Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
18 Cards in this Set
- Front
- Back
|
What do extrinsic factors refer to? |
environmental conditions that affect microbial growth on food |
|
|
What does temperature do to a microbe? |
- has a major effect on microbial growth, physiology, and gene expression |
|
|
At what temps. can microbes grow? |
- at a range of -8 to 100 degrees celcius |
|
|
What are the five types of microbes with respect to temperature?
|
-psychrophiles -psychrotrophs -mesophiles -thermophiles -extreme thermophiles |
|
|
What are the effects of decreasing temperature? |
Increases proportion of unsaturated and/or shorter chain fatty acids in cell membranes |
|
|
What are the effects of increasing temperature? |
-Denaturation of proteins -Thermal breakdown of cell membrane |
|
|
Regarding gaseous atmosphere, how does Carbon Dioxide work? |
-lowers pH due to its dissolution in water to carbonic acid -able to penetrate the cell membrane to lower intracellular pH -may change physical properties of cell membrane key enzymes -reacts with protein amino groups changing their properties and activity |
|
|
What are implicit factors? |
Properties of the organisms themselves; how they interact with everything |
|
|
How is the physiological state of the organism an implicit factor? |
- cells growing exponentially are more sensitive to stresses than those in stationary phase - pre-adaption to stress will enhance survival |
|
|
What is mutualism? |
The growth of one organism stimulates the growth of another |
|
|
What is antagonism? |
The growth of one organism inhibits that of another |
|
|
What does lactic acid bacteria do? |
- produce lactic and acetic acids which lower pH and in turn inhibit microbial growth - produces bacteriocins which also inhibit |
|
|
What is the hurdle concept? |
Application of combined preservative factors to reduce microbial growth and survival and enhance food stability and safety |
|
|
What are the three theories on how the hurdle concept operates? |
-homeostasis disruption -metabolic exhaustions -stress reactions |
|
|
Explain the homeostasis hurdle concept? |
-disruption of microbial homeostasis temporarily or permanently by hurdle factors will increase the lag phase and inhibit growth |
|
|
Explain the metabolic exhaustion hurdle concept? |
-application of sub-lethal hurdle strains microbial repair mechanisms, uses available energy and may lead to cell death |
|
|
Explain the stress reactions hurdle concept? |
-synthesis of stress shock proteins may be induced which could enhance survival, but may be less effective under multiple stresses applied at once |
|
|
How could one predict food microbiology? |
-challenge trial -mathematical models |
