Key Concepts of Cleaning and Sanitizing

Proper cleaning and sanitizing is essential to producing high quality, safe dairy foods. A well-informed and trained staff provides the foundation for safe food processing.
Key Concepts of Cleaning and Sanitizing - Articles


Proper cleaning and sanitizing is essential to producing high quality, safe dairy products. A well-informed and trained staff provides the foundation for safe food processing.

The key concepts of sanitation controls are knowing what to clean, what soils are present, best practices for cleaning steps and washing factors, and understanding how to handle cleaning chemicals safely.

Cleaning versus Sanitizing

The first step in Sanitation Control is to understand the difference between cleaning and sanitizing.

  • Cleaning removes soils from surfaces
  • Sanitizing reduces the microorganisms on surfaces

An area must be cleaned before it can be sanitized. You can't sanitize dirt!

What to Clean

The first thing that comes to mind in cleaning is food contact surfaces. But cleaning the outside of equipment, the environment, and personnel hygiene are also necessary to maintain a sanitary environment for food processing. Personnel hygiene (hand washing, uniforms) should be addressed with the Good Manufacturing Practices (GMPs) for your facility, and will not be covered in this article.


These are examples of places to clean in a dairy and food processing plant:

  • Food contact surfaces
    • equipment surfaces
    • tables and preparation areas
    • conveyors
    • utensils
    • bins and totes
    • packaging materials
  • Outside of equipment
  • Environment
    • floors
    • drains
    • walls
    • light fixtures

The type of food contact surface is an important consideration when determining what types of cleaners and practices to use. The best materials for food processing are durable, non-porous, food grade, and easily cleanable. Materials that pit, rust or have rough surfaces have microscopic-size valleys that are highly desirable spaces for unwanted bacteria to grow and form hard-to-clean biofilms.

Typical materials found in food processing plants include stainless steel, plastic, and tile. Some dairy plants package milk in glass bottles. Some cheese makers use wood boards for aging and cleaning procedures should be in place to ensure the boards are sanitary.

Equipment design and plant layout should be considered from a cleanability perspective. You need to be able to reach around and under equipment to clean it properly.

Types of Soils in Dairy Plants

Milk contains 5 types of soils.


Milk carbohydrates are primarily lactose with minor amounts of other sugars. Sugars typically dissolve in water and can be removed with warm water.


Milk proteins consist of the caseins and serum (whey) proteins. They may or may not be soluble in water. Typically proteins are removed from surfaces using chlorinated alkaline cleaners (high pH); sometimes enzymes and oxidizers are added to help remove proteins. When protein residues build up they leave a bluish or rainbow haze on equipment surfaces.


Milk fat consists of many fatty acids arranged in triglyceride structures that give it a broad melting range. Milk fat is not fully melted until 104°F (40°C). Alkaline cleaners (high pH) are needed to saponify the fat and remove it from surfaces. It is critical that the wash water be at least 120°F at the end of the wash cycle to ensure that the milk fat is removed completely from all the surface and pipelines in the processing system. If the water is too cold, then the fat will smear rather than being removed. This can result in a layer of sticky fat inside the system that serves as an anchor point for bacteria to form biofilms.


Milk minerals consist of calcium, phosphorous, magnesium, with trace amounts of other minerals. Minerals are removed using acid cleaners (low pH). Milk stone is a whitish or yellowish build up of mineral residue on surfaces. Water conditioning may be used to help prevent regular deposition of water and milk minerals on processing and environmental surfaces.


Microorganisms in a dairy plant can originate in milk, water, air, be tracked in on boxes, pallets, shoes, personnel, and other vectors. Microorganisms can be washed away from surfaces during routine cleaning, but since they are always present in the environment, food contact surfaces should be sanitized prior to use. The main reason to sanitize equipment is reduce the microbial load on surfaces prior to use.

Biofilms form when bacteria get lodged in crevices and can not be washed away. The bacteria attach to the surfaces, multiply and form large masses that become encased in soils which protect them from cleaning and sanitizing chemicals. These communities contaminate product that moves across the equipment surfaces, and pieces can break off during processing, causing sporadic high micro counts in products.

How to Clean

The specific steps used to clean and sanitize equipment and environmental areas are unique to each processor. Sanitation Standard Operating Procedures (SSOPs) are written, step-by-step instructions on cleaning equipment, processing lines, environmental areas, and master sanitation schedules. See the article on Sanitation Standard Operating Procedures for guidelines and tips for writing SSOPs.

Equipment and environmental areas may cleaned using clean-in-place (CIP) systems, clean-out-of-place wash tanks (COP), and manual techniques. When using COP tanks, make sure all parts are completely submerged to ensure adequate cleaning. Hoses and pipes that stick out of the tank will not get washed thoroughly. Follow manufacturers instructions and chemical suppliers suggestions when using CIP and COP systems. A good reference for dairy equipment cleaning procedures is Guideline 29 Cleaning and Sanitizing in Fluid Milk Processing Plants, published by The Dairy Practices Council.

Many dairy plants use a color-coded brush system to prevent contamination from raw to pasteurized products, and from non-food contact and environmental surfaces to food contact surfaces. It is highly recommended that a separate (black) brush be used ONLY for cleaning drains. Long plastic handles with "drains only" printed on them can be purchased from brush suppliers.

