How to Pump Chocolate: Best Practices for Success

Pumping chocolate is a delicate process that requires experience, precision, and careful attention to detail. Unlike other food products, chocolate presents unique challenges due to its sensitivity to shear, temperature, and pressure. Below are key guidelines to ensure smooth and effective chocolate pumping.

Chocolate is highly shear-sensitive, meaning excessive speed or pressure can cause cocoa butter separation, leading to serious production issues. When this happens, the cocoa butter can crystallise and form an abrasive, sand-like substance that can damage equipment and compromise product quality.

Never exceed 150 RPM, with optimal speeds often around 40-50 RPM to prevent shear damage. Some may argue that speeds up to 300 RPM are acceptable, but this is a risky approach.

Keep discharge pressure below 7.0 bar to prevent excessive back pressure. Using the  All-Pumps Friction Loss Calculator  can help in accurately calculating back pressures. In cases where long pipe runs are necessary, increasing the pipe size beyond what seems reasonable may be required.

Temperature consistency is critical for maintaining chocolate’s texture and quality. A minor deviation can cause crystallisation issues.

Typically, chocolate needs to be maintained at 46 °C, but this can vary by formulation.

Every part of the pump end should be jacketed, including the bowl, front plate, and gland. Pumps like Mouvex, which lack adequate jacketing, have failed in the past due to insufficient temperature control.

Avoid steam or electric heating, as these methods can cause overheating and damage the chocolate.

The best option for chocolate pumping is a jacketed packed gland, which will leak but can be managed with proper containment systems. A double mechanical seal with a pressurised barrier is an alternative, though it is costly, complex, and difficult to maintain.

Power requirements for chocolate pumping can be deceptively high due to its viscosity.

Design your drive system to handle up to 16 bar pressure at maximum viscosity (1,000,000 cPs). This ensures that nuisance trips are avoided.

Design your drive system to handle up to 16 bar pressure at maximum viscosity (1,000,000 cPs). This ensures that nuisance trips are avoided.

Chocolate is denser than many other fluids, so always account for its SG in calculations to avoid misjudging the required pump power and pressure.

For most chocolate applications, the following pump configuration works best:

• Pump Type: "Choc Spec" internal gear pump, such as Roper or Tuthill Gear Pump
• Material of Construction: Fully cast iron
• Shaft Seal: Food-grade packed gland
• Jacketing: Pump head and gland must be jacketed
• Clearances: Extra-large clearances with circulation galleries and specialised materials
• No Pressure Relief Valve: Not needed in chocolate applications
• Drive System: Inline geared motor drive with a tyre-flex coupling on a rigid stainless-steel base

When sourcing a pump, insist on a "Chocolate Spec" model to ensure it meets all necessary design parameters. While there may be rare instances where deviations are needed, these rules should generally be adhered to for optimal results.

For a real-world example of successful chocolate pumping, check out this case study on Roper Chocolate Gear Pumps Set Up for Conching Machines. This case highlights how the right pump selection and setup contribute to efficient and reliable chocolate processing.

Roper Chocolate Pumps are specifically designed to handle a wide range of applications in chocolate processing, including chocolate liquor, dark chocolate, and various sugar solutions. Key modifications that make these pumps ideal for chocolate applications include:

• Iron bearings with large square grooves  for improved process fluid circulation and to prevent build-up (optional carbon bearings available).
• Lantern ring in the packing  to prevent air entry, reducing the risk of chocolate hardening inside the pump.
• Undersized gears for extra clearance in hardened iron alloy as standard or stainless steel as option.
• Optional jacketed pump design to maintain optimal temperature control.
• Additional customisation options, such as PTFE packing, aluminum gaskets (for high-temperature applications), lube fittings to all bearings, and internally jacketed backplates & faceplates for precise temperature management.