A buffet restaurant uses heat lamps at a temperature of50oC to keep the food warm. If the restaurant opens forservice at 4 pm and closes at 10 pm, some of the food items thatare not refilled frequently may sit for 6 hours at thistemperature.
The following experiment was conducted to determine whether thistemperature is suitable to maintain the food and prevent bacterialgrowth:
Beef cubes were inoculated with500,000 bacterial cells and incubated at 43-53oC toestablish temperature limits for bacterial growth. Table 1 containsthe numbers of bacteria after incubation for 6 hours, and platingon nutrient agar given in the numbers of colonies for a particulardilution.
Calculate the cfu/ml for each organismat each temperature using the formula
cfu/ml = # colonies x dilution factorx plating factor (10)
(this is what i mostly need help with,how does one calculate the plating factor? or am i just suppose tothink 10 is the plating factor and multiple the previous numbers by10?)
and draw a line or bar graph toindicate the amount of growth after 6 hours for eachtemperature.
What holding temperature would you recommend to maintain thefood with minimal contamination? Is 50oC sufficient?Assuming that cooking kills bacteria in food, how could thesebacteria contaminate the cooked foods? What disease does eachorganism
Organism | Temp.(oC) | # Colonies | Dilution |
|---|
Staphylococcus aureus | 43 | 15 | 1:1000000 |
51 | 8 | 1:10000 |
53 | 6 | 1:100 |
Salmonella typhimurium | 43 | 32 | 1:100000 |
51 | 9 | 1:10000 |
53 | 2 | 1:1000 |
Clostridium perfringens | 43 | 17 | 1:100000 |
51 | 12 | 1:1000 |
53 | 4 | 1:100 |
