Food Micro Midterm 1
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| Give four examples of intrinsic factors. | Water activity, moisture content, pH, redox potential, antimicrobial constituents
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| Give three examples of extrinsic factors. | Temperature, relative humidty, concentration of gases in the environment
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| T or F: Inability to utilize a component in a food gives competitive advantage for that microorganism over others. | False
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| T or F: Molds require less nutrients than bacteria to grow. | True
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| ____ are more capable in converting complex molecules into simpler forms. | Yeasts and molds
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| All microorganisms require _____ to grow and metabolize. | water
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| T or F: Bound water is available for biological functions. | False
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| Define water activity. | Free/available water in food.
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| Name three things which can lower water activity of a food. | Salt or sugar addition, freezing, drying
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| Reducing water activity prolongs the _____ phase, lengthens the generation time in _____ phase, and lowers the max number of microorganisms in _____ phase. | lag, log, stationary
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| In an environment with low water activity, which growth functions are affected in the cell? | nutrient/waste transport, enzymatic reactions
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| T or F: Gram negative bacteria require a higher water activity than gram positive species. | True
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| T or F: In food with a higher water activity, yeasts and molds will predominate. | False
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| A low acid food has a pH > _____. | 4.6
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| Most food have a pH < _____. | 7.0
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| Give an example of a food buffer. | Milk
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| Give three examples of strong acids. | Hydrochloric, sulfuric, phosphoric acid
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| Most microorganisms grow best at a pH range _____. | 6.6-7.5
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| T or F: Yeasts and molds grow at a lower pH than bacteria. | True
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| How should low-acid foods be treated? | With heat to destroy microorganisms and spores of health concern.
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| pH 4.6 is the minimum pH for _______ spores to germinate, grow, and produce toxin. | Clostridium botulinum
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| Water activity of 0.85 is the minimum for growth of ______. | Staphylococcus aureus
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| Define redox potential. | The ability of a substrate to gain or lose electrons.
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| Give two examples of foods with antimicrobial properties. | Egg whites, spices, milk
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| ____ can increase the heat resistance of C. botulinum spores. | Lysozyme
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