Equipment History and Function

Cream Separator

The cream separator is a dairy machine used to separate fresh whole milk into cream and skim milk. Formerly the separation was made by gravity method, allowing the cream to rise to the top of a pan and then skimming it off. Laval of Sweden devised the first mechanical cream separator in 1880, based on the principle of centrifugal force.

How it Works
Whole milk is conducted into a bowl, commonly through a central tubular shaft. A spindle rotates the bowl at a rate of from 6,000 to 9,000 rpm, and a series of identical conical disks separates the milk into vertical layers. The heavier skim milk collects on the outer circumference of the rapidly whirling bowl, and the lighter cream tends to remain in the center. The pressure of the incoming whole-milk supply then forces the cream and skim milk out of the machine and into separate collecting vessels. The cream separator makes it possible to control the amount of fat (Called Butterfat) remaining in the milk. The gravity method ordinarily leaves one fourth of the fat in the milk, while the cream separator leaves only 0.01% to 0.02% of the fat in the skim milk. Since the latter process is much faster than the gravity method, there is less chance for harmful bacterial action.


In 1899 Auguste Gaulin obtained a patent on his homogenizer. The patent consisted of a 3 piston pump in which product was forced through one or more hair like tubes under pressure. It was discovered that the size of the fat globules produced were 500 to 600 times smaller than the tubes There have been over 100 patents since, all designed to produce smaller average particle size with expenditure of as little energy as possible. The homogenizer consists of a 3 cylinder positive piston pump (operates similar to a car engine) and homogenizing valve. The Pump is turned by an electric motor through connecting rods and crankshaft.

How it Works
If raw milk were left to stand, the fat would rise and form a cream layer. Homogenation is a mechanical treatment to the fat globules in milk brought about by passing milk under high pressure through a tiny orifice. This results in a decrease in the average diameter and an increase in number and surface area. The net result is a much reduced tendency for creaming of fat globules. To understand the mechanism, consider a conventional homogenizing valve processing milk at 2500 psi. As it first enters the valve, liquid velocity is about 4 to 6 meters/second. It then moves into the gap between the valve and the valve seat and its velocity is increased to 120 meter/sec in about 0.2 milliseconds. The liquid then moves across the face of the valve seat and exits in about 50 microseconds. The whole process occurs between 2 pieces of stainless steel in a stainless steel valve assembly.


The process of pasteurization was created by Louis Pasteur. Pasteur’s aim was to destroy bacteria, molds, spores, etc. He discovered that the destruction of bacteria can be performed by exposing them to certain minimum temperature for certain minimum time and the higher the temperature the shorter the exposure time required.

How it Works
There are three forms of pasteurization..... Batch or Vat, HTSTand UHT pasteurization.

  1. Batch or Vat pasteurization was the first form of pasteurization used. It heats the product up to 145 F for 30 minutes.

  2. The second is HTST, high temperature, short time pasteurization. As stated in the name, it is a shorter process with higher temperatures. The required temperature is typically 161 F to pasteurize the milk. This is a continuous method and a "hold tube" is used to transport the milk after it has been heated. The "hold tube" is sized so that it takes 15 - 20 seconds for the product to travel all the way through it. Once the product reaches the end of the tube, if the temperature is at 161F, it is then considered pasteurized.

  3. The third is UHT, ultra-high temperature pasteurization. This method is used mostly for coffee creamers and boxed juices in the US. The product is brought to 250F (under pressure) for only a fraction of a second.
click for more events