Dairy sanitation practice: Which acid is most commonly used for removal of “milk stone” (calcium and magnesium scale) from dairy equipment and pipelines during acidic CIP cleaning?

Introduction:
“Milk stone” is a mineral deposit consisting mostly of calcium and magnesium salts, often combined with protein residues, that forms on dairy equipment surfaces. Effective clean-in-place (CIP) regimes alternate alkaline and acid steps. The acid step must dissolve mineral scale rapidly without excessive corrosion or residue formation.

Given Data / Assumptions:

• The goal is to remove calcium/magnesium carbonate and phosphate deposits.
• Chemicals must be compatible with stainless steel and elastomers commonly used in dairies.
• Industry norms favor fast-acting, rinse-friendly acids.

Concept / Approach:
Nitric acid is widely used in dairy CIP as the primary acidic cleaner for descaling. It dissolves carbonate/phosphate scales efficiently and passivates stainless steel surfaces, reducing corrosion risk when used at prescribed concentrations and temperatures. While phosphoric acid is also used, nitric acid remains the benchmark in many dairy standards for consistent, rapid scale removal.

Step-by-Step Solution:
Identify the deposit (milk stone) as mineral scale.Select an acid that both dissolves scale and is equipment-compatible.Nitric acid best matches speed, effectiveness, and passivation benefits for stainless systems.

Verification / Alternative check:
Standard dairy CIP procedures typically specify an alkaline wash for protein/fat followed by a nitric acid rinse to remove mineral scale and re-passivate metal surfaces.

Why Other Options Are Wrong:

• Phosphoric acid: Useful in some plants but generally secondary to nitric for milk stone removal.
• Gluconic/tartaric/acetic acids: Weaker organic acids; slower and less common as primary descalers in dairy CIP.

Common Pitfalls:
Overusing strong acids without inhibitors or passivation control can damage gaskets or cause pitting; always follow validated CIP recipes.

Final Answer:
nitric acid