About to use microwave oven for media preparation??

[mohammed salim]

Dear All,

Please give me a clarification in that, 

Microbiological media preparation or media melting by using microwave oven is a valid method??? It bring any changes in the characteristics of media unlike the conventional method(melting by using pressure cooker, boil by heating)

hope your suggestions and information,

Thanks and Reg,

Mohammed Salim

 

[Andres Despi]

Dear Salim,

 

Greetings!

Heating of prepared media Agar in microwave is safe and does not affect the nutrients required to cultivate microorganism. It will lose a bit of water but can be minimize thru putting of water in a separate flask along with prepared media.

Regards,

 

Andres

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[muthalif.roshan]

Hi Salim, 

Use of microwave for re-heating agar is not recommended by two major media manufactures OXOID & LAB M because of following reasons,

• Heating may be uneven across the total volume of the medium.
• Hot spots may occur in the vessel containing the medium leading to superheating and potential explosion of the container.

Source:

http://www.labm.com/faqs.asp?id=5#5

http://www.oxoid.com/UK/blue/techsupport/its.asp?itsp=faq&faq=tsfaq016&cat=culture+media%2C+supplements+and+raw+materials&lang=EN&c=

Regards 

Muthalif 

Sent from Samsung Mobile

[Andres Despi]

Hi Muthalif,

 

Please find solution to the hindrance mentioned;

 

 1.Heating may be uneven- this can be prevented if you slowly shake the flask after 2minutes heating/200ml in a flask or depending on the volume of media prepared. The indication is that the media should be shake when it starts to boil and re-heat further until totally dissolved/melted.

2. Hot spots can occur in the column of medium leading to superheating and explosion of the containers - doing the above techniques will avoid explosion as well as it gradually heat up and constant shaking could make the media evenly heated.

3. Microwave sterilisation is effective only where there is moisture. The inside tops of the containers, if not previously sterilised, may constitute a source of later contamination. As mentioned earlier, need to put water to lessen the dehydration.

Best Regards,

Andres

[mohammed salim]

Dear All, 

I appreciate you all for having your valuable comments.

Now I would like to know, is there any guidelines for media preparation or melting in different analytic methods like US FDA, ISO, that is boiling water bath is recommended or do not by microwave oven so and so...?

Best reg,

Salim

[Bobby Krishna Thulasi]

Muthalif,

That’s what I have heard.

Someone from the DCL had asked this question when the ICMSF folks visited the lab.

The committee members said that microwaving media is not a good idea. I can check why so and get back to you.

 

Bobby Krishna T M                                                                        

Principal Food Studies and Surveys Officer

Food Control Department

Dubai Municipality 

Mobile   :           + 971 554041340                                 Office:              +971 4 2064293

                                                           

 

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[adeola...@gmail.com]

Dear All,

Using of microwave oven is not a good idea for culture media, as we all know that microwave is using ray, though we believe that it sterilise the media but it will never be like autoclave.

 Regards

Marcus

Sent from my BlackBerry 10 smartphone.

From: Bobby Krishna Thulasi Sent: Monday, 16 December 2013 7:40 AM To: muthalif.roshan; mohammed salim; foodsaf...@googlegroups.com Subject: RE: {Dubai's Food Safety Clinic} About to use microwave oven for media preparation??

[Andres Despi]

Dear Marcus,

 

Please note that Microwave will not be an alernative for autoclaving because two have different function in media(agar) preparation. Either you will melt agar thru microwave or by hot bath you need to autoclave the media for sterilization.

 

Mr. Bobby, I read some article regarding the consequencies of re-heating media thru microwave long time ago. They doubted the microwave in re-heating because it may trap some radiation that could damaged or kill microorganism during incubation but   they did not able to prove this theory.

 

Well it is always best to use newly prepared media after sterilization to avoid possible cross-contamination during re-heating.

 

Best regards,

 

Andres

On Sun, Dec 15, 2013 at 3:08 PM, muthalif.roshan <muthali...@gmail.com> wrote: