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FoodMicroLecture 21

Final Exam

Describe the hurdle concept. One preservative isn't enough for all microbial safety and stability.
T or F: Growth, survival, and inactivation of microorganisms in foods are not reproducable responses. False
A _____ model can quantitatively describe the combined effect of environmental parameters. mathematical
What are two types of tests used in predictive microbiology? Challenge testing, storage trials.
Define a primary model. Describe changes in microbial numbers with type (eg. D-value).
Define a secondary model. Describe how parameters in a primary model change with different environmental parameters (eg. Z-value).
Define a tertiary model. Describe secondary models with user-friendly interface for non-modelers.
What is the flow from data generation to modeling? Data generation, primary modeling, secondary modeling, product validation, tertiary modeling.
Define thermal death time. The time necessary to kill a given number of microorganisms at a specified temperature.
T or F: Thermal death is first order process. True
Microbial death rate due to heat can be expressed as a function of____ and ____ under a given condition. time, temperature
T or F: Rate of cell death is directly dependent on the number of viable cells present at a given lethal temperature. True
Define decimal reduction time (D-value). Time at a given temperature for a microbial population to be reduced by 1-log.
Define Z-value. Temperature change which results in a 1-log change in D-value; calculated from log-D versus temperature.
How would the thermal death curve appear if the population contained a mix of species? Tailing would be observed.
Created by: goberoi