Intrinsic Parameters Flashcards
intrinsic parameters
aw pH Redox potential Nutrient content Vitamins Antimicrobial constituents biological structures competitive microflora
Water activity (aw)
- Moisture content
- Ratio of water vapor pressure of pure water at the same temperature
aw formula
P/Po
P = vapor pressure of solution
Po = vapor pressure of solvent
Relative Humidity
100 x aw
Common aw values
Pure water: 1.00
22% NaCl: 0.86
Fresh food: >0.99
Min aw value for microbial growth: bacteria
0.90
Min aw value for microbial growth: yeast
0.88
Min aw value for microbial growth: mold
0.80
Low aw:
Increases lag phase
Decreases growth rate
Decreases max population
aw lowering food additives
NaCl
KCl
Carbs
Phosphates
growth decreases as…
aw decreases
Best microbial growth pH level:
6.0 - 7.5
Few organisms grow at pH below
4.0
No growth of C. botulinum at or below
4.6
Butter pH
6.1 - 6.4
Milk
6.3 - 6.5
Fish
6.6 - 6.8
Beef
5.1 - 6.2
Chicken
6.2 - 6.4
Buffering capacity: meat
High
Buffering capacity: produce
low
Oxidation
Loss of an electron
Addition of O2
Reduction
Gain of electrons
Removal of O2
Reducing agent
Substance that gives up electrons or acquires O2
