ENVIRONMENT
FEEDING
BREEDING
HOUSING MANAGEMENT
HEALTH
HYGIENE
MILKING
CONTAMINATIONRETAINING QUALITY
BASIC REQUIREMENTS FOR “OPTIMUM PRODUCTIVITY”
Microbiological Spoilage of Dairy Products
Microbes in raw milkMicrobes in raw milk
Three basic sourcesThree basic sources From within the udderFrom within the udder From exterior of teats and From exterior of teats and
udderudder From milk handling and From milk handling and
storage equipmentstorage equipment
Factors AffectingFactors Affecting
Duration of milk storage-Duration of milk storage-time vary widelytime vary widely
Udder-diseases-mastitis Udder-diseases-mastitis associated micro-associated micro-organismsorganisms
Factors influencing Factors influencing microbiological quality of microbiological quality of
raw milkraw milk Initial micro floraInitial micro flora Bio-security, udder diseases and Bio-security, udder diseases and
bacterial contentbacterial content Pathogens for man in raw milkPathogens for man in raw milk Environmental sourcesEnvironmental sources Micro flora of milking equipmentMicro flora of milking equipment Influence of storage and transportInfluence of storage and transport
Microbial CountMicrobial Count
Vary:< 1000 to >10Vary:< 1000 to >1066 /ml /ml (SPC)(SPC)
Not exact estimate of Not exact estimate of total bacterial contenttotal bacterial content
Types of MicrofloraTypes of Microflora
Heterogeneous population-Heterogeneous population-mesophilic, thermoduric, mesophilic, thermoduric, thermophilic, psychrotrophic thermophilic, psychrotrophic and pathogenic organismsand pathogenic organisms
Presence/relative Presence/relative proportions vary with the proportions vary with the conditions of milk conditions of milk production and handling. production and handling.
Cultivation conditions Cultivation conditions
Psychrotrophs: incubation at Psychrotrophs: incubation at 5°-7°C for 10 days5°-7°C for 10 days
Thermodurics: after Thermodurics: after pasteurizing milk samplepasteurizing milk sample
Other groups: selective media Other groups: selective media coliforms, lactic acid coliforms, lactic acid bacteria, Gram-negative rods, bacteria, Gram-negative rods, pathogenic organisms, etc.pathogenic organisms, etc.
Mesophilic MicrofloraMesophilic Microflora
Growth temp. >30°C in 2-3 days Growth temp. >30°C in 2-3 days (less than 5,000 cfu/ml) (less than 5,000 cfu/ml)
Micrococci & Staph. 30-90%Micrococci & Staph. 30-90% Streptococci 0-50%Streptococci 0-50% Asporogenous Gram+ve rods <10Asporogenous Gram+ve rods <10 Sporogenous Gram+ve rods <10Sporogenous Gram+ve rods <10 Gram-ve rods (including Gram-ve rods (including
coliforms) <10 coliforms) <10 Miscellaneous <10Miscellaneous <10
Thermoduric MicrofloraThermoduric Microflora
Survive pasteurization Survive pasteurization (can’t grow at (can’t grow at pasteurization temp.)pasteurization temp.)
Count varies widely & Count varies widely & most do not multiply most do not multiply faster at ambient temp.faster at ambient temp.
Thermoduric microbes in Thermoduric microbes in raw milkraw milk
Microbacterium (100%)-milking Microbacterium (100%)-milking equipmentequipment
Bacillus (spores)-teat surface Bacillus (spores)-teat surface (bedding)(bedding)
Clostridium (Spores)-Silage & beddingClostridium (Spores)-Silage & bedding Micrococcus-(less) milking equipmentMicrococcus-(less) milking equipment Alcaligenes1-10%Alcaligenes1-10% Others (Streptococci, lactobacilli, Others (Streptococci, lactobacilli,
coryneforms)coryneforms)
Thermophilic Microflora Thermophilic Microflora
Readily grow at 55°C to 70°CReadily grow at 55°C to 70°C Standard method incubate at Standard method incubate at
55°C55°C Grow at pasteurization temp.Grow at pasteurization temp. Facultative thermophiles grow Facultative thermophiles grow
at 37°C or lower (SPC analysis)at 37°C or lower (SPC analysis)
Thermophilic bacteriaThermophilic bacteria
Soil, bedding, feeds & water Soil, bedding, feeds & water supplies supplies
Increases if raw milk stored Increases if raw milk stored under warmer ambient conditions under warmer ambient conditions
Aerobic or facultatively anaerobic Aerobic or facultatively anaerobic spore formers Bacilli (spore formers Bacilli (B. B. stearothermophilus, B. circulans, stearothermophilus, B. circulans, B. thermoaciduransB. thermoacidurans),), Lactobacillus thermophilus Lactobacillus thermophilus (also (also in genus in genus BacillusBacillus).).
Psychrotrophic Psychrotrophic Microflora Microflora
Grow at refrigeration temp. (2° - Grow at refrigeration temp. (2° - 7°C)7°C)
Majority mesophilicMajority mesophilic Optimum growth temp. 20° to Optimum growth temp. 20° to
32°C32°C Detected at 5°-7°C in 7-10 daysDetected at 5°-7°C in 7-10 days Gram-negative rods & Gram-Gram-negative rods & Gram-
positive rods or coccipositive rods or cocci..
