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Fat Losses in skim Milk

There are several factors, which influence the efficiency of cream separation process. Consequently the entire fat present in milk is not recovered during centrifugal separation. The percent of total fat recovered in cream from milk is referred to as skimming efficiency. The skimming efficiency is calculated by the equation given below.

                         
Skimming Efficiency (%) = (Total fat in cream)/(Total fat in milk) x 100
                                                                 
Factors affecting the skimming efficiency are listed here:

i) Temperature of milk: The temperature of milk at the time of separation should be around 37-50°C. Separation at lower temperatures results in higher fat loss in skim milk and may lead to partial clogging of the bowl due to the increased viscosity of cream.

ii) Speed of bowl: The fat loss in skim milk will be higher at lower speed of the bowl. This loss is ascribed to the insufficient centrifugal force generation.Hence, milk should not be fed in to the cream separators unless the cream separator attains its full speed.

iii) Rate of milk inflow: The flow of milk to the cream separator should be at optimum level. If the flow is at higher rate it will result in greater loss of fat in skim milk.

iv) Size of fat globules: Smaller the size of fat globules in milk higher will be the fat content in skim milk. Due to this reason, it is observed that generally cow milk and goat milk have lower separation efficiency in comparison to buffalo milk.

v) Presence of air: Greater the amount of air in milk higher will be the fat loss in skim milk. The entrapped air reduces the efficiency of hermetically sealed separators more than that of the normal cream separators.

vi) Acidity of milk: Higher acidity of milk reduces the efficiency of separators.This is mainly due to the partial coagulation of milk, which in turn, increases the sludge formation in the bowl affecting the efficiency of separation.

vii) Mechanical condition of separator: Vibration in the machine, use of deformed/dirty/scratched/rough discs and accumulation of separator slime causes increased losses of fat in skim milk.

viii) Fat percentage in cream: Production of cream containing more than 50-60% fat causes more losses of fat in skim milk.

ix) Degree of agitation and temperature of milk: Higher temperature of milk and more agitation cause higher losses of fat in skim milk.

x) Position of cream screw: As high fat in cream causes more losses the cream screw should be appropriately adjusted.

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