milk quality defect
TRANSCRIPT
GROUP MEMBERS
SAJID ASLAMSAJJAD HASSAN QADEER
MUHAMMAD AFZAL SOHAILMUHAMMAD FARRUKH HAFEEZ
WHAT IS MILK ?Milk is defined as the secretion of mammary glands of mammals.I i ll h i i d i h diIt contains all the nutrients required in human diet.It is “food for life”.Milk l d l i b ildi h l h Milk plays a tremendous role in building a healthy body.It is perishable commodityIt is perishable commodity.
COMPOSITION OF MILKComponents Average content in milk
(%w/w)Range (% w/w)
Water 87.1 85.3-88.787.1 85.3 88.7SNF 8.9 7.9-10.0
Lactose 4.6 3.8-5.3Fat 4.0 2.5-5.5
Protein 3.3 2.3-4.4C iCasein 2.6 1.7-3.5
Mineral substances
0.7 0.57-0.83
(Walstra, Pieter., et al, 2006)
MILK QUALITY DEFECTSMilk defects includes all the changes in flavor, taste, and color of milk.Milk li i f i l h fMilk quality can not improve after it leaves the farm.Defects on the basis of properties
T d fTaste defectsFlavor defectsColor defects
MILK DEFECT DUE TO TASTE Defect of milk due to taste have following points
Defects due to presence of abnormal milks
Defects due to changes in milk constituents
Defect due to transmitted flavors
DEFECTS DUE TO PRESENCE OF ABNORMAL MILKS
Colostral milks or pathological milks
ABNORMAL MILKS
Colostral milks or pathological milks
Abnormal mineral
Abnormal protein composition p p
DEFECTS DUE TO CHANGES IN MILK CONSTITUENTS
Defects of microbial origin
f d f id i Defects due to fat oxidation
D f d h Defects due to heat treatment
DEFECTS OF MICROBIAL ORIGINN f b t i hi h d f t f ilk litName of bacteria which cause defect of milk qualityVegetative bacteria
Actinomyces sppActinomyces sppLactococcus lactic sppStreptococcus lactis maltigenes
Spore forming bacteria BacillusPsychrotrophicPsychrotrophic
Fungus that defect the milk quality Mold Mold Yeast
DEFECTS OF MICROBIAL ORIGIN
Highly favorable culture medium for microbial life
Taste defect due toB i l b li• Bacterial metabolism
• Complex enzyme systems• Effect of mastitis Effect of mastitis
.
BACTERIAL METABOLISM
Lactic acid production Volatile compounds productionEffect of enzyme released by bacteriaProteolysis due to extra‐cellular proteasesThermostable enzyme Lipolytic enzymes
BACTERIAL DENSITY Correlations between bacterial density and the appearance of defects have been established
When germ concentration exceeds 10⁶/ml off‐tastes can be detectedcan be detected
When the temperature rises the growth rate is When the temperature rises the growth rate is multiplied by 5.8 for every 10°C rise.
