Investigating the effect of ‘probiotic’ yoghurt drinks on intestinal health - page 3
Keywords: probiotic stomach conditions bacteria dillution and plating series experiment bifidobacteria
By xbryonyx on 13/02/2007
Level: A Level (Year 12) / AS Level
Page Number: 3 of 3 pages: 1 2 3
can be multiplied by the dilution factor to obtain the titer of the bacteria sample. Since dead bacteria will not form bacterial colonies I will then be able to work out just how well the ‘friendly’ bacteria survive.
I will conduct four replicates in order to obtain an average value for the survival of the bacteria giving as accurate results as possible.
All equipment used in the experiment will be sterilised to avoid contamination which would result in inaccurate results.
Variables
The dependant variable in this experiment will be the number of bacteria that survive the replicated stomach conditions. The independent variable will be the number of bacteria placed in the stomach in order to find the amount needed in order for an influential amount to survive, if this is possible. The controlled variables in my experiment will be the PH (2-3), temperature (37 degrees Celsius) and the volume of acid placed in the ‘stomach’ (700 mls) as this will replicate the natural conditions as best as possible on a simple level. I will ensure these variables remain constant by using an accurate thermometer and PH meter and accurately measuring out the required volume of acid.
The Control Experiment
For my control experiment I will use the amount of bacteria found in a bottle of Yakult (roughly 6.4 billion) as this will show the effect the recommended dose of bacteria has and if, indeed, ‘probiotic’ yoghurt drinks make any significant difference. This will also provide a base from which we can compare how the possible addition of fewer or more bacteria as a supplement to our diet may have an effect.
Results
Number of bacteria placed in ‘stomach’ Number of bacteria survived
1 2 3 4 Average
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