INTRODUCTION

Milk Processing

The most important section of any dairy is the Milk Processing section. The milk that is collected from different societies and milk unions is brought to the dairy in chilled conditions sealed in milk tankers.Milk processing is required to eliminate the dirt and harmful pathogens from milk, and also make the milk a homogeneous liquid containing all the important ingredients like fat, SNF(Solid Not Fat) etc in right proportions as may be required.

The three basic steps of milk processing are:

1. Clarification
2. Homogenization
3. Pasteurization

FLOWCHART

Flow Diagram of Milk Processing

Mother Dairy Calcutta

Process

The process is as follows. 1st the milk enters into the 1st regeneration in chilled condition. It is here that the heating starts by absorbing heat from the outgoing hot milk. The heat absorption takes place in plate heat exchangers. The milk is heated to a temperature of 20oC. It then passes through the clarifier. After clarification, it returns and enters into the 2nd generation where the milk is heated to a temperature of 55-60oC. Then this milk passes to the homogenizer. The homogenized milk returns back and is heated finally to 80oC. The temperature of the milk is held at 80oC for 15 seconds. Then this milk passes through the two regeneration steps again losing heat to the incoming milk in PHE(plate heat exchanger) and is finally chilled to 4oC by the chilled water from the refrigeration section.

Clarifier

The clarifier is used to clarify the milk. Remove all the soluble dirt from the milk. It works on the principle of centrifugal force. A motor rotates the clarifier at a high speed so that all the dirt having high specific gravity are forced to the inner wall of the clarifier from where it is removed from time to time. The waste is termed as sludge.

Homogenizer

Homogenizer is a highly sophisticated machine. Its main function is to homogenize the milk. Usually the fat molecules in milk being lighter tend to float on the milk without mixing into it proportionally. The homogenizer performs the function of breaking the fat molecules to a size of less than 2 micron. It is done with the help of two micron valves in the homogenizer. The milk along with its fat molecules is forced through this valve at a very high pressure of 130bars. This breaks the milk and fat molecules to atomic dimensions and mixes them together giving homogenized milk. It uses a huge 250 HP squirrel cage Induction Motor.

Pasteurizer

The pasteurizer is perhaps the most important machine in a Dairy Industry. Mother Dairy has three pasteurizers. Pasteurization is done to kill germs that may be present in the milk and are potentially harmful to our health. The Pasteurization process involves heating the milk to a temperature of 71.8oC and then holding it at that temperature for 15 seconds followed by chilling it back to 4oC. This process kills most of the harmful pathogens. The heating is done with the help of regeneration process and by hot water produced by steam from the BOILER. Chilling of the milk is done by ice cold water from the refrigeration units.