24. Investigation into the numbers of bacteria in milk
- 00:43 Why must the fermented milk be diluted before plating?
- 01:50 Why is the Petri dish taped?
- 01:58 Why is the culture incubated at 25oC?
- 02:00 What is the assumption that is made about the number of colonies counted?
- 02:14 What is the total dilution factor by which you multiply the number of colonies counted to get the number of bacteria in 1cm3 original fermented milk?
2 samples of fermented milk e.g. Yakult or Actimel one with a distant use-by date and one at its use-by date
screw-cap bottles e.g. universal bottles
plating and growing samples
9cm petri dishes
molten MRS agar, maintained at approximately 50oC
Growing microbes – contamination with other microbes
Growth of pathogens
Molten MRS agar
Risk of scald
Handle with care