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level: L12B Extrinsic Factors

Questions and Answers List

level questions: L12B Extrinsic Factors

QuestionAnswer
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 Zone40-140F 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 microbescan produce inhibitory substances (antibiotics, bacteriocins, hydrogen peroxide, organic acids)
Hurdle technology concepta 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