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Food Micro Lecture 3
Food Micro Midterm 1
| T or F: Viruses grow abundantly in foods. | False |
| Yeasts require ______ compounds for growth. | organic |
| T or F: Yeasts can grow in anaerobic conditions. | False |
| What is the optimal pH for yeast growth? | neutral or slightly acidic |
| How do yeasts multiply? | Budding/spores by sexual mating |
| What food products are yeast useful for? | Alcoholic beverages, baking |
| Molds require at least _____ moisture for growth. | 70% |
| Describe the mold growth life cycle. | Extension of hypha into mycelium, spore formation, spores disperse into air, spores germinate |
| Bacteria reproduce by ______. | binary fission |
| What factors affect bacterial reproduction? | cell type, nutrients available, space, temperature, presence of toxic compounds, age of cell |
| T or F: Bacteria grow faster than yeasts and molds under optimum conditions. | True |
| What nutrients are necessary for microorganisms to grow? | water, source of energy, source of nitrogen, vitamins, minerals |
| Space limitations usually correlate with _______. | nutrient availability |
| The optimum growth temperature for most foodborne bacteria is ____. | 37C |
| T or F: Bacteria can kill themselves by producing large amounts of toxic compounds. | True |
| T or F: Old cells have a higher surface to volume ratio and thus exhibit slower growth than young cells. | False |
| What are the four microbial growth phases? | Lag, log, stationary, death |
| Describe the lag phase. | The first growth phase, the organism is adapting to new surroundings and cell numbers do not increase; they assimilate nutrients and increase in size. |
| Describe the log or exponential phase. | Cells start to increase in numbers, growth is stable and constant; first order kinetics. |
| Describe the stationary phase. | Essential nutrients become depleted or waste products build up so that growth stops; secondary metabolites are produced; population is stable. |
| Endospore forming bacteria produce endospores during the ______ phase. | stationary |
| Describe the death phase. | Viable cell count decreases; cell lysis occurs. |
| Define generation time. | The time period which is takes for bacteria to double. |
| The bacterial growth curve is ______. | logarithmic |
| Define growth rate. | The increase in cell mass per unit time during the exponential growth phase. |
| The typical growth rate for yeasts and molds is ____. | 0.2 |
| The typical growth rate for fast-growing bacteria is ____. | 2.5 |
| ____ and ____ are the most important factors which affect growth rate. | Temperature, time |
| What are three ways to quantify bacteria? | Direct measurement (microscopic count), viable cell count (plate count or colony count), indirect measurement (turbidity) |
| What are the advantages and disadvantages to direct count? | Advantage: actual count, not an estimate Disadvantage: longer, cannot distinguish between living and dead cells |
| What is the disadvantage to viable cell count? | It is not actual cell count, its a measure of CFU. |
| What is the disadvantage to indirect count? | It does not give a quantifiable number. |
| Describe growth in mixed populations. | Growth characteristics will differ depending on optimum conditions of microorganism. |
| Describe sequence of growth. | Different strains will predominate in sequence during storage; growth of one microorganism creates an environment for another and then the first can no longer grow |
| Describe growth in succession. | Includes sequence of growth, but diauxic; one or two types of microorganisms can grow optimally, then create an environment which they can no longer grow in but allow for growth of another organism |
| Describe symbiotic growth. | One type of cell produces metabolic products that another needs for growth and vice versa. |
| Describe synergistic growth. | Observed during symbiotic growth of more than two organisms. |
| Describe antagonistic growth. | The growth of one bacteria inhibits the growth of another. |
Created by:
goberoi
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