Hi, I am using FDA BAM Chapter 18 method for Enumeration of Yeast and Mould Count.
I plate 0.1ml of sample onto 3 agar plates.
Would like to ask on the results calculation. What if there is only 1 or 2 colonies grow from all these 3 plates? 2 divide 3 = 0.66
What number to take as the result?
Report as ND <100?
I assume sample is from 10(-1) dilution.
(it might have been advisable to also evaluate the 10(-2) dilution)
Note that BAM (Pour Plate method) suggests to use plates with 10 -150 colonies
By analogy to BAM's APC counting section I suggest a result <1000cfu/gram
APHA (2001) would suggest (assuming total 2 colonies) a result of 67cfu/gram (est.)
IIRC ISO have a third calculation method.
All very hypothetical.
A pour plate method using 1 ml inoculum might be helpful..