1. Design a dilution scheme for a raw milk sample. You transfer 10 microliters o

Question

1. Design a dilution scheme for a raw milk sample. You transfer 10 microliters of the original sample into a tube containing 990 microliters. You plate 100 microliters and count X amount of Colonies. Depict this dilution scheme, making sure to include dilution factors, dilute the volumes etc. be sure to include DF of your tube and the OCD of the sample. Make sure your design allows for countable plates.

2. If you wanted to drink the milk from the sample in the previous question, would it be safe? What amount of CFU/ ml is deemed safe?

Explanation / Answer

10?l milk in 990?l water -1:1000 dilution, Dilution factor or DF= 1000

now, if 100 ?l from this diluted milk sample is used to plate and gives X number of colonie, then we can calculate cfu/ml from this calculation

cfu/ml = colony number x dilution factor X volume used for culture plate

           = x X 1000 X100 =   x X 105

2. for raw milk total bacteria count should be below or around 30,000/ml or 3 X 105

thus the milk which has produced before is probably not safe as it will contains more microbes than noted,

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