1. ???????????????? (Intrinsic Factors)

1
3. ??????????????????????????????????????????????
????

• 1. ???????????????? (Intrinsic Factors)
• 2. ???????????? (Extrinsic Factors)

2

• ???????????????? (Intrinsic Factors)
• ????????
• water activity
• ????? ???????????????-????
• ???????????????????????????
• ???????????????????????????

3

• ???????????? (Extrinsic Factors)
• ??????????????????????
• ??????????????????????????????
• ?????????????????????????????????
• ???????????????????? ???????????????????????

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??????????? (Intrinsic Factors)

• ????????
• Nitrogen sources
• - ?????????????????? ???????????????????????????
  ?????????????????????????????????????????
• - ????????????????????? ?

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• Carbon sources
• - ???????????? ????????????????????????????????
  ?
• - ???????????????????? ?????? ?
• Growth factor
• - ????????????????????????????
  ??????????????????????????????? (Coenzyme)
• - ???????????????????????

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• Mineral sources
• - ???????????????????????????????????????????
  ????????????????????????????????
  ?????????????????????????????
• - ??????????????????????????????????????????????
  ???? ??????????????????????
• - Major element ?
• - Trace element ?

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• 2. Water Activity
• - ?????????????????????? 2 ???? ???
• bound water ???????????????????????????????????
  ????????????????????????????
• free water ????????????????????????????????
• ???????????????????????????? ???????? water
  activity (aw)

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• ???????? aw
• aw ?????????????????
• ????????????
• aw ????????????????
• 100
• - aw ????????????? 1
• - aw ???????? gt 0 ??? lt 1 ( 0.1-0.99)

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aw of Food
?????? ?????? ????? ???? 0.10-0.20
?????? ??????? ???????? ????? lt 0.6
??? ?????? ????????? ???? 0.6-0.85
??????????? ????????? ????????? ????????? 0.85-0.93
???????? ?????? ???????? ??????? 0.93-0.98
??????? ????? ??? ??? ????? ?? ??? 0.98-0.99
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aw of Food

• The aw of food can be reduced by removing water
  (desorption) and increased by adsorption of
  water.
• The desorption process gives relatively lower aw
  values than adsorption process does at the same
  moisture content of a food.
• - This has important implications in the
• control a m.o by reduced the aw of a
• food.

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water
Water sorption isotherm showing hysterisis. At
the same percentage of water, Aw is lower by
desorption than by adsorption. ????? Ray,
B.(2004) Fundamental Food Microbiology. CRC
Press. New York.
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?????????????????????? aw

• High moisture foods (HMF) ??????????????
  ?????????? gt 50 aw ? 0.95
• Intermediate moisture foods (IMF) ??????????
  15-50 aw ??????? 0.65-0.85
• Low moisture foods (LMF) ?????????????
• ??????? 25 aw ? 0.65

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aw ????????????????????????

• The free water in a food is necessary for
  microbial growth
• It is necessary to transport nutrient and remove
  waste material, carry out enzymatic reactions,
  synthesize cellular materials, and take part in
  other biochemical reactions,
• such as hydrolysis of a polymer to
  monomer( protein to amino acid)

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aw ????????????????????????

• ?????????????????????????? aw ???????
• ????????? gt ????? gt ??
• ????????? G - gt G
• Aw is reduced drastically, microbial cells in a
• population lose viability, generally
  rapidly
• at first and then more slowly.
• - This information is used to control
  
• spoilage and pathogenic m.o in food

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??? aw ??????????????????????????????????????????
M.O. aw
Most spoilage bacteria 0.9
Most spoilage yeast 0.88
Most spoilage molds 0.8
Halophilic bacteria 0.75
Xerophilic molds 0.61
Osmophilic yeasts 0.61
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???????? aw ???????

• ??????????????????????????????? ???? ??????
  ????????? ?????
• ?????????? ??????????????????????? (crystal)
  ????????????????? M.O ?????????????
• ?????????????????? (solute) ????? ???? ?????
  ?????? ????
• ???????????????????????????? ?????
• aw 0.65-0.75

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??????????????????

• 1. Natural Dehydration
• - ????????? ????????????????????? ????
  ??????????????? ?????? ?????
• - ??????? ?????????
• - ?????????? M.O ??????????????????????
  ?????????????????????????????????????????

