altitude.htmlThe important part there from what I can understand is this: For every 1000 ft above 2000 ft elevation, increase the cooking time by 5%. So Boulder is at about 5200ft. That means I am 3200 ft above 2000 ft of elevation. I'm guessing that would be a 16% (3.2 * 5%) increase in cooking time for me. Does that make sense? So instead of 20 minutes, I'd run for 28 minutes?
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Post by flytrapcare.com on Nov 5, 2008 20:44:54 GMT -5
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Post by lloyd on Nov 5, 2008 23:06:51 GMT -5
www.ext.vt.edu/pubs/foods/348-078/348-078.html The most resistant organisms (except for extremeophiles which we don't have to deal with) are anaerobic spores such as Clostridia which can survive up to 240F. I looked it up and for 4000-6000' 13 psi is Ok so a 15 psi model should be Ok for Boulder. Order a Presto model from Amazon, made in USA, high quality, easy parts availability, free USA shipping.
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Post by flytrapcare.com on Nov 5, 2008 23:48:36 GMT -5
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Post by lloyd on Nov 6, 2008 13:18:11 GMT -5
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Post by panduka2007 on Dec 18, 2008 19:29:51 GMT -5
hi all. I am intend to do plant tissue culture as a hoby i am in mississauga ontario. please let me know where can i find chemicals such as micro nutrients and macro nutrients (all chemicals used in tissue culture)hormones vitamins and agar or phytagel. thanks mahen
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