EFFECT OF MASTITIS
Shedding of somatic cell
Lipolysis and casein hydrolysis will increase
DEFECTS DUE TO FAT OXIDATION
Effect of oxygen on the milk phospho‐lipids
Presence of contaminant metal traces
DEFECTS DUE TO HEAT TREATMENTTREATMENT
Salt toward insoluble forms
Decomposition of the lactose
Intense heating the fat produces lactone and methyl ketone
DEFECTS DUE TO TRANSMITTED FLAVOURS
Its high water and lipid contentPresence of foreign chemical substances Feed cause of unpleasant tasteChemical flavors
FLAVOR OF MILKFresh milk has a mild, pleasing and slightly sweet and rich flavor
Milk sugar
Richness by the fat
FACTORS AFFECTING THE FLAVOR OF MILKOF MILK
Feed or Weed FlavorUnclean Cowy‐Barney FlavorRancid FlavorO idi d lOxidized FlavorMalty FlavorHi h A id FlHigh Acid FlavorForeign FlavorS li htSunlight
FEED OR WEED FLAVORFEED OR WEED FLAVORFeedstuff consumedFeedstuff consumedTime dependentQuantities of feedQuantities of feed
Feed Amount fed (lbs) Time fed before milking (hrs)
Effect on milk flavor
Alfalfa ‐ green hay 5 2 Strong feed flavor
Alfalfa ‐ silage 20 1 Strong feed flavor
Oats 30 1 Very slight feed flavor
Soybean ‐ green 30 1 Slight improved flflavor
Turnip 15 1 Strong feed flavor
UNCLEAN COWY‐BARNY FLAVOR
Contributing factors
Poorly ventilated barn
Dirty cows are milked
Improperly cleaned and sanitized milk‐handling equipmentequipment
RANCID FLAVORRANCID FLAVOR
Sharp, unclean, astringent taste
Contributing Factors
• Fat globules• Enzyme• Enzyme• Excessive agitation of warm milk in the presence of air
OXIDIZED FLAVOROXIDIZED FLAVOR
Tallowy, metallic or cardboard like off‐flavor
Contributing Factors
metals contaminating milk (i.e. copper pipe). Hi h f f d (i b d) High fat feeds (i.e. soybeans, cottonseed) lack of antioxidants feed rations
MALTY FLAVORMALTY FLAVOR
Milk has a malty or grape nut like flavor
Contributing Factors
• Bacterial growth
• Contamination of milking machines and other milk handling equipment
HIGH ACID FLAVORHIGH ACID FLAVOR
The milk has an unpleasant, disagreeable odor and sour taste.Contributing Factors
• milk is heavily contaminated with bacteria and the bacteria is permitted to grow.g
FOREIGN FLAVOR• flavor of milk which has absorbed or been contaminated with chemicals.
Contributing Factors• medications disinfectants sanitizers fly sprays gasoline and other petroleum • medications, disinfectants, sanitizers, fly sprays, gasoline and other petroleum
products
SUNLIGHTSUNLIGHT
Burnt‐protein or burnt‐feathers‐like, "medicinal"‐like
C t ib ti F tContributing Factor
This defect is caused by UV‐rays from sunlight or This defect is caused by UV‐rays from sunlight or fluorescent lighting catalyzing oxidation in unprotected milk.Photo‐oxidation activates riboflavin which is responsible for catalyzing the conversion of methionine to methanol.
MILK DEFECT IN UDDER
Fishy milk Rancid milkSlow creaming milkPremature curdlingGritty milkFlaky milk
MILK DEFECT WHEN MILK DRAWNMILK DEFECT WHEN MILK DRAWN FROM UDDER
Bitter milkRopy milkSoapy milkFailure to sour and “butter”Turnip like taste
DEFECT OF COLOURBlue milkRed milkYellow or Orange milkYellowish milkGreenish Yellow milkViolet milk
CONCLUSIONClean and sanitize all milking equipments
Check ventilation in feeding and housing areasC g g
Keep floors, walls, ceilings clean
Lower the load of pathogen as possible
Milk samples should be tested regularly
Maintain milk quality by keeping the herd SCCq y y p g
REFERENCESSHARIF, A., AND MUHAMMAD, G., Somatic cell count as an indicator of udder health status under, REVIEW ARTICLE Pakistan Vet. J., 2008, 28(4): 194-200.Sharif, A., T. Ahmad, M. Q. Bilal, A. Yousaf and G. Muhammad, 2007. Effect of severity of subclinical mastitis on somatic cell count and lactose contents of buffalo milk. Pakistan Vet. J., 27: 142- 144.Santos, M.V., et al, Sensory Threshold of Off-Flavors Caused by Proteolysis and Lipolysis in Milk, American Dairy Science Association, 2003. J. Dairy Sci. 86:1601–1607McSweeney, P.L.H., H.E. Nursten, and G. Urbach. 1997. Flavours and off-flavours in milk and dairy products. Pages 403-411 in Advanced Dairy Chemistry Volume 3: Lactose, water, salts and vitamins. 2nd edition P.F. Fox, ed. Chapman & Hall, London, UK