milk powder (2).ppt

milk powder

1. MILK POWDER
Dr. AYSHA SAMEEN

2. MILK POWDER
•Milkpowderisproducedonlargescalein
modernplants
•Skimmilkpowderhasmaximumshelflifeof
aboutthreeyears
•Wholemilkpowderhasmaximumshelflifeof
aboutsixmonths
•Fatoxidisesduringstorage,witha
consequentgradualdeteriorationintaste

3. Drying
•Dryingmeansthatthewaterinaliquid
product-inthiscasemilk-isremoved,so
thattheproductacquiresasolidform.
•Thewatercontentofmilkpowderranges
between2.5and5%
Benefitsofdrying:
•Reducestheweightandvolume
•Reducesthetransportationandstoring
cost.
•Freezedrying-thewaterisevaporated
undervacuum

4. FreezeDrying
•Thismethodofferadvantagesfromquality
aspects,astheproteinfractionisnotaffected
•Freezedryingisnotusedwidelybecauseof
highenergydemand
Twoprincipalmethodusedindairyindustry
•Rollerdrying
•Spraydrying
Inthismethodtwostages
1.Concentrationbyevaporation
2.Dryinginspraytower

5. USES OF MILK POWDER
•RECOMBINTION OF MILK
•Mixing into dough in bakery industry
–To increase the volume of bread
–Improve its water binding capacity
–Bread will remain fresh for longer time
•Mixing into pastry dough to make it crisper
•Substitute for eggs in bread and pastries
•Producing milk chocolate in chocolate industry
•Used in sausages
•Substitute for mothers milk in baby foods
•Production of ice cream
•Animal feed

6. Skimmed milk powder
•Mostcommontypeofmilkpowder
•Applicationmakesitspecificdemandonmilk
powderforexampleforrecombinedmilk
–Easilysoluble
–Correcttaste
–Nutritivevalue
•Somedegreeofcaramellisationoflactoseis
beneficialinchocolateproduction
•Forrecombinedmilkgentledryingofproductin
aspraytowerisessential
•Forchocolatepowdermaybesubjectedto
intenseheattreatmentinarollerdryer

7. Skimmed milk powder
•Twotypesofpowderare
1.Rollerdryerpowder
2.Spraydryerpowder
•solubilityofspraypowderisverygoodwhereasthat
ofrollerdryerpowderisappreciablypoor
•Dependingonintensityofheattreatmentmilk
powderisclassifiedintocategories
•Extralowheat
•Lowheat
•Mediumheat
•Mediumhighheat
•Highheat

9. Whole milk powder
•Spray dried whole milk powder is normally
produced from standardized milk.
•Whole milk powder, unlike skim milk powder, is
not categorised.
•Milk intended for whole milk powder is
pasteurized at 80 –85 °C
•To inactivate most of the lipolytic enzymes
•That would otherwise degrade the milk fat during
storage.

10. Instant-milk powder
•Special methods for the production of both skim
milk and whole milk powder with extremely good
wet ability and solubility known as instant powder
•This powder is agglomerated into larger
particles
•A number of particles are combined to form a
larger grain (agglomerate).
•The average grain size of the product increases.

11. Instant-milk powder
•instant powder, as it is known, dissolves instantly,
even in cold water.
•Bulk density
•Bulk density is the weight of a unit volume of
powder; in practice it is expressed as g/ml, g/100
ml or g/l.
•During shipping over long distances, it is
important that they have a high bulk density as the
reduced volume saves on transportation costs and
packaging.

12. Production of milk powder
Roller drying
•In the production of roller-dried powder, the pre-
treated milk is fed to a roller dryer after evaporation
and the whole drying process takes place in one stage.
Spray drying
•In the production of spray-dried powder, the milk is
first evaporated in a vacuum evaporator to a DM
content of 48 –50 % and then dried in the
spray tower.

