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

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•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

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Temperature

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The Effect of Temperature

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Oxidation- Reduction potential

O-R PotentialEh- mV

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•Oxygen

•Aerobe - Eh positive

•Anaerobe – Eh negative

Environmental Factors

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•Oxygen

•Oxygen readily accepts electrons (reduced)

•Electrons come from cellular components (oxidized)

Environmental Factors

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•Oxygen

•Aerobic organisms produce enzymes to destroy oxygen free radicals

Environmental Factors

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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

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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

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Biological structure

Shell

Fat layer

Skin

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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

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Butryic or Butyric acid bacteria

Clostridium

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Propionic or propionic acid bacteria

Propionibacterium

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Proteolytic bacteria

Bacillus

Pseudomonse

Clostridium

Proteus

Streptococcus, Micrococcus Acid proteolytic

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Lipolytic bacteria

Pseudomonase

Alcaligenese

Staphylococcus

Serratia

Micrococcus

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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

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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