Dairy & food hygiene
Dairy CIP explained: why the order of alkali, acid and sanitiser matters
How clean-in-place works in a dairy, what milkstone is, and why formulated chemistry cleans faster than plain caustic and acid. With references to the Tetra Pak Dairy Processing Handbook.
Ask any dairy supervisor what holds up a shift and cleaning comes up fast. Every changeover waits on a clean that passes. Clean-in-place (CIP) exists so tanks, pipes and heat exchangers can be cleaned without taking them apart. But CIP only works if the chemistry, temperature, time and order are right.
What is actually stuck to the steel?
Milk leaves two kinds of soil. The first is organic: fat and protein. The second is mineral. When milk is heated above roughly 60°C, a hard deposit called milkstone builds up on hot surfaces. The Tetra Pak Dairy Processing Handbook describes it as calcium and magnesium phosphates, proteins and fat, which bind tightly and darken from white to brown over a long run [1].
No single chemical removes both soils well. Alkali breaks down fat and protein. Acid dissolves the mineral part. That is why the order matters.
A typical CIP sequence
For heated surfaces such as pasteurisers, the handbook outlines a programme like this [1]:
- Warm water rinse to push out residual product.
- Alkaline detergent circulation, typically 0.5 to 2% at about 75°C.
- Warm water rinse.
- Acid circulation, typically 0.5 to 1.5% at about 70°C.
- Cold water rinse.
Cold surfaces such as pipes and tanks usually need a shorter alkaline step and a final disinfection. Many plants now use a cold, no-rinse peracetic acid sanitiser for that last step, which also helps sites without reliable hot water.
Why formulated chemistry, not just soda and acid?
Plain caustic soda and commodity acid do clean. The trouble is how they behave on the surface. The handbook notes that surfactants lower surface tension so the detergent wets the equipment and the dirt more effectively, and that sequestering agents stop minerals from flocking together and redepositing [1].
In practice, that shows up as fewer re-cleans, fewer rinse cycles and less water sent to the effluent plant. It is the reason our INNOVA dairy range is built as formulated products rather than raw commodities. INNOVA CIP 50 is a formulated alkaline cleaner, INNOVA CIP Descale handles mineral scale and INNOVA PAA15 is a cold no-rinse sanitiser. On tanker CIP, customers can cut CIP time by up to 30 to 40%.
Three checks for your own CIP
- Is the acid step happening often enough? If you only descale when scale is visible, milkstone is already costing you heat transfer.
- Is the concentration measured, not guessed? Log it every cycle. Auditors will ask.
- Are you verifying the clean? ATP or swab tests on critical points tell you what the eye cannot.
If you want a quick read on where your programme stands, our free plant hygiene check takes about four minutes.
Quick answers
What is milkstone?
Milkstone is a hard deposit that forms when milk is heated above about 60°C. It is made of calcium and magnesium phosphates, proteins and fat, and it sticks tightly to heated surfaces such as pasteuriser plates.
Why do dairies use both alkaline and acid cleaners?
Alkaline cleaners remove fat and protein. Acid cleaners dissolve the mineral part of milkstone and scale. Running them in the right order cleans both kinds of soil.