CASE STUDY: DETERMINING THE EFFECTIVENESS OF A FOOD PRESERVATIVE Background To d

Question

CASE STUDY: DETERMINING THE EFFECTIVENESS OF A FOOD PRESERVATIVE Background To determie tested for its a chemical was tested for its ability to inhibit a newly synthesized chemical might be a useful food preservative, the bacterial Control 500 ml of cottage cheese was inoculated with 2 ml of a 24-hr culture of Pseudomonas aeruginosa and incubated at 25°C. Five hours after inoculation, a standard plate count showed there were 200 bacterial cells/ml in the cottage cheese. After 29 hours at 25°C, there were 61,000,000 cells/ml in the cottage cheese. Experiment 500 ml of cottage cheese containing the preservative was inoculated with 2 ml of a 24-hr culture of P. aeruginosa. After 6 hours of incubation at 25°C, a standard plate count was performed. There were 700 bacterial cells/ml in the cottage cheese. After 18 hours, there were 1,000,000 bacterial cells/ml in the cottage cheese. Nember Log 0.00 0.30 0.70 0.78 1.38 1.51 2.30 2.85 6.00 24 32 200 700 1.00 x 10 6.10 x 10 6.10 x 10 6.79 7.79 Questions How did the control cottage cheese and the experiment cottage cheese differ? Was this experimental design valid? 1. (2 points)

Explanation / Answer

Control cottage cheese was inoculated with 2 ml of 24 hr culture of Pseudomonas aeruginosa without preservative. Whereas, the experimental cottage cheese was inoculated with 2ml of 24 hr culture of Pseudomonas aeruginosa with the addition of food preservative.
In my opinion, the experimental design is faulty, standard plate count should be taken at the same time for control and experimental group for comparison of the effectiveness of food preservative. As per the experimental data, the food preservative was able to control the growth rate of bacteria in the experimental group.

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