| Temperature | - strong impact on microbial growth
- microbial growth rate reduced at low temperatures
- for every 10 C rise in temp, rate of microbial growth doubles
- determines the microbial group that will dominate (ex. psychrotrophs, mesophiles)
- many molds can grow at refrigerator temperature
- consider quality of some foods |
| Temperature Danger Zone | 40-140F or 4.4-60C
most rapid growth at 90F/32C |
| Relative humidity (RH) | amt of moisture in atmosphere
- affects the water activity of stored foods
- packaging is important for food quality
- low RH can dehydrate moist foods
- high RH can increase aw of dried food products
- high RH --> condensation on food surfaces, causes microbial growth |
| Gaseous atmosphere | - type and concentration of gases in the food environment
- can affect the oxidation/reduction potential (Eh) of foods
- influences microbial type(s) that will dominate the stored food product
- vacuum packaging and modified atmosphere packaging are used |
| Presence of competing microbes | can produce inhibitory substances (antibiotics, bacteriocins, hydrogen peroxide, organic acids) |
| Hurdle technology concept | a multiple factor systems approach to control foodborne microorgansims, "barrier concept"
- manipulate two or more factors to control microorgansims
- can improve shelf-life and safety
- hurdle examples: salt/nitrite/phosphates, herbs and spices, heating/smoking, vacuum-packaging, refrigeration temperature |
