Added Water in Milk When inspectors from Government Services collect that milk sample a number of tests are performed at the Food Quality Laboratory in the Animal Health Division. One of these is the freezing point. The purpose is to determine whether or not water may have been added, regardless of the reason, be it intentionally or accidentally. When water is added to milk the concentration of salts and lactose dissolved in the milk is diluted. Dilution of milk with water progressively gives a freezing point approaching that of pure water.

Water is present if the freezing point of the serum (milk) is -0.512oC or closer to 0oC. If you were reading a scale it would look like the following example:

0 degrees Celsius = 100% added water

-0.257 = 50% added water

-0.387 = 25% added water

-0.491 = 5% added water

-0.502 = 3% added water

-0.507 = 2% added water

-0.512 = 1% added water

-0.517 = 0% added water

-0.52 = No added water

-0.525 = No added water

As you can see, as the temperature moves up from -0.525 towards -0.512 the milk becomes more diluted with water and can freeze more quickly.

Factors that affect the freezing point may include the season of the year; age, health and breed of the cow; access to water; feed; weather; ambient temperature; time of milking; fermentation; vacuum treatment of milk; and the freezing and holding of samples before the freezing point is determined. Also the addition of milk solids will markedly lower the freezing point.

The most common ways water is added to milk is either through carelessness or it was done deliberately. Often water is added to milk when poorly graded milk lines do not drain completely. In the short term these lines should be blown (admitting bursts of air though a milk valve at a distant part of the line) before milking. Sometimes water may collect in the bulk tank and someone forgets to check. Sometimes when washing the outside of the tank water inadvertently accesses the tank. Unfortunately, water could be added on purpose to increase the quantity for financial gain. However, as this is regularly checked, this gain could only be short term and the penalty, significant.

Did you realize that 300 feet of 2" milkline, if completely filled with water, would hold about 185 liters. For example, if you receive a report stating a freezing point of -0.502 C, doing the calculation using -0.517 C for normal milks freezing point, equate -0.517 - 0.502 = -0.015. (-0.015/-0.517) x 100 = 2.9% added water.

That translates this way. If you sampled 1000 liters of milk with a 2.9% added water test, then there was approximately 1000 x .029 = 29 liters added. If that was over four milkings it would mean 7.5 liters found its way into the tank each milking. Seven liters per milking is not difficult to hang up in a poorly graded milkline.

So if a report comes back with added water you should now know how the figure is calculated and the possible causes and remedies.

For additional help or information contact:

Tel: (709) 729-6826