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• 2. Mechanical Drying
• - ??????????????????????????????
• - ??????????????
• - ?????????
• - tunnel drying, roller drying, spray drying

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• 3. Freeze drying
• - ?????????????????????????????????
• - M.O ???????????????? 2 ??? ??? Freezing ???
  Drying
• - ????????????????????????????????????????
• - ?????????????????????????
• - ????????????? ?????????

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• 4. Smoking
• - ?????????????? ???????????????????
• - ?? aw
• - ??????????????????????????????????
• - ??????????????????????????????????????????

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??????? aw ?????????????

• ?????????????????????
• ???????????????????? ????? aw ????????????????????
  aw ?????????????????????????
• ????? M.O ??????????????? ????????????
  plasmolysis

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3. pH ???? ???????????-????

• ?????????????????????????????????? pH 7
  (6.6-7.5)
• pH lt 4 ???????????????
• ???????????????????? pH 6.0-8.0
• ????????????????????? pH 4.5-6.0
• ???????????????????????????????? pH 3.5-4.0

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??? pH ??????? lt pH ???????????????? -
????????????? - ????????
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pH of Food

• The pH of a food can vary greatly, depend on
  type.
• Foods can be grouped as
• 1. high-acid foods (pH below 4.6)
• - fruits, fruit juices, fermented foods and
• salad dressings
• 2. Low-acid foods (pH 4.6 and above)
• - vegetable, meat, fish, milk and soups

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• ?????????????????????????????????????
  ???????????? m.o ???????????????????????
• pH ????? lt ???
• ???????????????????????????????
• ??? ??????????????????????????????
• -???????????????????????? ????????? pH
• ????????????????? rigor ?? pH 5.6
• ?????????? (6.2-6.5)

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• ??????????????????????????????????????
  ???????????????????????????? rest animals
  ????????? pH ????????????????????????
• ????????????? ?????????? 1 ????????????
  ??????????????????? lactic acid pH ?? ??? 7.4
  ???? 5.6
• ???????? rigor mortis
• - ???????? pH 5.1-6.2
• - ???????? pH 5.4-6.7
• - ???????? pH 5.3-6.9

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pH and Microbial Growth

• ????? pH ????????????????? ??????
• - ??????????????????
• - ????????????????????????????
• Cell membrane ??????????????????? H
• ??? OH- ??????????? ????????????????????
  cytoplasm ??????? ?????? pH ?????????? ?????????

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pH and Microbial Growth

• pH in a food is reduced below the lower limit
  for growth of a microbial species, the cell not
  only stop growing but also lose viability.
• Weak acids that have higher dissociation constant
  (pKa), such as acetic acid (pKa 4.8) vs. lactic
  acid (pKa 3.8) cause a reduction in internal pH.

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4.Oxidation-Reduction Potential (O/R, Eh)

• Principle
• - Redox ???? Oxidation Reduction ??? ?????????
  (substance) ??????????????????????
• - ???????????????????? e ???????? oxidation
• - ???????????????????? e ???????? reduction

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oxidation

• Cu Cu e
• ????????? e ????? reducing agent
• ????????? e ????? oxidizing agent
• 2Cu O2 2CuO
• Cu ?????????? e , O2 ?????????? e

reduction
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- ????? e ????????????????????????????
????????????????????????????????????????? 2
?????????????????????? (Redox potential Eh)
?????????? mV aerobic mo. ??????? Eh
anaerobic mo. ??????? Eh -
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Redox Potential in Food

• ??? Eh ???????????????????
• 1. chemical composition ??? ??????????
  ???????????????????????????????
  ?????????????????????????????????????? e
• 2. specific processing treatment
• 3. storage condition

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• chemical composition
• - ????????????????????????????
  ????????????????????????? (-SH group) ??????
  ????? ??????????????? ??? reducing sugar
  ??????????????????? e (reducing agent) ????????
  Eh ??????????????
• - ??????????????? ??????????? ???????????????????
  ?????????? ???? H ?????????? Eh ???????????????

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• specific processing treatment
• - processing such as heating, can increase or
  decrease reducing compounds and alter the Eh.
• storage condition
• - A food stored in air will have a higher Eh
  (mV) than when it is stored under vacuum or in
  modified gas (such as CO2 or N2)

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Redox Potential and Microbial Growth

• ????????????????????????????????????? m.o.
  ????????? m.o. ??????? 3 ??? ???
• 1. aerobes (Eh 500 to 300 mV)
• 2. anaerobes (Eh 100 to -250 mV)
• 3. facultative anaerobes (Eh 300 to 100 mV)

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• m.o. ????????????????????????????? ?????????? Eh
  ???
• m.o. ???????????????????????????????? ??????????
  Eh ??
• ????????? ?.?. ???????????????????????????????????
  ????? Eh ???????
• ????????? Eh ?? ????????????? Clostridium

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• The presence or absence of oxygen and the Eh of
  food determine the growth capability of a
  particular growth to generate energy and
  metabolic by-products. This is important in
  microbial spoilage of a food.