14. Raw material
•Very strict demands are made of the quality of the
raw material for the production of milk powder.
•Spray powder production involves vacuum
evaporation, it is very important to keep heat-
resistant bacteria under control so that they cannot
multiply during evaporation.
•Bactofugation or microfiltrationof the milk can
therefore partly be used to remove bacteria spores
from the milk,

15. Raw material
•Milk for powder production must not be
subjected to excessive thermal impact prior
to evaporation and drying.
•This could denature whey proteins and there
by impair
1. solubility
2. aroma and flavour of the milk powder.

16. Raw material
•The milk is subjected to a peroxidase test or
a whey protein test to determine the degree
of heat treatment.

17. General pre-treatment of the milk
•In the production of skim milk powder, the
milk is clarified in conjunction with fat
separation.
•Whole milk and skim milk are pasteurised
at various temperatures depending on the
powder quality requirements.

18. Roller drying
•In roller drying, the milk concentrate is
distributed as a film on rotating,steam-
heated drums or rollers.
•The water in the concentrated milk
evaporates, and the vapour is drawn off.
•The pre-treated milk is applied to the hot
roller surface as a thin film.

19. Roller drying
•The dried milk is scraped off the rollers and
removed by means of a screw conveyor, at which
point the milk is broken down into flakes.
•The flakes are then transferred to a grinder which
is used to create the desired grain size.
•After that, hard and burned particles are sifted off.
•Depending on the desired capacity, the roller dryer
is 1 –6 m long and has a roller diameter of 0,6 –3
m.

21. Roller drying
•Roller dryer performance is dependent on
1.Milk film thickness,
2. Roller surface temperature
3. Roller speed and
4. The DM content of the supplied milk.

22. Spray drying
•Powder production is carried out in two
phases.
•In the first phase, the pretreated milk is
evaporated to a DM content of 48 –52 %.
•Whey is concentrated to a DM content of 58
–62 %.
•In the second phase, the concentrate is
turned into powder in a spray tower.

23. Spray drying
•Spray drying is multiple-stage process:
•Atomization of the concentrate into very fine droplets in a hot
air stream
• Water evaporation
• Separation of the powder from the drying air
•Without prior concentration
–Powder particles will be very small
–Have a high air content
–Poor wetability
–Short shelf life.
–Process would also be extremely un economical

24. Basic drying installations
•Single-stage drying
•The simplest installation for producing a
powder consists
–drying chamber
–atomisation system,
–air heater,
–system for collecting the finished powder from the
dry air
–fan which sucks the necessary amount of air
through the entire system.

25. Operating system of spray drying

26. NOZZELS FOR
ATOMIZATION

27. CONTINUED…………..
•The pressure at the nozzle determines the particle
size.
•At high pressures, up to 30 MPa, (300 bar), the
powder will be very fine and have a high density.
•At low pressures, 5 –20 MPa, (50 –200 bar),
larger particleswill be formed and the fines
content will be lower.
•The pressure is built up by means of multi-
plunger high-pressure pumps.

28. Operating system of spray drying
•The concentrate is fed via a high-pressure
pump to an atomization system
•System produces very small droplets, 40 –
125µm
•The drying air is normally sucked through a
pre-filter and fine filter and then passes an
air heater
•The air is steam-heated up to 190 –200 °C

29. Operating system of spray drying
•An indirect heat recovery system can be
provided to improve energy economy
•The hot air flows through a distributor
which ensures that
–the air is traveling at a uniform speed into the
drying chamber, where it
–is mixed with the atomisedproduct in the
straight flow.
•The free water evaporates immediately
when the atomized product enters the
drying chamber.

30. Operating system of spray drying
•Surface water evaporates very quickly, as does the
moisture from the inside of the droplets which
quickly reach the surface by capillary action.
•Then heat is transferred into the particles by
convection.
•The evaporation of the water from the droplets leads to a
considerable
–reduction in weight, volume and diameter.
•Under ideal drying conditions,
–weight will decrease by about 50 % and the volume by
about 40 %.
•The diameter is reduced to 75 % of the droplet size after
leaving the atomizer,

31. Operating system of spray drying
•During the drying process, the powder
settles in the bottom cone of the chamber
and is discharged from the system
•It is conveyed to a silo or packing station by
a pneumatic conveyor which uses cold air to
cool the hot powder.
•The powder is then separated from the
transport air by means of a cyclone.