Milk Losses in Dairy Plants

Let us look at the milk losses in dairy plant with more objectivity. You will be surprised to note that there is no standard limit fixed for milk losses that can serve as target. Only we can compare losses of similar plants for motivating the poor performing one. However, many studies have been undertaken to evaluate process wise and product wise losses. A generalized scenario is being discussed below for reference.

i. Present Scenario of Milk Handling Losses: According to available data from industries, the milk losses vary greatly. Fat loss in dairy plant varies extremely from 0.4 % to 5%. Most of the plants have fixed certain maximum tolerable limits after a long period of experience. These may vary from 1% to 2% for ideally operated plant. In our country, the handling performance is evaluated on the basis of recovering of milk solids. For example recovery of fat in the manufacture of fat rich products like butter and ghee; and total solids recovery in the manufacture of milk powder. An efficiently operated plant should account for 98% to 99% recovery.

ii. Losses During Various Stages of Processing: Let us look at various dairy operations and areas with regard to possibility of milk loss.

a) Loss of raw milk occurs during its reception, generally, in the form of spillage and leakage at unloading and loading, lid opening, grading, tilting operations,dump vat, valves, filters, unions and pipeline, raw milk chiller and raw milk storage tank. The other form of milk loss during reception would also take place due to quality deterioration on account of delay caused by machine break down, power shedding, human negligence and insufficient dock space etc. Milk loss during reception process may also occur due to improper weighing, sampling and testing. The losses in reception may vary from 0.1% to 1.01%. In developed countries it is about 0.025%. Use of different constant factor in Richmond formulae of SNF determination may be one of the factors responsible for variation in reading at receiving and sending end.

b) During processing operations, milk solid losses would be in various forms depending upon composition of milk at the point of losses. We can observe that fat rich milk will be lost if leakages are at cream separator’s cream outlet, cream pasteurizer to cream storage line, whereas at skimmed milk outlet low fat milk will be lost. Similarly, milk leaking from pasteurizer,storage tank, pipeline and packing section has the same composition. A moderate figure of 0.1% may be appropriate for good plant. However,in some plants it may be as high as 0.5%.

c) During manufacturing of milk products the milk solids are lost directly in the form of milk, cream, residue, byproduct and final product. In these area 0.5% to 1.5% losses may be considered as moderate. In cream handling, loss to the extent of 0.1% to 0.2% may occur.

d) Powder Manufacturing: Generally powder manufacturing has the milk solids loss of 1%. But in old plant, where there is no proper powder recovery arrangement or more breakdowns, the losses may be higher.

e) Packing operation: In the packing operation, losses are mostly due to over filling, spillage and failure of packing. In milk packing, the loss of 0.5 to 1.0% is general. The general reason for losses during packing is negligence, carelessness and safety margin due to stringent laws and machine sensitivity.

iii. Identification of Milk losses: Let us look at the general dairy operations involving various equipment and processes. If you walk through the entire unit operations from reception of milk through processing and packing to final dispatches, the potential areas susceptible to milk or milk solids losses would be perceived. In order to account the potential losses, these are presented in table

Table: Identification of Milk Losses in Dairy Operations

Sr.No Name of Operation	Type of Losses
1 Milk	reception Raw milk spillage, leakage, wrong weight, wrong sampling & testing Milk Souring of due to developed acidity
2 Milk storage	Raw milk, processed milk
3 Milk processing	Milk chiller, pasteurizer, pipelines, milk tank, milk packing and cold store.
4 Cream separation	Leakage at cream outlet Leakage at skimmed milk outlet Milk solids loss in slime
5 Butter manufacture	Spillage in churn loading Washings, drainage /spillage of butter milk Spillage during unloading of churn and Transferring Butter packing losses (over filling, less overrun, spillage)
6 Ghee manufacture	Spillage in loading of P.S. Vat, Ghee Boiler, clarifier, settling and storage tank Packing losses in the form of over filling, leakage and non-recovery from damage packs.Losses through ghee-residue production
7 Paneer	Losses in loading & heating in the from of spillage and sticking.Discarding of whey serum During pressing & cooling Cutting & Packing of blocks /cubes (wastage and over filling)
8 Milk Powder production	Milk leakage in the pre-concentration, concentration stages.Milk loss in the form of burning in dryer chamber Milk sticking on the chamber surface Milk powder loss along with air from exhaust, pneumatic conveying duct line Milk powder losses as spillage during filling and bagging operationExcess filling during packing operation Storage- weight loss, spillage
9 Cultured products (Dahi/ Lassi etc.)	Spillage in loading and heating Spillage in culture dosing and incubation Packing & Storage losses
10 Ice creams & Ice-Candies	Mix preparation- spillage & improper Standardization Milk processing, Ageing & Flavouring vats spillage, and sticking losses Freezing and packing: spillage, over filling and less over run Hardening & Storage- Loss due to damage of packs.
11 Quality control	Incorrect testing, calibration for composition of milk and milk products.
12 CIP of storage tank, chiller pasteurizer and pipe lines	Improper recovery of sticking materials before draining of flush water.
13 Plant equipment maintenance	- Spoilage due to careless action - Break downs