How to Choose the Right Detergent for Dairy Processing

In dairy processing, hygiene is non-negotiable. Every pipe, tank, heat exchanger, and valve that milk passes through must be cleaned thoroughly after each production run. But effective cleaning doesn’t start with scrubbing – it starts with choosing the right detergent. Pick the wrong one, and you risk leaving behind residues that harbor bacteria, damage equipment, or compromise the quality and safety of the final product. The selection of an appropriate detergent is shaped by several interconnected factors: the type of soil present, the chemical composition of water, the nature of the processing steps involved, the design of the plant, and the required level of cleanliness. Understanding each of these factors is the foundation of an effective dairy sanitation program.

Understanding milk soil – what you’re actually cleaning 🔗

Before any detergent can be chosen, processors must understand the nature of dairy soil. Milk soil is not a single substance – it is a complex mixture of organic and inorganic components that adhere to equipment surfaces in different ways and require different chemical actions to remove.

Organic soils consist of fat, protein, and sugars, while mineral soils are made up of inorganic salts – primarily calcium, magnesium, and iron – derived from milk itself or from the water used in processing. Each of these components behaves differently on equipment surfaces:

• Proteins – When protein residues accumulate, they can leave a bluish or iridescent haze on surfaces. They are best removed using chlorinated alkaline cleaners. If temperatures are too high during pre-rinsing, proteins denature and bond more firmly to surfaces, making them significantly harder to clean.
• Fats – Milk fat does not fully melt until 40°C (104°F), and alkaline cleaners are required to break it down through saponification. If wash water is too cold, fat smears rather than lifts, creating a sticky layer that can anchor biofilms.
• Minerals (milkstone) – The term “milkstone” describes the deposit formed by precipitated minerals on equipment surfaces, combined with organic material. It presents as white or yellowish buildup and requires acid cleaners for effective removal.

When milk is heated above 60°C, milk fouling starts to form – a deposit consisting of calcium and magnesium phosphates, proteins, and fat. This is especially significant in heat exchangers and pasteurizers, where these deposits can become tightly bonded to surfaces. Identifying the type and condition of soil is the first and most critical step in detergent selection.

Water chemistry – a silent factor in cleaning performance 🔗

Water is the carrier for every cleaning solution, and its chemical composition directly influences how well a detergent performs. The correct detergent and proper usage ratio will depend on factors such as water hardness, iron content, water use, soil type, and soil load.

Water hardness 🔗

Hard water – water high in calcium and magnesium ions – is a significant obstacle to effective cleaning. Hard water scale sticks to stainless steel and glass surfaces, where it can harbor milk residues and bacteria, and prevent alkaline cleaners from cleaning effectively. A well-chosen detergent for hard water conditions must include water-softening agents or chelating compounds like EDTA to neutralize these minerals before they interfere with the cleaning process.

Iron and other water impurities 🔗

Iron in the water supply contributes to red-to-brown or black deposits on equipment surfaces. These iron deposits require strong acid cleaners for removal. Other water impurities, such as sulfates and chlorides, also affect cleaning chemistry and must be accounted for when formulating or selecting cleaning agents. Processors should always have their water tested and factor these results into their detergent selection process.

Matching detergent type to soil type 🔗

No single detergent can address all types of dairy soil. Effective cleaning programs rely on matching the right chemistry to the right contaminant.

Alkaline detergents 🔗

Alkaline cleaners typically contain basic alkalies, phosphates, wetting agents, and chelating agents. They dissolve milk fats, proteins, and carbohydrates and loosen and suspend other soil particles for mechanical removal. The most common alkaline cleaner in dairy facilities is sodium hydroxide (NaOH). An effective alkaline detergent delivers a pH of 10.5-11.5 and an active alkalinity of at least 200ppm in the wash solution. Chlorine is often added to alkaline formulations to improve protein removal and prevent film formation, though it is important to note that these are cleaning agents, not sanitizers.

Acid detergents 🔗

Acid cleaners serve a different but equally important role. Acid cleaners remove or prevent accumulated mineral deposits or milkstone buildup. The most commonly used acid in dairy CIP systems is nitric acid (HNO₃), though phosphoric and citric acids are also used. The dirt on heated surfaces is normally washed off with alkaline and acid detergents, in that order, with intermediate water flushing, while cold surfaces generally require only alkaline cleaning with occasional acid treatments.

Formulated detergents and enzyme-based cleaners 🔗

Formulated detergents include additives such as surfactants, chelating agents, enzymes (proteases, amylases, lipases), and antifoaming agents to improve cleaning efficiency. Enzyme-based detergents are particularly useful in specialist environments like cheese production, where protein structures differ from those in fluid milk processing. However, temperature control is critical when using enzymes – they operate within specific ranges and will denature if exposed to excessive heat.

