Food Micro Midterm 1
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| A situation whereby a brief exposure to a ______ physical or chemical environment that enables the cells to _____ subsequent exposure to the ______ types of harsher treatment to which it is normally susceptible. | suboptimal, resist, same
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| Give four types of physical stress. | Temperature, UV light, irradiation, electric field
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| Give four types of chemical stress. | pH, antibiotics, detergents, oxidative stress, preservatives
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| What do microorganisms utilize as apart of their mechanism of stress adaptation? | unsaturated fatty acids, shock proteins, stress proteins/genes
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| In gram (-) cells, rpoH and rpoE are genes for ______. | heat response
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| In gram (-) cells, rpoS is a gene for _____. | general stress
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| Define D-value. | The time needed at a given temperature for destroying 90% of microbial population.
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| Define sublethal injury. | The exposure of bacterial cells to un-favorable physical and chemical environments that can cause reversible alterations in the cells.
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| Name three cellular changes which can occur from cell injury. | Structural/functional changes, loss of permeability barrier, degradation of genetic materials, autolytic activity, damage to spore cortex.
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| _____ bacteria may be able to induce an acid tolerance response to protect the cell from severe acid conditions. | Salmonella
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| What are the two hazards associated with injured microorganisms in food? | Potential capability in multiplying, undetectable in selective media.
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| What are the two preventive controls associated with injured microorganisms in food? | A short repair phase before detection, storage in preservative conditions.
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| T or F: Under certain unfavorable environments, cells may not be recovered in normal media but remain viable. | True
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| Define viability. | Cells that are metabolically active and able to multiply in an appropriate environment.
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| Define metabolically active. | Cells capable of carrying out metabolic activity but may not necessarily multiply.
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| Define nonculturablilty. | Inability to multiply under any conditions.
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| Define resuscitation. | Metabolically active cells changed from a state of inability to multiply in one environment to a state of ability to multiply in another.
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