Separation of cream from full cream milk using the Disc- Bowl Centrifuge.
Cream is usually a dairy product containing high fat percent, which can be seen floating on the top before the homogenization process. When the milk is unhomogenized, overtime, the fat lighter in weight rises to the top. The process in the industries is completely different as they use centrifuges, normally called as separators to accelerate the creaming process. Cost of cream totally depends upon its fat content. Cream usually produced by the livestock grazing process on natural pastures normally contains some amount of natural carotenoid pigments acquired from plant materials they consume; as a result of which the cream appears a bit yellowish in colour. Cream derived from the milk of livestock fed indoors is usually white in colour as they normally are grain based pellets. There is a formula for determining the rate of sedimentation, widely known as Stokes’ law. It states that a particle moving through viscous liquid attains a constant velocity or sedimentation rate.
Equation for Stokes’ law
Vg = d2 (Pp- P1)/ 18 µ × G
Vg = Sedimentation Velocity
d2 = particle Diameter
Pp = Particle density
P1 = Liquid density
G = gravitational acceleration
µ = viscosity of liquid
1. To separate cream from full cream milk at two speed settings of the disc bowl centrifuge. 2. To evaluate sensory properties of the cream and skimmed milk. 3. To determine the throughput of the centrifuge.
Materials and Equipments:-
1 Litre and 400 ml beakers
Litre measuring cylinder
Sample cups –transparent
2 Litres full cream milk
Large Plastic bowls
1. Two batches of 1 litre of full cream milk was warmed at 37 degree C.
2. 1 litre beaker was placed beneath the lower, heavy phase, spout of the centrifuge. This usually was the point from where the skim milk exits. Right after then the 400 ml beaker was placed beneath the upper, light phase, spout of the centrifuge which usually was the exit point for the cream.
3. Before carrying out the next step, it was ensured that the tap of the milk receiving reservoir at the top of the centrifuge was in a closed position ie. Pointing N to S
4. Warmed milk weighing 1 litre was then inserted into the reservoir.
5. The motor was switched on as soon as milk was inserted and was set on the lowest speed setting by adjusting the speed setting knob.
6. As the motor speed was steady, the tap of the reservoir containing milk was then released and the stopwatch was started.
7. Portions at light and heavy liquid phases were then collected from the relevant spouts, cream and skimmed milk respectively.
8. The stopwatch was switched off as soon as the milk reservoir was empty and the time taken was noted.
9. The motor of the centrifuge was allowed to run till the flow of skimmed milk and cream was ceased.
10. The portions of skimmed milk and cream received through their relative phases were then measured and then the yield was calculated.
11. The throughput of the material was then determined in litres per hour at its respective speed setting.
12. The stages 2 to 12 were repeated using second batch of warmed milk, with the only difference being the time setting. The whole process was carried out by operating the motor on the highest speed setting.
13. The above process was followed by placing the large bowl underneath the spouts and by flushing the centrifuge using cold water just to clear the washings in the centrifuge.
14. Right after the process the whole equipment was dismantled including the reservoirs spouts, collecting funnel etc. The parts were then washed using hot water with a little detergent.
15. The cream and skimmed milk from each speed setting (i.e. High speed setting and...
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