Jump to content


Photo
- - - - -

Microwave sterilization


  • Please log in to reply
17 replies to this topic

#1 KFC

KFC

    Atom

  • Senior Members
  • 295 posts
  • LocationAt Your Local KFC

Posted 6 June 2007 - 10:42 PM

I was wondering if I could sterilize glass petri dishes and melted agar in a microwave oven and how long would I put it on for, if possible?
  • 0
Life is like a Bucket of Chicken

#2 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 6 June 2007 - 11:19 PM

Microwaving at least in normal ovens is comparatively inefficient. Cooking agar in it for instance is not much more (if at all) more efficient than normal cooking. The heating is too heterogenous. Also, for efficient sterilization you need heating above 100 C, which only work with some overpressure. You can for instance try to moisture your dishes and then cook it for around 20 minutes. Agar will dry in that time, though.
However, in all theses cases I still would only uses these to grow fast growing bacteria. It is very unlikely that they will be completely sterile.
  • 0

#3 Paralith

Paralith

    Molecule

  • Senior Members
  • 470 posts
  • LocationWashington, DC

Posted 6 June 2007 - 11:49 PM

I was wondering if I could sterilize glass petri dishes and melted agar in a microwave oven and how long would I put it on for, if possible?


Sterilization of agar and plates is usually done in an autoclave machine, which reaches much higher temperatures than microwaves, and are designed for sterilization. If you're working at a research facility it's standard to have one.
  • 0
Man can will nothing unless he has first understood that he must count on no one but himself; that he is alone ... with no other destiny than the one he forges for himself on this earth.
~Jean-Paul Sartre

#4 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 7 June 2007 - 12:12 AM

Actually an autoclave is not much hotter per se. The main trick is that it maintains overpressure allowing liquids to be heated up to 120 C. Essentially it is a steamcooker. Essentially you can use one to sterilize your media.
  • 0

#5 ecoli

ecoli

    murderator

  • Moderators
  • 8,606 posts
  • LocationNY, NY

Posted 7 June 2007 - 12:40 AM

Actually an autoclave is not much hotter per se. The main trick is that it maintains overpressure allowing liquids to be heated up to 120 C. Essentially it is a steamcooker. Essentially you can use one to sterilize your media.


The pressure also keeps the agar from solidifying until you're ready to make the plates.
  • 0
[14:02] <Sato> I
[14:02] <Sato> want
[14:02] <Sato> Schroedinger
[14:04] == Schroedingers_hat [~matt@CPE-121-222-209-157.lnse1.woo.bigpond.net.au] has joined #sfn

#6 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 7 June 2007 - 04:04 PM

Ehm, not really. It prevents agar from overboiling during the cooldown. You usually open autoclaves between 80 and 90C, temperatures at which agar is still very liquid. They solidify roughly ~40C.
  • 0

#7 KLB

KLB

    Atom

  • Senior Members
  • 299 posts
  • LocationPortland Maine

Posted 7 June 2007 - 11:57 PM

A couple months ago I saw a series of different news reports citing a study that found microwaving a wet sponge for about five minutes pretty much sterilized it. Microwaving a sponge after sending it through a dishwasher along with one's dishes is apparently a very good way to keep sponges sanitary.
  • 0

#8 KFC

KFC

    Atom

  • Senior Members
  • 295 posts
  • LocationAt Your Local KFC

Posted 12 June 2007 - 07:11 PM

If the bacteria have water in them wont it boil and kill them?
  • 0
Life is like a Bucket of Chicken

#9 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 13 June 2007 - 02:06 PM

In theory yes, however the field created within the oven is quite inhomogenous. Very small particles (as bacteria) can quite easily be missed.
  • 0

#10 KFC

KFC

    Atom

  • Senior Members
  • 295 posts
  • LocationAt Your Local KFC

Posted 13 June 2007 - 05:45 PM

That's to Bad,

I know a pressure cookers can sterilize agar, but can pressure cookers sterilize glass petri dishes. If they can would it be better to sterilize the agar and the petri in two pressure cookers instead of letting one sit wile the other is cooking, or is doesn't matter?
  • 0
Life is like a Bucket of Chicken

