What is cleaning?

The purpose of cleaning the milking equipment is to achieve microbial control. Cleaning includes both the removal of any unwanted material left after milking and the killing of micro organisms, usually called disinfection. Cleaning should always be performed as soon as possible after each milking.

The cleaning of stationary plants is performed with the help of water. Usually, this is done by clean-in-place (CIP) methods, that is, the equipment is not dismantled for the cleaning. This is the common way of cleaning pipelines and other parts of closed plant equipment in the food industry. The milking plant at the farm is also cleaned with CIP-systems, although there are some differences in how to create and regulate the water flow. This and the other methods for reaching the desired cleanliness will be described in the following pages.

When is the milking plant clean?

The definitions of cleaning are as follows:

 - Clean equipment is free from visible impurities.

 - Microbiologically clean refers to equipment that harbours so few micro organisms that the quantity and quality of a possible contamination of milk is of no practical importance to the quality of milk in relation to health or product quality.

 - Chemically clean equipment contains so little foreign matter that  chemical contamination of the milk is below the relevant standard.

Generally, milk contact surfaces will look and feel clean when properly cleaned. The amount of microorganisms, usually bacteria, will hopefully then be so limited that the demand for microbiological cleanliness is met.

Which contaminants have to be removed?

After milking the milking equipment is soiled with residues of liquid milk and air dried films of milk. The main part of this old milk (often called soil) is easily removed by rinsing with water. However, the last part is often harder to get rid of. Therefore, the most difficult task of the cleaning system is to remove this last soil.

The milk residues consist of, among other things, fats and proteins, which are delicate substrate and protection for bacteria. Of course, the milk also contains bacteria, which will multiply at a high rate if not removed. For the battle against bacteria, the removal of the milk residues is a good start, since these residues are the main  locations for bacteria.

Although most of the residues are removed, bacteria can still attach to visibly clean surfaces. Under favourable conditions they can also form a biofilm, which can be very hard to remove. Therefore, it is of utmost importance to prevent the formation of this biofilm.

Another contamination, that originates from both milk and hard water, is milkstone, a layer of scale mainly formed by cations like calcium and magnesium. Besides giving the equipment an unclean appearance, milkstone could harbour and protect micro organisms.

Back to top

Which parts of the milking plant have to be cleaned?

Basically, all parts of the milking machine which come in contact with milk have to be cleaned.

These parts could be divided into three groups:

- The first group consists of parts which hold milk as well as vacuum during milking. These are the milking units, milkmeters, the milk line and the receiver.

- The second group consists of the delivery line between the receiver and the milk cooling tank including the milk pump and sometimes also a plate cooler. It is common for the milk to be transported without the help of vacuum, in the delivery line.

- Finally, the third area is the milk cooling tank. The reason for dividing the milking plant into these groups is that they are cleaned in different ways.

Parts of the milking plant which have to be cleaned.

Not only the inside parts of the milking machine have to be cleaned. Also the environment around the plant, mainly the milk room and the milking parlour, as well as some outside parts of the milking machine, e.g. clusters, should be cleaned.

What factors are involved in cleaning?

Cleaning is basically the process that removes soil from the equipment which is to be cleaned. In order to make this process as efficient as possible, four important factors are combined.

These are:

- mechanical force,

- cleaning agents,

- heat,

- contact time.

Water is of course the key to get these factors to work towards a satisfying cleaning result.

Factors involved in cleaning.

Mechanical force

Soil that has firmly adhered to surfaces in the milking plant, needs to be exposed to a mechanical force in order to be loosened. This force is usually exerted by circulating water in the plant, but could also take place through scrubbing or spraying. Both the milking plant and the cooling tank can be cleaned with one or both of these methods.

Cleaning agents
Cleaning agents could be divided into detergents and disinfectants. Often, however, the cleaning agents consist of both. Detergents assist in removing the soil by helping to loosen it and to hold it in suspension so that it can be removed during rinsing. Another important task for detergents is to prevent cations like calcium and magnesium forming milkstone.

Detergents can be either alkaline or acid. Often a alkaline detergent is used as the main detergent. Acid detergents are then used, e.g. once a week, in order to remove milkstone.

Disinfectents are used to kill microbes. Often disinfectants consist of chlorine or chlorine compounds. In some alternative cleaning systems disinfectants are replaced by the use of heat.

Heat
The role of heat is to improve the ability of dissolving and  emulsifying different materials. Detergents are more easily dissolved when the water is warm. It is also important that warm water is used in the removal of fatty materials.

Contact time
Contact time means that the water, heat and cleaning agents must have sufficient time to perform the cleaning. The time needed varies depending on cleaning method.

Water
As mentioned before water is important for the cleaning result for several reasons. It carries cleaning agents and heat, and exerts mechanical action on the surfaces to be cleaned. The transportation of soil is another important task for water, since the soil is the main hiding-place of microorganisms. With the help of cleaning agents, heat and turbulent water, the soil is suspended or dissolved, which makes it easy to remove. This removal is an important step towards the successful cleaning of the milking plant.

At the same time as being a key tool in the cleaning process, water can contain a wide variety of impurities which could jeopardize the cleaning result. Important types of elements, which may be regarded as impurities, are calcium, magnesium and other ions which make the water hard.

Back to top