Milk processing involves various mechanical operations such as collection, filtration, cooling, pasteurization, separation, homogenization, storage, and packaging. The equipment used for these operations must maintain hygiene, durability, thermal efficiency, and corrosion resistance due to the sensitive and perishable nature of milk. The materials used for fabrication of milk processing equipment play a vital role in ensuring these requirements are met.
Materials Used in Milk Processing Equipment
Milk and dairy products are highly susceptible to microbial contamination and spoilage, hence the materials used must ensure sanitary design and cleanability. The most common materials include:
1. Stainless Steel
- Grade 304 (18% Chromium, 8% Nickel):
- Most commonly used material in milk handling and processing equipment.
- Offers excellent corrosion resistance, especially against organic acids present in milk.
- Non-reactive with milk, does not affect taste or nutritional quality.
- Easy to clean and polish, making it ideal for CIP (Clean-In-Place) systems.
- Grade 316 (18% Chromium, 10% Nickel, 2% Molybdenum):
- Used where higher resistance to chlorides and acids is needed, especially in coastal or chemical-prone environments.
Applications:
Used in milk storage tanks, pasteurizers, pipelines, valves, separators, and homogenizers.
2. Mild Steel (Carbon Steel)
- Sometimes used for non-product contact areas like equipment frames or outer covers.
- Cheaper than stainless steel but prone to rust, hence not recommended for milk-contact surfaces.
- Requires painting or coating to prevent corrosion.
3. Aluminium
- Lightweight and has good thermal conductivity.
- Used in some portable equipment or small-scale vessels.
- Less corrosion-resistant than stainless steel; not preferred for long-term use or heavy-duty applications.
4. Plastics and Polymers
- Food-grade plastics like polyethylene, polypropylene, and PTFE (Teflon) are used for gaskets, valves, pipes, and flexible hoses.
- Resistant to chemicals, lightweight, and easy to mold.
- Must comply with food safety standards (such as FSSAI, BIS, or international codes like FDA or ISO).
5. Rubber
- Used in seals, gaskets, hoses, and suction pipes.
- Must be food-grade and resistant to cleaning agents.
- Natural or synthetic rubber like nitrile or EPDM is used for flexibility and tight sealing.
6. Glass and Borosilicate
- Used in laboratory equipment and sight glasses in processing lines.
- Transparent and chemically inert, allowing visual inspection of milk flow and cleanliness.
Importance of Proper Knowledge in Equipment Selection
Selecting the correct equipment for milk processing is not just about the material—it also involves understanding capacity requirements, production targets, energy efficiency, and maintenance needs. The following points highlight why proper knowledge is essential:
1. Appropriate Size and Capacity
- Equipment should match the volume of milk to be processed daily.
- Over-sized equipment leads to underutilization and increased operating costs.
- Under-sized equipment causes bottlenecks and loss in productivity.
Example:
If a dairy plant receives 10,000 litres of milk per day, a pasteurizer with a capacity of only 2,000 litres per hour would require 5 hours of continuous operation. If milk supply increases, higher capacity models or multiple units might be required.
2. Efficiency and Performance
- Understanding the working principle (e.g., centrifugal force in cream separators, plate heat exchangers in pasteurization) helps in choosing the right type.
- Equipment like homogenizers, chillers, and pasteurizers must perform consistently under varying loads.
- Properly selected equipment ensures optimum product quality with minimum wastage.
3. Hygiene and Food Safety
- Equipment must be easy to clean, sterilize and inspect.
- Knowledge about Clean-in-Place (CIP) systems and hygienic design standards helps in avoiding bacterial contamination.
- Poorly selected equipment may have hidden corners or joints that harbor bacteria.
4. Energy and Cost Efficiency
- High-efficiency motors, insulated tanks, and automatic control panels reduce electricity consumption and manpower requirements.
- Operators with knowledge of equipment functioning can maintain optimal energy usage.
5. Maintenance and Durability
- Materials like stainless steel require less frequent repairs and are long-lasting, even under acidic or alkaline cleaning agents.
- Understanding spare part availability, service intervals, and ease of maintenance reduces downtime and repair costs.
- Equipment should be selected considering local availability of service technicians and spare parts.
6. Compliance with Standards
- Proper knowledge helps in selecting equipment that meets national standards like BIS, FSSAI regulations, or ISO and Codex guidelines.
- Ensures that dairy operations are legally compliant and export-ready.
7. Adaptability and Scalability
- Selection must consider future expansion.
- Modular and scalable systems allow addition of new units without disturbing current production.
- For instance, modular milk cooling systems can be scaled from 2,000 litres to 10,000 litres with ease.
Conclusion
In milk processing, material selection ensures durability, hygiene, and product quality. Stainless steel (Grade 304 and 316) is the most preferred material due to its resistance to corrosion and ease of cleaning. Other materials like plastic, rubber, aluminium, and glass are used in specific components. However, choosing the right equipment goes beyond material—it requires understanding processing requirements, product volume, technical specifications, and maintenance practices.
Proper knowledge helps dairy managers and operators to make informed choices, thereby ensuring efficient performance, low maintenance cost, product safety, and regulatory compliance. This leads to a successful and sustainable milk processing operation.