How processing conditions affect detergent choice 🔗

The nature of the food processing steps carried out in a facility has a direct bearing on what soils accumulate and how difficult they are to remove. Soil adhesion increases with time, dryness, and heating – which means that processing lines operating at high temperatures or running for extended periods will generate harder, more stubborn deposits that require more aggressive detergent formulations or longer contact times.

Heat exchangers used in pasteurization are among the most challenging surfaces to clean because milk proteins and minerals bake onto the plates under heat. Heat exchangers encrusted with coagulated protein must be exposed to circulating alkaline detergent followed by acid solution for a total of 20-60 minutes, whereas a simple milk tank wall typically only needs about 10 minutes of alkaline treatment. This variation means detergent selection cannot be standardized across an entire plant – it must be tailored to each piece of equipment and its operating conditions.

Plant design and equipment materials 🔗

The layout of a dairy processing plant and the materials used in its construction also influence detergent choice. For effective CIP, all surfaces must be accessible to the detergent solution, and equipment must be grouped into cleaning circuits based on compatible soil types and surface materials.

Stainless steel is the dominant material in dairy equipment, but most plants also contain rubber gaskets, plastic components, and specialized coatings. Certain detergents are incompatible with these materials. Strong alkaline detergents at high concentrations can degrade rubber and some plastics over time, while acid detergents can corrode specific metals if used improperly. All chemicals used on food contact surfaces should be approved, and dairy processors should request confirmation from suppliers that each cleaning chemical is suitable for use in their specific plant.

The role of temperature and concentration 🔗

Detergent selection cannot be separated from the conditions under which the detergent is applied. Temperature and concentration are two of the most critical performance variables.

For detergents to be effective, they need the correct wash water temperature throughout the wash cycle. Water at the end of the cycle must be a minimum of 120°F (49°C). Too cold, and fat will not fully lift from surfaces. Too hot, and some chemicals lose efficacy or become more corrosive. The wash phase in CIP systems typically operates between 55°C and 66°C to ensure effective removal of remaining soil after the pre-rinse.

Chemical concentration must also be carefully controlled. Too low a concentration produces incomplete cleaning; too high wastes chemicals, increases costs, and may damage equipment or leave residues that affect product quality. Concentration sensors in CIP systems should be regularly tested and calibrated to ensure accurate dosing throughout the cleaning cycle.

Desired level of cleanliness and sanitation 🔗

The level of cleanliness required is another factor that shapes detergent selection. Dairy equipment must achieve not just physical cleanliness – the removal of visible soil – but also chemical and bacteriological cleanliness. It is important to note that equipment can be bacteriologically clean without necessarily being physically or chemically clean. This means cleaning and sanitation are distinct steps, each requiring appropriate chemical choices.

For products such as UHT milk, where sterile conditions are required, the level of cleaning must go even further, and the detergent program must be designed to eliminate all residues that could compromise the sterility of the final product. In these contexts, the sequence, timing, and chemistry of detergent application become even more precise.

Building a comprehensive detergent selection strategy 🔗

Effective detergent selection in dairy processing is not a one-time decision – it is an ongoing process that adapts to changes in soil loads, water quality, seasonal variation, and equipment condition. Several factors impact cleaning: time, temperature, chemicals and concentration, mechanical effect, water quality, soil type, type of surface, cleaning method, and people. To get it right consistently, processors are advised to work closely with their chemical suppliers, conduct regular water quality testing, and monitor cleaning outcomes through visual inspection, microbiological testing, and equipment performance data.

Staff training is equally essential. Even the most precisely selected detergent will underperform if applied at incorrect concentrations, temperatures, or contact times. A well-designed cleaning program documents each step, sets standard operating procedures, and reviews outcomes regularly.

What do you think? Given that milk soil composition changes depending on processing temperature and product type, how should a dairy facility approach detergent selection differently for high-heat operations like pasteurization versus cold storage lines? And as water quality varies significantly between regions, what systems should processors put in place to continuously monitor and adjust their detergent choices to maintain consistent hygiene standards?

References

1. https://www.thedairysite.com/articles/686/cleaning-and-sanitizing-milking-equipment
2. https://edis.ifas.ufl.edu/publication/AN392
3. https://dairydynamics.com/cleaning/
4. https://dairyprocessinghandbook.tetrapak.com/chapter/cleaning-dairy-equipment
5. https://agrochemusa.com/maximize-performance-efficiency-of-cip-routines/
6. https://www.lklservices.co.uk/health-safety/coshh-overview-for-dairy-chemicals
7. https://www.bccdc.ca/resource-gallery/Documents/Educational%20Materials/EH/FPS/Food/DairyProcessingCleaning.pdf
8. https://dairy-cattle.extension.org/cleaning-and-sanitizing-milking-equipment/