Extrusion

Extrusion testing is an essential method in the food industry for measuring the texture and flow behaviour of semi-solid and viscous products. It provides quantitative data on a product’s resistance to deformation under controlled force, enabling manufacturers to maintain consistent quality across batches. The method is applied to products such as sauces, gels, doughs, and pastes, helping to confirm performance before goods reach the consumer.

By simulating the forces that products experience during processing or consumption, extrusion testing enables engineers and food technologists to assess viscosity, cohesiveness, and other rheological properties. These parameters are critical in ensuring that food products meet both production and consumer expectations.

Extrusion testing involves forcing a food sample through a shaped orifice, grid, or opening while measuring the resistance to movement. This resistance reflects the texture and structural integrity of the product and is influenced by formulation, processing conditions, and storage history.

Extrusion testing is used to:

• Monitor batch-to-batch consistency
• Detect texture changes during product development
• Verify compliance with defined texture specifications
• Relate measurable properties to consumer sensory perception

Forward and back extrusion methods

Forward extrusion pushes the sample through an orifice or grid in the same direction as the applied force. It is ideal for products that pass through dispensing systems, such as spreads, pastes, and condiments, and provides data on flow ease and yield stress.

Back extrusion uses a probe to compress the product in a container, forcing the sample to flow around the probe and upwards. This method is well-suited to spoonable or pumpable products such as yogurt, custard, or dessert gels.

Key differences:

• Forward extrusion replicates conditions found in manufacturing processes involving piping or nozzle dispensing
• Back extrusion replicates consumer or service handling where the product remains in its packaging

The choice of method depends on product viscosity, packaging format, and the performance parameters required.

Extrusion testing supports both product development and quality control for semi-solids and viscous liquids.

Example applications:

• Measuring spreadability and pumpability in sauces and condiments
• Evaluating the filling performance of chocolate creams and confectionery pastes
• Assessing the firmness and cohesiveness of custards, yogurts, and dessert gels

By providing quantitative results, extrusion testing helps to refine formulations, improve processing efficiency, and reduce waste.

Rheology, the study of deformation and flow, is central to understanding extrusion behaviour. Key properties measured include:

• Viscosity: the product’s resistance to flow under applied force
• Yield stress: the minimum stress required to initiate flow
• Cohesiveness: the ability of the structure to resist breaking apart

Accurate measurement of these parameters enables manufacturers to:

• Optimise recipes for desired dispensing or spreading characteristics
• Prevent issues such as nozzle clogging or uneven flow
• Maintain texture stability throughout the product’s shelf life

Extrusion testing delivers measurable benefits for food production:

• Consistency control: Reduces variation between batches to within tight tolerance limits
• Process optimisation: Identifies ideal processing conditions for efficient production
• Waste reduction: Detects texture faults before packaging
• Regulatory compliance: Provides documented evidence of product conformity to specifications

Although there are fewer dedicated standards for food extrusion than for plastics or metals, recognised guidelines help ensure repeatability and comparability. Examples include:

• BS EN ISO 11036: Sensory analysis – methodology for texture profile evaluation
• AACC International methods: Applicable to texture measurement in cereals and bakery products
• Company-specific protocols: Developed for product and equipment consistency

These frameworks help maintain consistent methodology across production sites and laboratories.

Selecting the correct extrusion testing system involves matching the machine’s capabilities to the product type and testing goals. Key considerations include:

• Load capacity: to handle expected resistance levels for different viscosities
• Probe and orifice design: tailored to specific sample characteristics and method type
• Precision and repeatability: to ensure reliable results for quality control
• Food-contact compliance: ensuring all fixtures meet hygiene and safety standards

Specialised extrusion cells with interchangeable grids or orifice plates allow one system to test multiple product types efficiently.

Mecmesin offers precision-engineered extrusion testing solutions designed for food texture analysis, built on platforms such as the OmniTest and MultiTest-dV motorised test frames. These systems provide:

• Controlled loading rates for accurate flow resistance measurement
• High-resolution load cells for reliable force data
• Customisable fixtures for both forward and back extrusion methods
• Full integration with VectorPro software for real-time data capture, automated analysis, and compliant reporting

By combining precision mechanics, hygienic fixture design, and flexible test configurations, Mecmesin systems help food manufacturers achieve consistent quality and optimise production processes.

If you need to improve product consistency, optimise processing conditions, or validate your quality control methods, Mecmesin’s technical specialists can help. Our team will work with you to define the most suitable extrusion testing setup, ensuring reliable, compliant, and cost-effective results for your food manufacturing operation.