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5. ???????????????????????????

• ??????????????????????????????????????????????????
  ?????????????
• - allicin ??????????
• - glucosinolate ??????????? ???????? ??????
• - lysozyme ????????

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• ?????????????????????????????? ?????????????????
  ???????????????????????????????? ????
• - ??????????????????????? ???? ???? ???? ??
  ????????????? (chitin) ???????????????????????????
  ?????????
• - ??????????? (lignin) ??????????????????????????
  ???????
• - ?????????????????????????????????????? aw
  ???????????????????????????????

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• pigment ???????????????????? ????????????
  ???????????????????? (antimicrobial)
  ???????????????????????????? (antioxidant
  property)
• - ?????????????
• - catechins
• - ?-carotene
• - Flavonone

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????????????????????????????????????? ??????????
????????????????? ???????????????????????????????????? ????????????????????????????????
Antocyanin pigment ????? Bacteria (enzyme)
phenol ??????????? Aspergillus paraciticus
tannin Peanut, mint Aspergillus paraciticus antiviral
Lupulone humulone hops ????????????????
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???????????? (Extrinsic Factors)

• ??????????????????????
• ??????????????????????????????
• ?????????????????????????????????
• ???????????????????? ???????????????????????

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?????????????????????????????????????? (Modified
Atmosphere ???? MA-Storage)

• ????????????????????????????????????????
  ????????????????????????????
• ?????????????????????????????????????? ???
• - ??????????????????? ??? vacuum packaging
• - ??????????????? ???? CO2 N2
  ????????????????????????????????????? (Controlled
  Atmosphere)

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• ??????????????????????? (Controlled Atmosphere
  Packaging CAP) ?????????????????????????????????
  ???????????????????????????? ?????????????????????
  ?
• ????? ?????????????? 50 100 ,
  ????????????, ???????????????????,
  ?????????????????

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CO2

• ??????? ?????????? ???????????????
• CO2 ???????????????????????????????
• ????????????????????
• ???????????? (dry ice) (-78.5 ?C) ????????????
  ?????????????????????
• ????? mixed gas ????????????????????? (MA)
  ????????????????????? (CA) ????????

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????? CO2 ?????????????

• ????????????????? ????????????????????????????
• ?????????? T ??? ?????????????? CO2 ????????? pH
  ???? ????????????????????????????/?????
  ??????????
• CO2 ?????????????????????? ????????????????
  ????????????????????????

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• ????????????????????????
• ??????? lag phase, ?????????????????
• ???????????????????????????????????????
• ???????????????????? enz. ????????????????????????
  ? enz.
• ?????????????????????-?????????????????
• ?? pH ???????

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N2

• ?????????? ??????????????????????????????????
• ????????? ?? O2 ????????????? O2 (N2 100 )
  ?????????????????? aerobic mo. ??????????
• ?? lipid oxidation

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Ozone

• ???????????? ????????????????????????????? ????
  ??????????????
• ?????????????????????????????????
  ??????????????????????? ??????
• ???????????? ??????????????????????
• ??????????????????? ???????? ????????

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• 2. ???????????????????????????
• - ??????????????? ???????????????????????????????
  ?????? ?????????
• 1. Psychophiles ????????????? T lt 7 C
• 2. Psychotrophs ????????????? T ???
  ??? ???????
• 3. Mesophiles ????????????? T 20-45 C
• 4. Thermophiles ????????????? T 55-65 C

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??????????????????????????????????????????????
Group Minimum Optimum Maximum
Thermophiles 40-45 55-75 60-90
Mesophiles 5-15 30-40 40-47
Psychophiles -5-5 12-15 15-20
Psychotrophs -5-5 25-30 30-35
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• ???????????????????????????????????????????
  ??????
• - ???? T 15-45 C ???? danger zone bact.
  ????????????????? ??????????????????????????? T
  ???
• - ???? T 7-15 C ??????? T 45-63 C bact.
  ?????????????? ??????????????????? 2-4 ???????
• - ???? T lt 7 C ??? T gt 63 C ????????????
• ??????????

