food microbiology food microbiology book, dr. frazier
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FOOD Microbiology
Food Microbiology book ,
Dr. Frazier
Objective :
Introduction to food microbiology
Important factors in food which influence in bacterial growth
Dr. H. Gh. Safaei
Composition of the Microbial World:- Procaryotes: simple morphology and lack true membrane delimited nucleus
- Eucaryotes: morphologically complex with a true membrane enclosed nucleus
Dr. H. Gh. Safaei
Review of Microbiology
Mostly Single Cell
Groups
Morphologies
Gram Reactions
Size
Growth Rate
Microorganism
Dr. H. Gh. Safaei
Application of Microbiology
Dr. H. Gh. Safaei
-Medicine, agriculture, Food science, ecology, genetics, biochemistry, immunology, and many other fields.
Virologist, Bacteriologist, Parasitologist, Mycologist, Phycologist
مواد اهدافمیکروبشناسیغذایی
از و غذایی مواد فساد از جلوگیرییا میکروبها وسیله به انها رفتن بین
انها سمنگهداری برای بهتر روشهای ارائه
غذایی موادمفید میکروبهای از استفاده
ومسمومیتها کاهشعفونتها
Dr. H. Gh. Safaei
Important factors in food which influence in bacterial growth
1.PH2.aw
3.Oxidation- reduction potential4.Nutrient content5.Inhibitors6.Biological structure
Dr. H. Gh. Safaei
•PH
• H+ concentration
Environmental Factors
Dr. H. Gh. Safaei
•PH
•Acidophiles
•Neutrophiles
•Alkalophiles
Environmental Factors
Dr. H. Gh. Safaei
Acidophilesgrowth optimum between pH 0 and pH 5.5
Neutrophilesgrowth optimum between pH 5.5 and pH 7
Alkalophilesgrowth optimum between pH8.5 and pH 11.5
Dr. H. Gh. Safaei
Microorganism Minimum PH Maximum PH
E.Coli 4.4 9
Salmonella typhi 4.5 8
Streptococcus lactis
4.3 4.8
Molds 1.5 11
Yeast 1.5 8.5
Dr. H. Gh. Safaei
PH (Hydrogen ion Concentration)
Minimum, Optimum, Maximum PH
Molds &Yeast more resistant than Bacteria
Different foods have different PH
Mold > Yeast > Bacteria
PH meter
Dr. H. Gh. Safaei
aw water activity level
Dr. H. Gh. Safaei
Water AvailabilityPlasmolysis
Food preservation: jams, jellies, etc. Dr. H. Gh. Safaei
Calculation of aw
ratio of the water vapor pressure to the vapor
pressure of pure water at the same temperature
aw = P/P0
P= Vapor pressure of the solution
Po= Vapor pressure of the solvent (water)
Dr. H. Gh. Safaei
aw Calculation : Raoult Rule
aw = P/P0 = N1/N1+N2N1= Number of water mole = 55.5 in 1 liter
N2 = the number of solute moles
Dr. H. Gh. Safaei
R.H= Relative Humidity
E.R.H = aw x 100
Dr. H. Gh. Safaei
Pure Water aw=1.00
22% NaCl Solution = 0.86
Saturated NaCl Solution = 0.75
Dr. H. Gh. Safaei
Minimum aw for growth of spoilage organism
Spoilage Bacteria 0.91
Spoilage Yeasts 0.88
Spoilage Molds 0.80
Halophilic Bacteria 0.75
Xerophilic Bacteria 0.65
Osmophilic Bacteria 0.60
Dr. H. Gh. Safaei
Water availability
In general, lower water activity inhibits microbial growthwater activity lowered by:
dryingaddition of salt or sugar , gelatinCrystallization , Ice
osmophilic microorganismsprefer high osmotic pressure
xerophilic microorganismsprefer low water activity
Dr. H. Gh. Safaei
Pure water Temp. aw
o°C 1
-5°C 0.953
-10°C 0.907
-15°C 0.846
-28°C 0.823
Dr. H. Gh. Safaei
Bacteria Minimum aw
Pseudomonase 0.97
E.coli 0.96
Bacillus subltilus 0.95
Enterobacter 0.945
Staphylococcus areus
0.86
Clostridum botuilinum 0.93
Dr. H. Gh. Safaei
Bacteria Optimum aw
S. aureus 0.995
Streptococcus fecalis 0.982
E.coli 0.995
Dr. H. Gh. Safaei
Optimum aw for germination & sporulation of Yeast & Molds are different
Germination Min. 0.62
Dr. H. Gh. Safaei
Factors Influence on Bacterial aw
Type of Solvent
Nutrient content of culture
Temperature
Oxygen
PH
Inhibitors
Dr. H. Gh. Safaei
Measurement of aw
Freezing Point
Manometric Technique
Electric technique
Dr. H. Gh. Safaei
Temperature
Dr. H. Gh. Safaei
The Effect of Temperature
Dr. H. Gh. Safaei
Oxidation- Reduction potential
O-R PotentialEh- mV
Dr. H. Gh. Safaei
•Oxygen
•Aerobe - Eh positive
•Anaerobe – Eh negative
Environmental Factors
Dr. H. Gh. Safaei
•Oxygen
•Oxygen readily accepts electrons (reduced)
•Electrons come from cellular components (oxidized)
Environmental Factors
Dr. H. Gh. Safaei
•Oxygen
•Aerobic organisms produce enzymes to destroy oxygen free radicals
Environmental Factors
Dr. H. Gh. Safaei
Dr. H. Gh. Safaei
Oxidation- reduction Potential
Balance O-R is destroyed by :
Heating
Destroy oxidative agent
Fast distribution of oxygen
Change the physical structure
Processing
Oxygen concentration
Dr. H. Gh. Safaei
Nutrient Content
Foods for Energy production
Foods for growth
Accessory element - Vitamins
Dr. H. Gh. Safaei
Inhibitors
Inhibitors : Naturally ( lactinin , Anticoliform in fresh milk, Lysosome in White egg , Acid benzoic in cherry ) Accidental ( Heating of lipid leads to autoxidation , heating of sugars produce furfural Added salt , antibiotic
Dr. H. Gh. Safaei
Biological structure
Shell
Fat layer
Skin
Dr. H. Gh. Safaei
For control of bacterial growth & food preservation it is better to combine Intrinsic & extrinsic factors.
