Types of Cleaning Agents Used in the Dairy Industry

Every litre of milk that leaves a processing plant has passed through pipelines, tanks, heat exchangers, and filling machines – all of which must be spotlessly clean before the next production run begins. Milk residues, if left behind, quickly become breeding grounds for pathogens like Listeria, Salmonella, and E. coli. According to UC Davis’s dairy processing guidelines, all milk contact surfaces must be effectively cleaned and sanitized before each use. Achieving this requires not just water and effort, but a carefully chosen set of cleaning agents – each targeting a specific type of soil or contamination challenge.

Why no single cleaner is enough 🔗

Milk leaves behind a complex mixture of fats, proteins, sugars, and minerals on equipment surfaces. Fats and proteins are organic deposits that respond well to alkaline conditions, while minerals – particularly calcium and magnesium salts from both milk and hard water – require acid treatment to dissolve. The Tetra Pak Dairy Processing Handbook confirms that while most residues can be removed using pure alkali or acid solutions, formulated detergents with multiple additive types are widely used to improve overall cleaning efficiency. That’s why dairy plants typically deploy a range of cleaning agents, each with a specific function.

Alkaline cleaners 🔗

Alkaline cleaners are the primary workhorse in any dairy cleaning programme. They work by breaking down fat through saponification – converting fatty residues into soap-like substances that rinse away – and by dissolving protein films from heated surfaces. UC Davis DRINC describes alkaline compounds as the “guts” of dairy cleaners. The most commonly used include:

Caustic soda (sodium hydroxide, NaOH) 🔗

Caustic soda is the most widely used alkaline cleaner in dairy processing. It dissolves milk proteins, saponifies fats, and has inherent germicidal properties that provide a basic level of microbial reduction during cleaning. However, it lacks strong emulsifying power on its own and is highly corrosive to skin and some metals, so it is almost always used in blended formulations. Dairy Technology notes that caustic soda is typically combined with other alkalis to provide a balanced cleaning action.

Trisodium phosphate (TSP, Na₃PO₄) 🔗

Trisodium phosphate offers moderate alkalinity with notably high deflocculating and emulsifying power. It is effective at removing protein deposits and suspending soil particles, making it useful where a less aggressive but thorough cleaning approach is needed. Its use is restricted to concentrations of 0.5-1.5% in most applications due to environmental regulations limiting phosphate levels in wastewater.

Sodium metasilicate (Na₂SiO₃) 🔗

Sodium metasilicate provides strong alkalinity while being relatively less corrosive to metals compared to caustic soda. It has excellent deflocculating and emulsifying properties and is particularly valued for its ability to hold loosened soil in suspension during the wash cycle, preventing redeposition. It is often added to blended formulations to protect equipment surfaces from the corrosive effects of other alkalis.

Soda ash (sodium carbonate, Na₂CO₃) 🔗

Soda ash is the most economical of the basic alkalis and is valued for its good buffering capacity, which keeps the cleaning solution at a stable pH over extended periods. However, it is a poor water softener and performs poorly in hard water unless paired with sequestering agents to prevent calcium carbonate precipitation and the formation of milkstone deposits.

Acid cleaners 🔗

Once alkaline cleaning removes organic residues, mineral deposits – often called milkstone – remain. These are calcium and magnesium phosphate deposits that precipitate from milk or hard water, particularly on heated surfaces. Dairy Technology notes that acid cleaners must reach a pH of 2.5 or below at the point of use to be effective. Equipment like plate heat exchangers and tubular heaters are typically cleaned in two phases: first with alkali, then with acid.

Nitric acid (HNO₃) 🔗

Nitric acid is the most widely used inorganic acid in dairy CIP systems. It is particularly effective at removing milkstone and hard water scale from stainless steel surfaces. According to the Tetra Pak Dairy Processing Handbook, nitric acid is the most common acid used for cleaning dairy processing equipment. It is used at concentrations around 60% in automated CIP systems, though it is hazardous on skin and attacks tin readily.

Phosphoric acid (H₃PO₄) 🔗

Phosphoric acid is a moderately strong acid that serves as a safer alternative to nitric acid in many dairy cleaning applications. Beyond dissolving mineral deposits, it offers mild corrosion inhibition on stainless steel surfaces, making it valuable where equipment preservation is a priority. It is often found in formulated acid cleaners as part of blended solutions that also contain surfactants.

Organic acids 🔗

Organic acids such as citric acid, lactic acid, and acetic acid are milder options that prevent and remove calcium and magnesium salt deposits. They are less corrosive, safe on skin at use-dilutions, and can be easily combined with wetting agents for better surface penetration. They are commonly used in manual cleaning operations and for equipment made from materials sensitive to strong mineral acids.

Wetting agents (surfactants) 🔗

Water alone does not effectively wet metal surfaces, especially when they carry fat or oil residues. Wetting agents, also called surfactants, solve this by lowering the surface tension of the cleaning solution, allowing it to spread evenly across surfaces and penetrate into tight crevices, capillary pores, and spaces between the equipment surface and soil particles. The Dairy Site explains that alkaline cleaners routinely contain wetting agents alongside phosphates and chelating agents to maximise their ability to loosen and suspend soil.

Surfactants are organic molecules with a hydrophilic (water-attracting) end and a hydrophobic (fat-attracting) end, which allows them to simultaneously bind to both water and grease. They come in three main types: anionic, cationic, and non-ionic. In CIP systems, low-foaming surfactants or antifoaming agents are specifically required because excessive foam hinders the mechanical flow of cleaning solutions and makes thorough rinsing more difficult. Quimidroga’s CIP cleaning guide notes that antifoaming surfactants are standard additions to CIP detergent formulations for precisely this reason.

