4 °C - the National Sea Grant Library

diving bell and lowered into the water for irradiation from a 60Co
source which emitted 0.017 kGy per minute. The rest of the samples
were labeled “control” and kept in the cooler. For a comparable length
of time for the irradiation, one hour of exposure would equal 1 kGy.
The diving bell was pulled up when desired exposure time and dose
were reached. Four samples were removed from the diving bell,
labeled and then placed in the cooler with ice. The diving bell was
again lowered into the source for further exposure until all the samples
were removed. The irradiated crabmeat samples were then transferred
back to the Department of Food Science where the microbiological
analyses were performed immediately. The unused samples were kept
on ice and stored in the walk-in refrigerator in the Department of Food
Science. The temperature of the ice stored crabmeat was 2°C. Every
microbiological analysis procedure was repeated three times in order
to calculate the average.
Preparation for Microbiological Evaluation
Aseptically weigh 10 g of crabmeat into a sterile plastic bag.
Add 90 ml of sterile 0.1 % peptone dilution fluid with 8.5 % of NaCI,
blend for 90 seconds with a stomacher (Lab-Blender 400, Tekmar
Co., Cincinnati, OH). This represents the 10 -1 dilution. Make further
sequential dilutions using peptone dilution fluid.
Procedures
Standard Plate Count
1. Pipet 0.1 mL from the sequence of dilutions onto pregelled Plate
Count Agar (Difco Laboratories, Detroit, MI) using the spread plate
method.
2. When the surface of the plate count agar becomes dry, invert the
plates and incubate at 35° C for 48 hours.
3. Count all plates which contained 25 to 250 colonies and calculate
the total plate count per gram crabmeat.
4. Repeat the same procedures after 7 and 14 days, respectively.