Dr. H. Gh. Safaei
Summary
PH, aw, O- R potential, Nutrient content, Inhibitors, Biological structure factors in food which influence in bacterial growth
Dr. H. Gh. Safaei
Question
• What is the application of PH &aw in food Microbiology ?• What is the meaning of facultative ?• What is the meaning of Autotrophe
and Heterotope • Two examples of inhibitors ?
Dr. H. Gh. Safaei
Microscopic :
1.Shape: Cocci, Bacillus, Coccobacilli, Vibrio, Spirochete
2.Size
3.Structure: Capsule, Spore, Flagella….
4.Gram stain
Morphological characteristic ofBacteria
Carbohydrate hydrolysis
Protein Hydrolysis
Oxidation – Reduction reaction
Physiologic Characteristic
Genus Staphylococcus ; S. aureus
Facultative
Pathogen Coagulase positive, Beta hemolytic
Enterotoxin
Gram positive Cocci
Genus Staphylococcus ; S. aureus
Facultative
Pathogen Coagulase positive, Beta hemolytic
Enterotoxin
Gram positive Cocci
Homofermentative
Lancefield Group ( A,B,C,D )
Pyogenic (S. agalactiae, S.pyogen), no10-45ºC
Viridance (S.thermophilus, S.bovis), 45ºC
Lactic (S.ceremoris, S.lactis), 10ºC
Enterococcus( S.faceium, S. fecalis), 10,45ºC
Genus Streptococcus
Thermoresistant
Salt resistant ; 6.5% or more NaCl
PH 9.6
10-45º C
Indicator organism ; Fecal contamination
Enterococci
Aerobic , Catalase positive
Carbohydrate fermentation
Simple nitrogen
Acid proteolytic
Halotolerant 25-30 ºC,Thermotolerant , Psychrophile (10ºC)
Pigment ( M.luteus yellow , M.roseus pink )
Genus Micrococcus
Beta coccus , heterofermentative
L.dextranicum , L.cremoris
Produce diacetyle
Halotolorant, L. mesenteroids
Carbohydrate fermentation in vegetables
Osmotolerant L. mesenteroids 55-60 %
Gas forming
Slime forming from sucrose , Dextran
Genus Leuconostoc
Cocci , Gram positive , Catalase positive
Microaerophil
Homofermentative, 5.5% Nacl
7-45ºC, optimum 25-32ºC
Halotolerant, Acid produce
Range tempreture ,
Genus Pediococcus
Gram positive bacilli , Microaerophil ,
Catalase negative
Homofermentative & Heterofermentative
Genus Lactobacillus
L. helveticus at 37ºC
L. lactis
L. acidopilus
L. thermophilus
L.delbruckii
L. bulgaricus
Heterofermentative L. fermentum high temperature
Homofermentative
L.casei with low temperature
L.plantarum
L.leichmanii
Heterofermentative :
L.brevis
L.hilgardii
L.trichodes
L.pastorinuc
Homofermentative
Carbohydrate fermentation
Gas forming
Vitamin indicator
Thermoduric
Important characteristic
C.diphteriae
Mastits
Genus Cornynebacterium
Gram positive Bacilli
L. monocytogenes
M. lacticum
Thermoduric
15-35ºC optimum 30ºC
Genus Listeria & Microbacterium
1. Gram positive bacilli, catalase positive
2. Anaerobe , aerotolerant
3. Carbohydrate fermentative , acid lactic , polyalcohol, acid acetic , propionic acid & co2 producing
4. Gas forming in cheese
5. Pigment producing
Genus Propionibacterium
Gram positive bacilli
20-25 ºC
PH 5-9
6.5-10% NaCl
63 ºC for 1 minutes
B.thermophacta – Meat in refrigerator
Genus Brochotrix
Endospore forming
Catalase negative
Mesophil or thermophile
Carbohydrate fermentation produce butyric acid
Proteolytic or non proteolytic
Genus Clostridium
C. thermosaccharolyticum
C. lentoputrescence
C.putrefaciens
C. perfrigenes
C.butrycum
Types of Clostridium
Endospore
Aerobe to facultative
Mesophil or thermophil
Proteolytic , Moderate or non proteolytic
Gas producing or non gas producing
Lipolytic or non lipolytic
B. Stearothermophilus
B. coagulans
Genus Bacillus
B. cereus proteolytic Sweet-curdle in milk
