Extrinsic Parameters Flashcards
Extrinsic Parameters
Time & temp Relative humidity Atmosphere Added microorganisms Added chem preservatives
Hurdle Concept
Use multiple intrinsic/extrinsic parameters to limit microbial growth
temp, MAP, NaCl, pH, chemical preservatives
Types of microorganisms
Psychrophylic
Psychrotrophs
Mesophilic
Thermophilic
Mesophil doesn’t grow at what temp?
Temps below 10C
Psychrotroph grows at
refrigeration temps
What is the most important factor in determining shelf-life and minimizing growth of pathogens?
Storage temperature
Major cause of food borne illness
Temperature abuse
Low aw + high RH
Water gain
High aw + low RH
water loss
Controlled atmosphere
100% CO2, extends shelf-life of meat, fish, fresh produce, inhibition greater at lower temps, shift from gram- to gram+ (lactic)
2 ways to inhibit microorganisms using gas
- modify gas comp (O2, CO2, N2) within pkg to inhibit growth (vacuum pkg)
- use of gas (such as ozone - O3) and chlorine dioxide (ClO2) to inactivate microorganisms by oxidation
Lactic acid bacteria
Production of acid w/ decrease in pH
NaCl
- drying effect on microorganisms
- lowers aw
Nitrates/nitrites
- stabilize red meat color
- inhibit spoilage organisms
- inhibit pathogens
- C. botulinum: inhibit vegetative growth, prevent spore germination
Acidifying agents
- Inhibition not based on pH alone
- Inhibitory activity: dissociation constant (pKa)
- Undissociated form of acid most inhibitory
