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)