When using buckets for sanitizing, make sure the buckets are thoroughly clean before mixing the sanitizer. If the sanitizer appears cloudy, it is no longer effective and should be replaced.

Cleaning Chemical Selection

The selection of cleaning and sanitizing chemicals for use in your facility will depend on:

  • soil type
  • surface type
  • application method (clean-in-place, clean-out-of-place, manual
  • environment
  • water quality

Often different areas or environments in the plant will require different types of cleaners. For example, a clean-in-place system will use cleaners that don't foam as much as manual cleaners. The sanitizer used in footbaths may be different than the one used of food contact surfaces.

There are many types of cleaning and sanitizing chemicals available. Be sure to follow the directions for that particular cleaner or sanitizer - they all have their own optimal concentrations. Be aware of the use requirements and limitations of your sanitizer - many sanitizers are "no-rinse" and should not be rinsed between application and food processing. Sanitizers usually have a period of effectiveness that only lasts for several hours, so if you sanitize your equipment after cleaning the night before, you may need to sanitize again just prior to processing.

The best approach is to assess your facility, have your water tested, and work directly with then a chemical supplier to set up a cleaning and sanitizing system that fits the needs of your facility and company philosophy.

Cleaning Steps and Washing Factors

The key concepts of cleaning and sanitizing are summarized in 4 steps:


  • removes loose soil from surfaces prior to cleaning
  • use warm water (100-120°F)


  • removes carbohydrate, fat, protein and mineral soils
  • follow SSOPs for cleaning procedures and chemical selection
Washing Factors (TACT)
  • Time
    • too little: not enough surface interaction
    • too much: temperature cools, detergent deposits
    • just right: surface wets, soils are removed and washed away
  • Action (Mechanical Force)
    • loosens soils and disrupts biofilms
    • need to have contact with all surfaces
    • use turbulent flow, slugging
  • Chemical Concentration
    • too little: not enough cleaning power
    • too much: may reduce efficiency, may leave residues, wastes money
    • just right: does the job
  • Temperature
    • use the correct temperature according to the SSOPs
    • water should be 120°F at the end of the wash cycle
    • too hot: proteins denature and deposit, dangerous for personnel


  • removes detergent and chlorine
  • rinse water may be acidified (Acid Rinse)
  • removes minerals and prevents mineral deposits


  • reduces the number of microorganisms on surfaces
  • sanitizes surfaces before use
  • only clean surfaces can be sanitized!

Chemical Safety

Chemicals are used in dairy processing plants and QA laboratories. OSHA regulations state that it is the employer's responsibility to provide adequate training and access to information to ensure that employees work in a safe environment and minimize accidents.

Use demonstrations freely when conducting chemical safety training to educate employees how to properly mix chemical solutions, label chemical containers, wear the correct personal protective equipment (PPE) for the task at hand, and clean up spills. Make sure to document the training session (date of the session, topics covered, employees present) and place it in the training section of your Food Safety Plan.

People that work with cleaning and laboratory chemicals should know:

Correct chemical use

  • the right chemical and concentration needed for the job
  • the correct mixing and use procedures
  • how to label and store chemicals properly

Chemical properties

  • the physical state (solid, liquid, gas), concentration, and pH of the chemicals
  • physical hazards (flammable, explosive, reactive)
  • heath hazards (burns, poisons, carcinogens)

Personal Protective Equipment (PPE)

  • gloves, lab coats, coveralls and footwear
  • eye, face, and head protection required
  • use the correct materials for the task


  • use chemical rated gloves, not latex gloves for handling cleaning chemicals
  • wear a full face mask when handling caustic and acidic cleaning chemicals

Accident and Spill Response

  • the use and location of emergency equipment
  • emergency first aid procedures
  • have emergency contact numbers easily accessible
  • have spill kits accessible and use procedures in place

The Details

The Details summarize the best practices for effective cleaning and sanitizing in dairy and food plants.

Follow SSOPs

  • develop Standard Sanitation Operating Procedures (SSOPs) specifically for equipment and environmental areas to meet the needs of your facility
  • include step-by-step directions on how to clean, and how often to clean
  • specify the correct chemicals, times, temperatures and processes to use

Use the Right Supplies

  • correct chemicals and concentrations
  • appropriate Personal Protection Equipment (PPE) for chemical handling
  • color-coded brushes and buckets, the correct wash tanks, etc.

Fill Out Records

  • sanitation records and logs
  • Food Safety Plan monitoring and verification records
  • if it wasn't documented, it wasn't done!

Take Pride

  • smile and take pride in producing clean, safe food!

Printing the Article

This article is formatted for printing as a summary poster and as flashcards with the key concepts on the front and full details on the back.

The poster and flashcards are visual reminders of key concepts in cleaning and sanitizing dairy and food processing plants. They can be displayed on doors, lockers, processing areas, CIP rooms, chemical storage areas, lunch rooms, and employee notice boards. The flashcards can be posted with the key concept side visual as a quick reminder or posted with the details visible for more information. The flashcards can be used a quiz aids for on-site training.

The poster and flashcards are available as a free download or can be purchased on water resistant paper suitable for display in a dairy plant environment.