#11 ecoli

ecoli

    murderator

  • Moderators
  • 8,606 posts
  • LocationNY, NY

Posted 13 June 2007 - 11:57 PM

Ehm, not really. It prevents agar from overboiling during the cooldown. You usually open autoclaves between 80 and 90C, temperatures at which agar is still very liquid. They solidify roughly ~40C.

yeah... I'm not sure why I said that. perhaps I was thinking about temperature. :doh:
  • 0
[14:02] <Sato> I
[14:02] <Sato> want
[14:02] <Sato> Schroedinger
[14:04] == Schroedingers_hat [~matt@CPE-121-222-209-157.lnse1.woo.bigpond.net.au] has joined #sfn

#12 geoguy

geoguy

    Atom

  • Senior Members
  • 244 posts
  • LocationaAberta, Canada

Posted 14 June 2007 - 12:31 AM

If the bacteria have water in them wont it boil and kill them?


Not necessarily. If a fly is caught is entrapped in a microwave it might just fly out as if nothing happened after your dish is cooked. I'll let someone else explain the physics. Here's one link among many via Google:

http://answers.googl...dview?id=265489
  • 0

#13 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 14 June 2007 - 12:37 PM

I know a pressure cookers can sterilize agar, but can pressure cookers sterilize glass petri dishes. If they can would it be better to sterilize the agar and the petri in two pressure cookers instead of letting one sit wile the other is cooking, or is doesn't matter?


Well, to sterilize glass wares you got two options. Sterilize them in a steam cooker (I am not sure how much pressure a normal steam cooker can build up. It is possible that they do not sterilize completely), or you can just bake them at at least 180C for ~12 hours.
Usually agar and dishes are sterilized independently, and then you pour the agar under sterile condition into the dishes.
  • 0

#14 KFC

KFC

    Atom

  • Senior Members
  • 295 posts
  • LocationAt Your Local KFC

Posted 15 June 2007 - 06:52 AM

I did not mean sterilize agar and petri dishes in the same pot, I was wondering how long a steril petri dish can stay in open air before it is not steril anymore? Also, does anyone know a "cheap homemade" way to keep steril glass petri dishes steril? I was think jaring them or something like that.
  • 0
Life is like a Bucket of Chicken

#15 CharonY

CharonY

    Biology Expert

  • Resident Experts
  • 4,941 posts
  • Locationsomewhere in the Americas.

Posted 15 June 2007 - 12:25 PM

Well it depends how sterile the surrounding is and how the air movements are. If you want to store them you can put your petri dishes in a larger jar that can be sealed, sterilize them within the jar and then seal it after sterilization.
For short term you can sterilize the dish in an oven then let it stand in it until agar is done.
  • 0

#16 KFC

KFC

    Atom

  • Senior Members
  • 295 posts
  • LocationAt Your Local KFC

Posted 17 June 2007 - 01:41 AM

Cool thanks for the Info.
  • 0
Life is like a Bucket of Chicken

#17 Karen_H

Karen_H

    Lepton

  • Members
  • 1 posts

Posted 21 September 2007 - 08:52 AM

Is it possible to sterilize sea water in a microwave?
  • 0

#18 Mirabelle

Mirabelle

    Quark

  • Senior Members
  • 43 posts
  • LocationAn inch short and a minute late

Posted 22 September 2007 - 02:34 AM

Sterilization packets for steam/pressure sterilization are inexpensive and widely available and they work equally as well in a pressure cooker as they do an autoclave.
The indicators on the packets will give you some confidence that the sterilization was adequate. The packets (sealed prior to sterilization) should retain inner sterilization as long as the exterior of the packet is not compromised. However, I wouldn’t go longer than 6 months without repeating the sterilization before use.
  • 0

"Let me tell you the secret that has led me to my goal. My strength lies solely in my tenacity."
:eyebrow: -Louis Pasteur





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users