B. polymyxa & Acid & gas forming
B.marcerans ( aerobacilli )
B. coagulanc Acid lactic forming
B. pumilus, B. stearothermophilus , indicator organism for sterlisation
B. subtilus Sterlisation , penicillin in milk
Genus Bacillus
Genus Escherchia
Genus Klebsiella
Genus Proteus
Genus Pseudomonase
Genus Salmonella
Genus Shigella
Genus Enterobacter
Genus Erwinia
Gram Negative Bacilli
Genus Acetobacter
Genus Aeromonas
Genus Alcaligenes
Genus Altermonas
Genus Arthrobacter
Ethanol to Acetic acid
Fruit & vegetables
Genus Acetobacter
Gram negative bacilli
22-28ºC
Facultative anaerobe
A. hydrophila pathogen for human
Genus Aeromonas
Important in sea foods
Genus Alteromonas
A. viscolactis Viscosity in milk
A. metalalcaligenes slimness in cheese
Genus Alcaligenes
Endospor
H2S
D.nigrificans
Genus Desulfotomaculum
B. linens
B.Artherobacterglobiformis
Surface of cheese
Pigment producing orange
Genus Brevibacterium
Genus Vibrio
Genus Yersinia
Genus Streptomyces
Genus Campylobacter
Genus Mycobacterium
Genus Photobacterium
other Genus
Group of important Bacteria
Lactic or Lactic acid forming bacteria
Acetic or Acetic acid forming bacteria
Butryic or Butyric acid bacteria
Propionic or propionic acid bacteria
Proteolytic bacteria
Lipolytic bacteria
Sacharolytic bacteria
Pectolytic bacteria Dr. H. Gh. Safaei
Thermophilic bacteria
Psychrophic
Halophilic
Osmophilic bacteria
Pigmented bacteria
Slime or rope forming bacteria
Gas forming bacteria
Coli form bacteriaDr. H. Gh. Safaei
Lactic or Lactic acid forming bacteria
Leuconostoc
Lactobacillus
Streptococcus
Pediococcus
Dr. H. Gh. Safaei
Acetic or Acetic acid forming bacteria
Acetobacter
Gluconobacter
Dr. H. Gh. Safaei
Butryic or Butyric acid bacteria
Clostridium
Dr. H. Gh. Safaei
Propionic or propionic acid bacteria
Propionibacterium
Dr. H. Gh. Safaei
Proteolytic bacteria
Bacillus
Pseudomonse
Clostridium
Proteus
Streptococcus, Micrococcus Acid proteolytic
Dr. H. Gh. Safaei
Lipolytic bacteria
Pseudomonase
Alcaligenese
Staphylococcus
Serratia
Micrococcus
Dr. H. Gh. Safaei
Sacharolytic bacteriaPectolytic bacteria
Saccharolytic :Bacillus subtilus , Clostridium butyricum – Amylase
Pectinlytic : Erwinia,Bacillus, Clostridium , Achromobacter , Aeromonase, Arthrobacter , Flavobacterium , Molds
Dr. H. Gh. Safaei
Thermophilic bacteriaPsychrophic
Thermophilic:Bacillus stearothermophilus
Clostridium thermosaccharolyticum
Micococcus, Streptococcus, Lacotbacillus
Psychrophic: Pseudmonase, Flavobacterium, Achromobacterium, Alcalegenese, Micrococcus, Lactobacillus, Entrobacter, Arthrobacter ,Yeast, Molds
Dr. H. Gh. Safaei
Halophilic bacteria Slightly Halophil : 0.5-3% NaclPseudomonase, Moraxella, Flavobacterium, Acintobacter, Vibrio
Moderately Halophil ; 3-15% NaclBacillus, Micrococcus, Vibrio, Acintobacter, Moraxella
Exteremly Halophil ; 15-30%Halobacterium, Halococci,
Halotolrrant 5% Bacillus , Microccous, Cornybacterium, streptococcus, Closteridium
Dr. H. Gh. Safaei
Osmophilic Bacteria
Leuconostoc
Yeast
Pigmented Bacteria
Flavobacterium , Serratia, Micococcus Lactobacillus
Dr. H. Gh. Safaei
Slime forming bacteriaKelebsiella, Alcalegenes, Enterobacter, Leuconostoc , Streptococcus, Lactobacillus
Gasforming bacteria
Heterofermentative lactic acid ,Leuconostoc, lactobacillus,
Bacillus, Propionibacterium, Esherchia, Enterobacter, Proteus , Closteridium ,
Dr. H. Gh. Safaei
?Dr. H. Gh. Safaei
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