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Food Micro Lecture 6
Food Micro Midterm 1
| 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 |
| Give four types of physical stress. | Temperature, UV light, irradiation, electric field |
| Give four types of chemical stress. | pH, antibiotics, detergents, oxidative stress, preservatives |
| What do microorganisms utilize as apart of their mechanism of stress adaptation? | unsaturated fatty acids, shock proteins, stress proteins/genes |
| In gram (-) cells, rpoH and rpoE are genes for ______. | heat response |
| In gram (-) cells, rpoS is a gene for _____. | general stress |
| Define D-value. | The time needed at a given temperature for destroying 90% of microbial population. |
| Define sublethal injury. | The exposure of bacterial cells to un-favorable physical and chemical environments that can cause reversible alterations in the cells. |
| 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. |
| _____ bacteria may be able to induce an acid tolerance response to protect the cell from severe acid conditions. | Salmonella |
| What are the two hazards associated with injured microorganisms in food? | Potential capability in multiplying, undetectable in selective media. |
| What are the two preventive controls associated with injured microorganisms in food? | A short repair phase before detection, storage in preservative conditions. |
| T or F: Under certain unfavorable environments, cells may not be recovered in normal media but remain viable. | True |
| Define viability. | Cells that are metabolically active and able to multiply in an appropriate environment. |
| Define metabolically active. | Cells capable of carrying out metabolic activity but may not necessarily multiply. |
| Define nonculturablilty. | Inability to multiply under any conditions. |
| 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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