Cleaning milking systems - basic principles and practices

Proper cleaning of milking systems will ensure a high quality, salable product. Additionally, adherence to high standards of sanitation will boost consumer confidence in the safety of milk products.

Why Clean?

If you are dealing with a milking system that isn’t cleaning properly, you may find yourself wishing that the whole problem would just go away. Certainly, modern cleaning practices are producing a product that is far superior to the milk that our grandparents drank. So, why do we worry so much about cleaning our milking systems. For one thing - It’s the Law! The Pasteurized Milk Ordinance (PMO item 10r) requires that all milk contact surfaces be washed after each use. Additionally PMO item 11r states that milk contact surfaces must be sanitized prior to each use.

Properly cleaning milking systems is critical to produce quality products. Dirty milking systems allow bacteria to grow, leading to damage and contamination of milk. The result will be, at best, unpalatable products with limited shelf life. In worst case scenarios, human health will be endangered. Certainly, no one in the dairy industry would like to go through the equivalent of the Alar crisis in the apple industry or E. coli: H157 concerns in the food service and meat packing areas. Food safety is a major concern among consumers in many countries. Production cleanliness standards can improve consumer confidence in the quality and safety of milk and milk products.

From a purely selfish perspective, proper cleaning of the milking system will increase profitability. Low bacteria count milk generally leads to premium payments. A clean, sanitary system will help maintain those low bacteria counts.

The “Perfect” Cleaning & Sanitizing System

Dairy producers use a number of different cleaning products and systems. Systems and products certainly differ between countries, but may also differ regionally or within a country. Nevertheless, certain characteristics are required from any cleaning system. The perfect system for cleaning and sanitizing milking equipment would meet the following criteria:

  • Removes all soils from all surfaces
  •  Kills/removes bacteria
  • Non-corrosive to equipment
  • Minimizes time and energy required
  • Safe for humans: handling and food residues
  • Safe for environment

The Principles of Cleaning

The purpose of cleaning is to remove soil from the system, thereby limiting bacterial growth. Cleaning principles are relatively constant among systems. Both water and chemicals are involved in removing milk soil. The efficiency of the cleaning process will be impacted by the time involved in cleaning, cleaning temperatures, and system design and maintenance.

Milk soil is a composite of several milk components. The composition of milk soil is detailed below.

Water 87 20 3
Fat 4 25 3-18
Protein 3 20 4-44
Lactose 5 2 0
Minerals 1 10 42-67

Cleaning programs must effectively handle all of these components.This task is complicated by the fact that the various milk components have distinctly different solubility characteristics.

Milk fat is liquid above 105-110 degrees F. Milk fat will start to solidify at cooler temperatures. The solidified fat will then stick to surfaces.

Milk protein will denature at high temperatures. Denatured milk protein adheres tenaciously to surfaces. It may buildup in layers and become very difficult to remove.

Milk sugar or lactose is water-soluble and is easily removed with warm water.

Milk contains trace amounts of minerals that can leave deposits on surfaces. These minerals may combine with other materials such as proteins to form milkstone.


Water deserves special mention in the cleaning process. US dairy farms use large volumes of hot water, aggressive chemicals, and turbulent fluid flow to react with and remove the components in milk films. Because of environmental and worker safety concerns, these practices may change in the future.

Hot water has a number of functions during the cleaning process. Hot water acts as a solvent and diluent for milk sugar and cleaning chemicals. By driving slugs of cleaning solution through the system, water acts as a scouring agent on surfaces. Water is a heat transfer agent, allowing heat energy to accelerate chemical reactions throughout the system. And lastly, water is the carrier that suspends and carries soil components out of the system.

Water quality an important consideration during cleaning.

Dissolved minerals (calcium and magnesium salts) can interfere with chemicals used to remove soils. This is commonly known as the “water hardness effect”. Other mineral salts, such as barium sulfate and silica, may leave deposits on surfaces. Iron can leave rust-colored deposits.

Buffering capacity of water will have an impact on the action of alkaline detergents, acids and sanitizers. Any dissolved organic material in the water supply may also interfere with cleaning compounds.


Proper cleaning of milking systems will ensure a high quality, salable product. Additionally, adherence to high standards of sanitation will boost consumer confidence in the safety of milk products.

The cleaning process centers on the removal of milk soil from the milking system. Because of the varied nature of the different milk soil components, this can be a complicated process. A number of different cleaning procedures are in use around the world; however, the ideal system for any producer has certain common characteristics. These are; removal of all soils from all surfaces, removal or destruction of bacteria, non-corrosive to equipment, minimizes time and energy requirements, is safe for humans to handle, leaves no harmful food residues, and is safe for equipment.

Cleaning efficacy will be affected by the type(s) and concentration(s) of chemicals used, as well as the duration and temperature of the cleaning process. System design and maintenance, especially with regards to slug formation and drainage, can play a major part in the cleaning process. These factors will be discussed in subsequent articles.


Thomas C.  Hemling

Thomas C. Hemling
5 articles

VP Research & Development, DeLaval Inc.

Tom Hemling received his Organic Chemistry from the University of Cincinnati in 1985. Since 1991 he has been associated with DeLaval International, AB, most recently as Vice President of Global Technology, Business Unit Hygiene, Drongen, Belgium.

Tom has published and or presented over 35 papers world wide on the subject of Teat Dips.

He is a member of the American Chemical Society, Union of Concerned Scientists, National Mastitis Council and the American Association of Bovine Practitioners.

Read more »



Every day millions of dairy animals are milked, fed and maintained by DeLaval solutions in more than 100 countries worldwide – and DeLaval meets with over 10 000 milk producers on their farms. 

Read more »