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15 Cards in this Set
- Front
- Back
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What are the 8 control methods to reduce microbes?"
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Low Temp, Reduced Aw, Low pH and organic acids, High temperature, Irradiation, Modified atmospheres, Antimicrobial preservatives, Nonthermal processing techniques, Physical removal
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What are factors affecting microbial growth>
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Intrinsic (ph, oxiredux) and Extrinsic (temperature, humidity, concentration of gases, other microbes competing)
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Why is freezing stressful or lethal to microbes? What are commercial technologies for low temperatures?
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Denatures and destabalizes macromolecules, water crystals damage cell components, freezing-thawing cycles may be lethal.
Commercial interests use ice chilling, refridge, and freezing |
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why is freezing and thawing impractical for commercial purposes of killing microbes?
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food quality suffers the freezing and thawing process. May take several cycles to kill bacteria, making the food undesireable to eat.
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How does a blast freezer work? How is it beneficial to food quality?
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Strong air current of Co2 of liquid N circulate through closed tubes that the food runs through. Causes rapid freezing of food and reduces size of water crystals.
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What are Aw's effects on microbial growth and what is its overall effect on cells? How does commercial dehydrate food?
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Spores depend on water to grow. No H20 = no spores, effects viability of cells.
Effect on cells is enzyme inhibition, osmotic shock and plasmolysis (water inside cells is mitigated outside, dehydrating cells). Commerical naturally dehydrate (sun), freeze dry, and mechanically dry (tunnel, roller or spray), foam dry, smoke (salmon), and concentrate or evaporate |
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What are the three different pasteurization procedures?
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LTLT - 30min@145˚C
HTST - 15sec@161˚C Egg Pasteurization - 100min@136˚C |
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What is the definition of commercial sterilization? What organisms are left after this procedure?
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food not completely sterile, but free of pathogens and mesophilic spoilage organisms. Thermophiles and spores may still be present
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What are sterilization (commercial) methods?
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Canning @ 121˚C
UHT 1-2sec@150˚C |
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What are the D, z and F values?
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D = time (min) it takes at given temp to decrease viability by a factor of one log (90%)
z=number of degrees it takes to change the D value by a factor of ten (one log or 90%) F=time required to kill a specific number of cells having a specific z value at a specific temperature |
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What is the reference organism used for the Fo value?
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Cloistridium botulinum
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What is the equation for Dt?
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DT=TIME/LOGN1-LOGN2
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What is the equation for z?
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z=T2-T1/LOGN1-LOGN2
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What is the TDT, or thermal death time?
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Time necessary to kill a given # of microorganisms at a specific temperature
Limited practical use |
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What is the requirement for canning>?
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12D reduction in cells
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