PsychrotrophsPsychrotrophs
Gram-negative rodsGram-negative rods are are common in fresh raw milkcommon in fresh raw milk (10-15% of the initial (10-15% of the initial microbial count)-microbial count)-Genera Genera Pseudomonas, Acinetobacter, Pseudomonas, Acinetobacter, Flavobacterium, Flavobacterium, Achromobacter, Alcaligenes Achromobacter, Alcaligenes and Enterobacterand Enterobacter (coliforms). (coliforms).
PseudomonasPseudomonas 50% of Gram-negative rods 50% of Gram-negative rods
are are Ps. fluorescens Ps. fluorescens (predominant),(predominant), Ps. putida, Ps. putida, Ps. fargi, Ps. aeruginosaPs. fargi, Ps. aeruginosa etc. etc.
Produce heat stable enzymes Produce heat stable enzymes (lipases and proteinases) in (lipases and proteinases) in refrigerated milkrefrigerated milk
Pseudomonas-Cont..Pseudomonas-Cont..
Vegetative cells killed at Vegetative cells killed at pasteurizationpasteurization
Produce Enzymes-Produce Enzymes-responsible for fat & responsible for fat & casein degradationcasein degradation
Source-improperly cleaned Source-improperly cleaned milking equipmentmilking equipment
Gram-positive-Gram-positive-psychrotrophspsychrotrophs
Gram-positive rods & cocciGram-positive rods & cocci Bacillus spp. (Bacillus spp. (B. B.
coagulans, B. circulans & coagulans, B. circulans & B. subtilisB. subtilis))
Arthrobacter spp.Arthrobacter spp. Streptococcus spp.Streptococcus spp.
Coliform (mainlyColiform (mainly Enterobacter Enterobacter spp.)spp.)
Aerobic & facultative anaerobic, Aerobic & facultative anaerobic, Gram-ve Non-spore forming rodsGram-ve Non-spore forming rods Ferment sugar lactose (acid & Ferment sugar lactose (acid &
gas) at 32°C in 48 hgas) at 32°C in 48 h 10-13% of the psychrotrophs in 10-13% of the psychrotrophs in
raw milkraw milk Escherichia, Enterobacter Escherichia, Enterobacter
((AerobacterAerobacter) & ) & KlebsiellaKlebsiella
Presence of coliformsPresence of coliforms
Index of direct faecal Index of direct faecal contamination (in water but not contamination (in water but not in milk)in milk)
Other sources-improperly Other sources-improperly cleaned milking equipment cleaned milking equipment (moist, milky residues allow (moist, milky residues allow multiplication)multiplication)
Absence-cleaned milking Absence-cleaned milking equipment not necessarily true.equipment not necessarily true.
Cont…Cont…
Also included under Also included under thermoduric microflora (in thermoduric microflora (in commercially pasteurized commercially pasteurized samples).samples).
Improperly cleaned milking Improperly cleaned milking equipment & psychrotrophic equipment & psychrotrophic Gram-negative rods (derived Gram-negative rods (derived from animal’s teat also)from animal’s teat also)
Pathogenic microbes in Pathogenic microbes in raw milkraw milk
Gain entry into raw milkGain entry into raw milk• Co-secretion into milk as a Co-secretion into milk as a
result of diseased animal or result of diseased animal or its udderits udder
• Contamination of milk from Contamination of milk from infected human handlers, infected human handlers, faecal and non-faecal faecal and non-faecal sources, etc.sources, etc.
Pathogenic microbes in Pathogenic microbes in raw milk raw milk
Brucellosis (Brucellosis (Brucella abortus, Br. Brucella abortus, Br. melitensis, Br. suismelitensis, Br. suis))
Tuberculosis (Tuberculosis (Mycobacterium Mycobacterium tuberculosis or M. bovis)tuberculosis or M. bovis)
MastitisMastitis Frequently-Frequently-Strept. agalactiae, Staph. Strept. agalactiae, Staph.
aureus, E. coliaureus, E. coli Infrequent-Infrequent-Listeria monocytogenes, Listeria monocytogenes,
L. icterohaemorrhagiae, B. cereus, Cl. L. icterohaemorrhagiae, B. cereus, Cl. Perfringens, P. multocida, Perfringens, P. multocida, Actinomyces & Coxiella burnetiiActinomyces & Coxiella burnetii
Cont..Cont..
Faecal contamination- Faecal contamination- Salmonella Salmonella typhi, Sal. Paratyphityphi, Sal. Paratyphi
Human handlersHuman handlers (infected/carriers)(infected/carriers) Sal. Sal. Schottmuelleri, Sal. hirschfeldii, Schottmuelleri, Sal. hirschfeldii, E. coli, Vibrio cholerae, Shigella E. coli, Vibrio cholerae, Shigella dysenteriae, Sh. Flexneri, dysenteriae, Sh. Flexneri, Streptococcus pyogenesStreptococcus pyogenes
Rodents Rodents Streptobacillus Streptobacillus moniliformismoniliformis
Pathogens- cont..Pathogens- cont..
Bovine mastitis(infrequent)-Bovine mastitis(infrequent)-yeast yeast Cryptococcus Cryptococcus neoformansneoformans
Viruses Adenoviruses, Viruses Adenoviruses, Enteroviruses, Hepatitis virus Enteroviruses, Hepatitis virus (Human handlers)(Human handlers)
Tick-borne encephalitis virus Tick-borne encephalitis virus & FMD (milch animals)& FMD (milch animals)
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