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????????????????????????????????????

• ??????? ???? ???????????????????????
• - ???????????????????
• - ????????????????
• ???????????????????

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??????????????????????????????

• ??????????
• - ??????????? ?????????? ?????????????? ???????
• - ???????????????? 0-1 C
• - ????? ????????????? ???
• cross contamination

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• ?????????? (Refrigeration)
• - ??????? ??????????? ???????????????????
• - ???????? 4-5 C
• - ????????????????? (?????????? ???)
  ???????????? T lt 4.4 C ( 1 C )
• - ?????????????? ???????????????? ???????????
• ????????????

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• ????????????
• - ?????????? ?????????? ??? ???????????
• - ??????????? lt -10 C
• Home freezer -20 C
• ??????????? -78 C
• ???????????? -196 C
• - ????????????????????? -20 C ?????????????
• ??????????????????????

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?????????????????????????????

• 1. ??????????? enzyme ???? ???????? heat-stable
  proteinase ??? lipase
• - enzyme ????????
• - ?????? denature ??????? coagulate
• - ?????????????????????????????
• - DNA ????????????

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?????????????????????????????

• 2. ?????????????????????????????????
• - aw ???????????? M.O ???????? ?????????
• - ????????????????????? ??????????????? ????????
  ????????????????????? M.O ???

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• 0 to -1 C
• - Psychrophile lag phase, exponential phase,
  germination time of spore ???????
• - Mesophile ??? Thermophile ?????????????
• -2 C
• - ?????????????????????? ???????????????
• - T ??????????? aw

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????????????????????

• slow freezing
• - ??? T lt 5 C , 3 72 ???????
• - ???????????????????
• - ???? solution effect
• ????????????????????????? ???????????
  ?????????????? ???. ???????????????? (aw )
  ????????????????????? (pH )
• ?????????????? ??????????????????????????
• - ????????????

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????????????????????

• quick freezing
• - ??? T 17.8 ??? -45.6 C , ??????? 30 ????
• - ???????????????????
• - ???????????? solution effect
• - ??????????????????????????

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???????? Freeze-Thaw

• Cell wall ??? cell membrane ??????
• ??? DNA ??????
• Ribosomal RNA ????????
• Enzyme ????????????????
• Sublethal (repairable) injury
• - Structural and functional injuries are
  reversible
• Lethal injury
• - The damage are irreversible

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????????????????? (High Temperature)

• ?????????????? ??????????????? ???????????????
  ??????????
• ????????
• - Pasteurization
• - Sterilization

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Pasteurization

• ??????????? T lt 100 C
• ??????????????????????????????
• ??????????????????????????????????
• ???????????????????
• - 63 C , 30 min (low temp, long time LTLT)
• - 72 C, 15 sec (high temp, short time HTST)

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• - 82.3 C , 25 sec
• - 76.7-93.3 C , 1-3 sec
• - 74 C , 15 min
• ?????????????????????????
• - Mycobacterium tuberculosis ??? Coxiella
  burnetii
• - Yeast, mold , bact G- ??? G ????????????

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Sterilization

• ??????????? T ??????? 100 C
• ?????????????????????? ????????????
• ?????????????????????????????? ????????
  commercial sterilization
• ??????????????? commercial sterilized food
• - ????????????
• - ?? UHT (135-150 C, 1-4 sec)

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???????????????????????????????

• ?????????????????????????????????????????
  (denature) ?????????????????????????
  (coagulation) ?????????????
• ????? DNA ??????
• ????? cytoplasm

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???????????????????????????????????????????????

• ??????????????????????????????????????????????
  ??????????
• ?????? cell ??? spore ????????
• ??????????????????
• ?????????????????

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• D-value
• ???????????? ????????????????????? ???????????
  ????????????????????????? 90 ???? 1 log
  cycle
• Z-value
• ?????????????????????????????????????????????????
  ? D ?? 1 log cycle
• F-value
• ????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ??????????

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4. ???????????????????? ???????????????????????

• m.o ?????????????????????????????????????????????
  ? m.o ??????? ???? ??? m.o ???????
• ?????????????????? antibiotic, bacteriocin,
  H2O2, ????????????????
• lactic acid bacteria ?????????????????????
  ?????????
• - ?????????????????
• - ??????????????????????????
• - bacteriocin