Australia's Science Forum

Hi all.
Does anyone out there in lab land have a surefire way to get the stock/broth Pasteur Experiment to react more quickly than the usual 2/3 weeks it takes? Teachers time is becoming less and less for experiments.
Doing it at this time of year in the coldest weather naturally takes longer. Also what stock do you all use with success?
I have been preparing this prac.for many years and sometimes it is successful and at other times it is not. Very frustrating.!!!!
Cheers
Mother xx

Put it in the incubator?

Or a sunny spot?

We used chefs cupboard stock, and little lamps to help keep it warm.

CHEAT!
Put mould deliberately into the open ones and let it grow -

We use a bit of bread and put it in a warm place works every time

Send your broth on a holiday to Cairns?

Ha did you take it, had a day at the beach?

hello,
I use the broth recipe in the laboratory book page 198 and it has always been successful after a few days for me.
10g beef extract
10g peptone
5g sodium chloride
1 litre distilled water
0.1M sodium hydroxide and 0.1M hydrochloric acid
dissolve ingredients in water by heating, adjust pH to 8-8.4, boil for 10 minutes, (filter). Adjust pH to 7.2 with hydrochloric acid.
The students then boil it again and do what they do in class, some teachers don't care if it is filtered or not. I agree it is always a cold time of the year so it may take longer but it has always worked for me.
shaz

I agree take it on holidays to some place warm I will have to come with yoou to help carry them

Cairns sounds good to me, but Noona I think I should come too to help you?

Yes Sue you need to help aswell it will take two of use to carry it and we need two weeks aswell

Sorry Mother but it is Friday.
Sue & I will help just the same if you take them to a warm place

Come on then! 27 degrees here, as I type this.

Mind you no-one is going to the beach just yet. Too many stingers still, with all this rain.

As a teacher in training, I actually just did this experiment a few weeks ago. I got the students to dissolve 1 cube of continental beef stock in 150mL of water and left them in the prep room for 1 week. They grew wonderfully! I think the trick is to use lots of stock and not to over boil them (despite the theory). I had 4 groups set it up, all open flasks grew something while none of the swan necks did. Also, why is it an issue if the experiment takes time? That is the reality of science, move on with the syllabus and come back to it?

I'm sure Pasteur didn't have results in a week. I actually thought that the stock cubes had too much salt in them for a good growth. We use stock made from chicken wings and they have worked well the last few years!

We found that the broth you buy from supermarkets never grows mould. It might in your home fridge but it never did at work. I think there are preservative sin it to prevent mould.
Boil up some chicken wings/breast whatever, strain the solids off .. it works.. warming the flasks over time works.
We put the whole prac in a tray on top of a cupboard and go back a month later... well I go back a little earlier to make sure it is growing, and if not - cheat.

THANKS FOR YOUR INPUT EVERYONE !!!!!!

So now I'm going to Cairns,much warmer than here at the moment.
Cheers
Mother

The dreaded Pasteur experiment! Do others filter your broth? My teacher likes it to be clear but it takes absolutely forever! This year I am trying Continental Stock Broth in little pottles. It says there are no preservatives but I have just read that it has thickeners and I suspect that is contributing to the globbing up of the filter paper. I put it through a sieve first but it is still taking forever.
Kathryn :(

We buy in Nutrient Broth powder. It makes a lovely clear broth.