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FOOD MICROFLORA (SOURCES OF MICROORGANISM IN FOOD (SOIL AND WATER, PLANT…
FOOD MICROFLORA
SOURCES OF MICROORGANISM IN FOOD
SOIL AND WATER
PLANT AND PLANT PRODUCT
FOOD UTENSIL
INTESTINAL TRACT HUMAN AND ANIMAL
FOOD HANDLERS
ANIMAL HIDES AND SKIN
AIR AND DUST
FACTOR AFFECTING MICROBIAL GROWTH IN FOOD
PARAMETER OF INTRINSIC FACTOR
INTRINSIC FACTOR :NUTRIENTS
needed protein, carbohydrates, lipid, water, energy, nitrogen, sulphur, phosphorus, vitamins, mineral for growth.
have specific nutrient that help microbial growth.
nutrient composition food influences type m/o will growth
m/o found in food full with nutrient with bacteria then follow by yeast & molds.
INTRINSIC FACTOR: WATER ACTIVITY
-relates to water present in food in free form
aw = vapour pressure of food substrate
vapor pressure of pure water same tempt
affect growth, toxin production, spore germination & heat resistance
INTRINSIC FACTOR : BIOLOGICAL STRUCTURES
B/S prevent microbial entry
example : Meat has fascia, skin, membrane to prevent
egg have shell & inner membrane to prevent yolk and egg.
INTRINSIC FACTOR : pH
bacteria growth neutral / weakly alkaline pH ( 6.8 - 7.5)
bacteria: growth narrow pH 4.5 - 9.0 ( salmonella)
yeast / molds/ bacteria grow range : mold ( 1.5 - 11.0) yeast ( 1.5 - 8.5 )
m/o inhibited by acid condition
i) exception include lactic acid bacteria
i) acid food : have natural pH 4.6 or less
ii) acidified food : low acid foods to which acid are added ( pH 4.6 or less & aw 0.85 or more)
iii) low acid food : pH greater then 4.6 & aw 0.85 or more
I
NTRINSIC FACTORS : REDOX POTENTIAL & 02
presence & absence of free oxygen, M/o have grouped
i) aerobes
ii) facultative anerobes / anaerobic ( canned food )
iii) anaerobes
iv) microaerophiles ( vaccum pack)
v) aerobic bacteria ( surface raw meat)
vi) aerobic molds ( dried / salted product )
ability to generate energy by specific metabolic reaction depend on the redox potential of food
influent by chemical composition, processing treatment, storage condition ( reltion to air )
INTRINSIC FACTORS : ANTIMICROBIAL CHEMICAL
i) MICROBISTATIC ( STOP DIVISION OF M/O)
ii) MICROBICIDAL ( KILLING M/O)
ANTIMICROBIAL EFFECT:
damaging structure of cell / function
affecting microbial enzyme
-reacting with DNA
ANTIMICROBIAL ENZYME :
very important defensive reaction between living m/o
hydolases ( basic structure of the cell
oxidoreductases ( reactive molecule, degrade vital cell protein)
EXTRINSIC FACTOR: TEMP OF STORAGE
food exposed to different tempt
PYSHROPHILIC BACTERIA
grow at 20c to -10c ( unfrozen)
can cause food spoilage at low tempt
found in soil & water
MESOPHILIC BACTERIA
grow between 25c and 40c ( optimum 37c)
pseudomonas aeroginosa grow lower 5-43c
-non mesophilic bact able to grow 5c or above 45c
THERMOPHILIC BACTERIA
grow at tempt above 45c
-optimum growth between 50c - 70c
some bacteria growth 80c
in processed food
TEMPERATURE
below freezing 0c aw avaibility decreased
water crystallizes & is unavailable
at low temt ( enzymatic action is very slow/ non existent
EXTINSIC FATORS: RELATIVE HUMIDITY OF ENVIROMENT
-relative humidity & aw interelatted
measure of aw of the gas phase
dormant spores of bacteria / fungi to germinate
EXTRINSIC FACTORS: GASEOUS IN ENVIRONMENT
oxygen influences the redox potential
carbon dioxide regulates cell growth of some bacteria
obligate aerobes ( cannot grow under anaerobic condition )
obligate anaerobes ( grow in anaerobic )
refer to food composition & character that influence microbial growth