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?

Answer 1

2. Standard Plate Count (SPC): The SPC is an estimate of the total number of viable aerobic bacteria present in raw milk. This test is done by plating milk on solid agar, incubating plates for 48 hours at 32 °C (90 °F), followed by counting bacteria that grow on plates. The SPC is used to monitor progress since the consistent application of proper milking system cleaning practices, proper milking practices, udder hygiene, and good mastitis prevention and control practices should allow dairy producers to produce milk with a low SPC, which is less than 5,000 colony forming units (cfu) of bacteria per milliliter

5000cfu/ml