Sequestering agents (chelating agents) 🔗

Water hardness is one of the most persistent challenges in dairy plant cleaning. Hard water is rich in calcium and magnesium ions that react with cleaning agents to form insoluble precipitates – effectively deactivating the detergent before it even reaches the soil. Sequestering agents prevent this by binding to these metal ions and keeping them in solution, unable to form scale or interfere with cleaning chemistry.

The Dairy Processing Handbook lists sequestering agents (also called chelating agents) as standard additives in formulated dairy detergents, with EDTA (ethylenediaminetetraacetic acid) and phosphonates among the most widely used. LKL Services explains that sequestration agents tie up dissolved solids and carry them away in the wash solution, and that higher levels improve the effectiveness of active alkalinity, thereby aiding the overall breakdown of fats and proteins. Environmental regulations in many countries now limit phosphate use in cleaning formulations, pushing the industry toward alternative chelating agents such as GLDA and sodium gluconate.

Enzyme cleaners 🔗

Enzyme-based cleaners represent an increasingly important category in modern dairy hygiene. Rather than relying on chemical aggression, they use biological specificity – particular enzymes target particular types of soil. Proteases break down heat-denatured proteins that resist conventional alkaline cleaning, lipases assist in fat removal, and amylases address carbohydrate residues. Dairy Technology notes that proteolytic enzymes are particularly useful in cleaning membrane processing plants, where protein fouling is a major challenge.

A 2023 review published in Comprehensive Reviews in Food Science and Food Safety (Wiley) highlights additional advantages of enzyme-based CIP: reduced water usage, lower operating temperatures, shorter cleaning times, and significantly lower wastewater treatment costs. Enzymes also target biofilm matrices – the protective structures that harbour persistent bacterial colonies on equipment surfaces – making them valuable where chemical-only protocols fall short.

Chlorine compounds and sanitizers 🔗

Cleaning removes physical and chemical soil; sanitization eliminates microbial contamination. Chlorine is the most widely used chemical sanitizer in dairy plants. NDVSU’s dairy processing materials confirm that sodium hypochlorite is the most common form, functioning as the active antimicrobial agent. Chlorine works by oxidizing cellular components of bacteria and other microorganisms, destroying their ability to survive. Effective use requires maintaining concentrations of 100-200 ppm and adequate contact time.

It is critical to note that chlorine sanitizers are not a substitute for cleaning – they lose effectiveness rapidly in the presence of organic residues. This is why thorough mechanical and chemical cleaning must always precede sanitization. Additionally, chlorine can attack rubber gaskets and some plastics, and it should never be mixed with acid-based detergents, as this produces toxic chlorine gas.

Corrosion inhibitors 🔗

Corrosion inhibitors are added to cleaning formulations – particularly strongly alkaline or acidic ones – to protect metal equipment surfaces from chemical damage. These compounds form thin protective layers on metal, preventing pitting or etching caused by repeated exposure to aggressive cleaning chemicals. Sodium metasilicate, for example, is commonly included in alkaline blends partly because of its ability to buffer the corrosive effect of caustic soda on stainless steel and tin surfaces.

How these agents work together in practice 🔗

Modern dairy facilities use a systematic approach known as Clean-in-Place (CIP), where cleaning solutions circulate through equipment without disassembly. A standard CIP cycle typically begins with a water pre-rinse to flush loose residues, followed by an alkaline wash (caustic soda or blended alkaline detergent) to remove fats and proteins, an intermediate water rinse, an acid wash (nitric or phosphoric acid) to dissolve mineral deposits, a final rinse, and a sanitization step with a chlorine-based or peracetic acid solution.

The specific combination of agents depends on water quality, the types of products processed, equipment materials, and regulatory requirements. In hard water areas, for instance, sequestering agents become critical to every wash stage, not just acid cleaning. In cheese plants, proteolytic enzymes may be added to tackle the particularly stubborn protein residues typical of that environment. As noted in CIP cleaning research, the goal of every cleaning cycle is to remove substrates that allow microbial growth and to prepare surfaces for effective sanitization – and each category of cleaning agent plays a distinct, non-replaceable role in achieving that goal.

What do you think? Given that milk fouling on heated surfaces involves a mix of proteins, fats, and minerals, how would you prioritise the sequence and choice of cleaning agents for a pasteurizer compared to a cold storage tank? And with growing interest in enzyme-based cleaners, do you think they could eventually replace conventional acid and alkaline cleaning in mainstream dairy CIP systems?

References

1. https://drinc.ucdavis.edu/dairy-processing/cleaning-and-sanitizing-containers-and-equipment
2. https://dairyprocessinghandbook.tetrapak.com/chapter/cleaning-dairy-equipment
3. http://dairy-technology.blogspot.com/2014/01/cleaning-agents.html
4. https://www.thedairysite.com/articles/686/cleaning-and-sanitizing-milking-equipment
5. https://www.quimidroga.com/en/2022/03/17/cip-cleaning-in-the-food-industry/
6. https://www.lklservices.co.uk/health-safety/coshh-overview-for-dairy-chemicals
7. https://ift.onlinelibrary.wiley.com/doi/10.1111/1541-4337.13206
8. https://www.ndvsu.org/images/StudyMaterials/LPT/cleaning_and_sanitation_of_milk_plant.pdf