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MILK BASICS. Chemical components. Milk composition. LIPIDS. Organised into globules (1-10 μ m ) having membranes of phospholipid-protein complexes 200 kinds of fatty acids - PowerPoint PPT Presentation

Transcript of MILK BASICS


  • Chemical components

  • Milk composition

    Water %Dry mat(%)Fat(%)Proteins(%)Lactose(%)Minelars(%)


  • LIPIDSOrganised into globules (1-10 m ) having membranes of phospholipid-protein complexes200 kinds of fatty acidsFatty acids of saturated (palmitic, myristic, stearic, butyric, etc.), mono- and polyunsaturated (oleic, palmitoleic, linoleic, linolenic, etc.)Holstein:3.3-3.4%, Jersey: 4.5-4.6 %


    Casein%Whey protein%cow8218sheep8020goat8020buffalo8515pig4060horse4555dog5050human4060

  • Caseins

    Caseins (1, 2, , )Colloidal micelles (0.12 m)Submicelles are bound together by calcium phosphate and, organised into spherical particles of micelles (20-300 nm)(-casein at the surface of micelles)Rennin or

  • Whey proteins

    Remaining in milk after precipitating casein (include proteose-peptonesAlbumin and lactoglobulinSerum albuminGlobulinImmunoglobulinsLactoferrin and lactoglobulins (synthesis in mammary gland),Serum albumin and immunoglobulins are from blood

  • EnzymesLipaseIn fresh milk: inactiveIn cream: concentratedInactivation at 70 C, pH optimum: 7,6-7,8AmylaseIn fresh milk: lowDuring storage activity detection of freshness52-56 C, 30 minProteaseOnly raw milk, longer storage at 37-42 C temperature.Pastuerised milk putrid tasteClostridium, Achromobacter spp. cheese production

  • Enzymesperoxidase 75 C 2,5 min, 85 C 1-2 s flash pasteurizationalkaline phosphatase 62 C 30 min, 72 C 15 s pasteurizationxanthine oxydase Cow milk , human ( Schrdinger reaction)CatalaseActivity Mastitis: activity

  • Composition and propertiesCarbohydratesLactose4.7-4.8 % (mastitis)80 Clactocaramell (taste of boiled milk)Lactobacilli lactic acidMinerals, micro-macroelements0.7-0.9 %Mastistis: Na, Cl , K, Ca, Mg, P

  • Avarage minerals and microelement content of cow milk


  • Trace elements1 g 5 mg/litreVitaminsA, B12, E, K, D3, CThiamine, riboflavin, nicotinic acid, panthothenic acid, pyridoxine, biotin, folic acidConcentration is depending on species, age, stage of lactation, nutrition, environment, etc.Sensitivity to light, air, metals, acid, etc.

  • Structure of milk

    Polydisperse structure of milk Milk as polydisperse system consits of:Dispersing medium of water Emulsified fatCollodial proteins

  • Biological componentsSomatic cell 400 0070-80 % tissue originBlood origin (granulocyte, lymphocyte, monocyte)Microorganisms104

  • Physical properties of milk

    Freezing point: -0.5 CColourNormal: bluish-white (golden-yellow), depending on breed, feed, lactation period, etc. (white: fat globules, collodial components; bluish: after removing fat; yellow: carotene)TasteNormally, slightly sweet, pleasent (lactose and chlorine)Fat and protein give the body to the flavourConsistency (substance) of milkNormal milk is a watery liquid

  • Microbiology of raw milkMilkHigh aw, neutral pH, Rich in nutritional materialsAntimicrobial substancesLactoferrinFe binding, bacteristatic effectAgainst Gr- bacteriaLactoperoxidaseAgainst Gr- bacteriaLysosymeMuramidaseAgainst Gr+ bacteria

  • Source of bacterial contamination of the raw milk

    SourceCell/mlMicrobesHealthy udder100-500Micrococcus, Staphylococcus, Streptococcus, LactobacilliSubclinical mastitis104-105Staphylococcus, StreptococcusSkin of the udder102-104Micrococcus, Staphylococcus, Streptococcus, Lactobacilli, coliforms, pathogensAir of stable102Aerobe sporesMilking machine, tubes103-106G-, Pseudomonas, eneterobacteria

  • Microflora of fresh milk

    Micro-organismOccurence (%)Micrococcus, Staphylococcus30-99Streptococcus,, Lactococcus0-50Microbacterium, Lactobacillus

  • Bacterial growth in fresh milk

    Milk is sterile at time of secretion from glandular cells (healthy uddder)Contamination is inevitable (quantity and composition; aseptically: micrococci, streptococci)Aseptically drawn milk: 100-1000 bacteria/mlDrawn under clean conditions: 1000-10000 bacteria/mlFollowing milking, rate of growth: number&type of bacteria and temperatureDrawn clean (1000-10000 bacteria/ml): doubles in 24-48 hours and reaches next decimal in 72-96 hours at 4 C. At 10 C storage, it reaches 1 decimal in 24 hours and 2-3 decimals in 48 hours.Psychrotropic microorgansisms (e.g. Pseudomonas fragi) are present in fresh milk (sources: unsterilized utensils, milking machines, water supply, dust. Off-flavours: fruity, bitter, sour, oxydised.

