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Food Micro Lecture 4

Food Micro Midterm 1

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



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