Validating cleaning performance in dairy processing equipment

Cleaning and sanitizing dairy processing equipment is a complex task influenced by the nature of dairy products, intricate equipment designs, strict regulatory standards (FSMA, PMO), and environmental conditions. Dairy residues — such as milk proteins, fats, and minerals — can form stubborn films on equipment surfaces, promoting bacterial growth and making removal difficult. Pathogens such as Listeria, Salmonella, and Cronobacter are especially resilient, often hiding in hard-to-reach areas and posing significant contamination risks.

Inadequate sanitation can lead to product recalls and outbreaks, especially when manual cleaning is required for dry systems or equipment with complex internal geometries like heat exchangers. Equipment designed with 3-A Sanitary Standards plays a critical role in cleaning success. Features such as smooth surfaces, round corners, sanitary welds, gasket-retaining grooves requirements, and maintaining correct slope for proper drainage help eliminate common sanitation challenges. Easy access to cleaning areas is essential — if equipment is hard to reach, it increases the risk of missed spots and contamination.

3-A design also supports faster cleaning cycles, quicker verification, and minimal disassembly, reducing labor hours and production downtime. These designs are compatible with standard verification tools, streamlining audits and regulatory inspections.

“Clean” is both a visual and microbiological concept. It refers to the removal of visible and invisible contaminants — including dust, debris and microorganisms — from surfaces and environments. In industries like food and pharmaceuticals, cleanliness is validated through rigorous protocols, often requiring three consecutive successful cleaning runs confirmed by visual, microbial and chemical testing. Figure 1 illustrates the critical validation steps: pre-rinse, cleaning, post-rinse, sanitizing, and verification sampling.

Sharif Uddin has more than 25 years’ experience working in dairy, foods, cosmetics, OTC, and consumer products manufacturing facilities. He is currently working as principal engineer of process cleaning for Rockline Industries Inc., a global manufacturer of wet wipes and coffee filters. He is an SME in hygienic design, cleaning, and cleaning validation. He earned accreditation as a Certified Conformance Evaluator (CCE) in hygienic design and cleaning from 3-A Sanitary Standards, Inc. Sharif was involved as a group leader in the ASTM E55.03 WK98596 committee to develop the standard guide The Science and Risk-Based Design of Clean in Place Clean Friendly Equipment for Pharmaceutical and Biopharmaceutical Applications (CbDby Design). He is a regular speaker at the Pharmaceutical Cleaning Validation Conferences in Europe and the US.

However, a visually clean surface doesn’t guarantee it's free from bacteria. Acceptable residual limits must be defined by the quality department. For example, a tank that appears clean should still be swabbed for microbial testing to confirm sanitation. In cases where visual inspection is impractical — such as pipelines — sanitation and rinse water samples analyzed through Heterotrophic Plate Count (HPC) or Total Organic Carbon (TOC) testing can verify cleaning effectiveness. There are several methods to verify cleanliness.

1. Visual Inspection – Visual inspection is defined as the process of using the eye, alone or in conjunction with various aids like a flashlight or borescope, from which judgments may be made about the condition of the equipment to be inspected. It is a primary method to verify cleanliness; however, operators need to be trained and qualified to perform this task.
2. Adenosine Triphosphate (ATP) – It is a popular method to measure the organic residue on the surface. It is a rapid method to check the cleanliness of the surface. It helps the operator to ensure the equipment surface is free of residue.
3. Sanitation Swabs – Surfaces are swabbed and cultured to detect bacteria or fungi. It is highly accurate, but it takes time (three to five days) to process. The QA department uses swabs to ensure the equipment is cleaned and sanitized effectively before running for production.
4. Heterotrophic Plate Count (HPC) – HPC is utilized to assess the bacterial load in rinse water. It helps determine whether the bacterial population in a 100 mL sample exceeds acceptable limits, which would indicate contamination. HPC testing is instrumental in evaluating whether a production line is contaminated. Typically, a pre-detergent sample is collected to identify existing contamination, while a post-sanitizer rinse sample is analyzed to verify the effectiveness of the cleaning process in eliminating bacterial residues.
5. Total Organic Carbon (TOC) – TOC analysis is used to detect any remaining organic residues in the rinse following cleaning with detergent and sanitizer. During cleaning validation, TOC serves as a key indicator to confirm the effective removal of cleaning agents and product residues. Prior to validation, an acceptable TOC threshold must be established to ensure compliance with cleanliness standards.

3-A equipment simplifies the validation steps. Its design allows for easier cleaning and verification, enabling faster line changeovers and production restarts. By eliminating problem areas and supporting standard verification tools, 3-A equipment reduces audit times and frees up QA and operations personnel.

Ultimately, “clean” is not a fixed endpoint but a balance of necessity, perception, and consequence. In everyday life, clean may mean comfort; in industry, it means precision and safety. The real challenge lies not in cleaning for appearance but in defining cleanliness in a way that aligns with quality standards, operational efficiency, and regulatory compliance. True cleanliness isn’t absolute sterility; its responsible adequacy achieved through three pillars: hygienically designed equipment, validated cleaning procedures, and reliable verification methods. When these elements align with 3-A Sanitary Standards, dairy processors gain confidence in every batch, every shift, and every audit.

3-A Design Features That Make Cleaning Verification Easier

• Self-draining designs eliminate pooling that harbors bacteria.
• Smooth, 32 Ra or better finishes prevent product adhesion.
• Accessible inspection ports enable visual verification without disassembly.
• Standardized connections facilitate consistent CIP flow rates.
• Minimal dead legs reduce microbial harborage points. DF