  • Microbiological requirements of raw milk (853/2004 EC)

    Raw cow milkOther species raw milkTotal count 30 C/ml100 000 1 500 000Somatic cell/ml 400 00 500 000Antibiotic residues MRL MRL

  • Mastitis

  • Mastitis Milk hygiene

    Milk drawn from healthy mammary gland contains 3-400000 cells/cm3Mastitis is caused by mechanical, chemical or bacterial influencesCells in milkFrom mammary gland: epithelial cells,From blood: granulocytes, lymphocytes, mononuclear cells (macrophages, giant cells)Cell content changes: systemic disease, mechanical influences including (machine) milking, physiological conditions, feeding, housing, stressSomatic cell count in healthy udder is 30% and it may be increased up to 95% in mastitis

  • Changes of somatic cell during mastitis

    Healthy milkSubclinical mastitisClinical mastitisCell number2 x 104-105/ml>5 x 105 /ml>106Neutrophyl gr.22%>22 %70-98 %Lymphocyte 8 %8 %16% (>40 %)

  • MastitisSomatic cell Plasma proteins Bovine serum-albumin (BSA) alpha-antitrypsineIon concentrationNa, Cl ( together with the electrical conductivity ) Intracellular enzymesN acetyl-glucose-aminidase (NaGase)Epithelial cell secretionLactose, fat, casein,

  • Methods for cell detectionIndirect testMastitestWhiteside-testQuantitative method

  • Microbes causing mastitis

    SOURCE OF INFECTIONFrom animal to animalFrom enviroment to the udderMAJOR MICROBES CAUSING MASTITISStreptococcus agalactiae, dysgalactiae, uberis, pyogenes animalis, faecium, faecalis, pyogenes humanusStaphylococcus aureusEscherichia coliKlebsiella pneumoniaePseudomonas aeruginosaAlgae, fungi

  • Contagious pathogensFrom the infected udderDuring milking, teat cup, rubber, Cow, calfStaphylococus aureus, streptococcus agalactiae, Corynebacerium bovis, Mycoplasma bovis and other Mycoplasma spp., Streptococcus dysgalactiae

  • Staphylococcus aureusSkin of the animal, teat cup, rubber, End of milking(Hand of the workers)Alveolar epithel cells destroyed Subclinical (common), clinical formWatery, flakes,

  • Staphylococcus aureusThe incidence of staphylococcal mastitis is increasing (as incidence of streptococcal mastitis decreasing). About 1-1.5 million staphylococci per gram of food must be present for producing sufficient amount of enterotoxin required to induce symptoms in man. Below 10 C, no growth and no toxin production take place. The toxin is heat-stable. Symptomless humans carry the causative in the nose, and skin but the udder and skin of dairy animal is also infected (human origin). Milkworkers with cuts, boils and other lesions on hand should not be allowed to handle milk or milk products. The main-line of protection, however, is to prevent the growth of staphylococci by cooling below 8 C as soon as possible.

  • Streptococcus agalactiaeTypically from animal to animalMilking!No serious clinical symptomsRRarely

  • ListeriosisListeria monocytogenes was isolated from milk and one of the vehicles of the infection (to humans) is considered to be milk. The organism is able to grow in milk at ambient temperatures. The control of milk-borne infection with Listeria depends on adequate heat-treatment: 72 C for 15 sec is sufficient. Many cases of human listeriosis occurred in the last years following the consumption of different types of soft cheeses which are made from raw milk.Sheep!

  • Enviromental pathogensStreptococcus uberis and other fecal streptococciIntestineLactoperoxidase

  • ColiformsE. coli and KlebsiellaEndotoxin, mastitisAcute, peracute alveolar mastitisMilk amountWatery, yellow-withish flakes

  • Algae, fungiAlgaePrototheca zopfiiChronic or subclinical mastitisFungiDue to widespread use of antibiotics in mastitis may lead to increase in incidence of mycotic mastitis. No direct evidence for milk-borne infection to man.Nocardia asteroides and braziliensis, Candida tropicalis, albicans, krusei were isolated from mastitic udder and from milk. They may survive usual pasteurization processes