Extrusion is one of the most versatile processes in food manufacturing, producing everything from breakfast cereals and snack foods to pet food and animal feed. But the intense combination of heat, shear, and pressure makes starch transformation notoriously difficult to control. The Rapid Visco Analyser (RVA) provides a fast, reliable way to measure the degree of cook in extruded products, giving process engineers the data they need to optimise extrusion parameters and maintain consistency. It serves manufacturers across food and feed — breakfast cereal and snack producers, pet food manufacturers, and aquaculture and animal feed producers — together with the ingredient suppliers providing the starches and grains that determine extrusion performance.

Industry Challenges
 

• Starch degradation during extrusion is highly sensitive to screw speed, barrel temperature, moisture, and feed rate — small changes can significantly alter product texture
• Degree of cook is difficult to measure quickly, leading to delayed feedback and wasted product during process optimisation
• Raw material variability (especially starch content and quality) affects extrusion outcomes unpredictably
• Pet food has species-specific starch cooking requirements — cats cannot digest raw or retrograded starch, while dogs tolerate partially uncooked starch, demanding different process targets
• Consumer expectations for consistent texture in cereals, snacks, and pet food demand tight process control

How the RVA Solves These Problems

The RVA measures the residual viscosity of extruded products by re-pasting them through a controlled heating and cooling cycle. The key insight is simple: the more thoroughly cooked an extrudate is, the less residual viscosity it develops when re-tested. This gives you a direct, quantitative measure of the degree of cook — in about 20 minutes.

For breakfast cereals and snacks, this means you can rapidly map the relationship between extrusion parameters and product quality. If your cereal is going soggy too quickly in the bowl, the RVA will show you why — a high cold-water swelling peak indicates over-processed starch. Adjust your screw speed or barrel temperature, re-test, and verify the improvement before committing to a full production run.

For pet food, the RVA is essential for hitting the right degree of cook for each species. Cat food requires fully gelatinised starch because cats lack the enzymes to digest raw starch — feeding them undercooked product can make them ill. Dog food can tolerate a lower degree of cook. The RVA lets you set and verify different process targets for each product line, and catch any drift before it becomes a quality issue.

The same approach works for animal feed, where starch in wheat or other grains binds extruded pellets and controls their density and integrity. The RVA screens incoming grain quality and verifies that the extrusion process is delivering the right degree of cook for pellets that hold together as intended.
 

Related RVA Methods

The RVA comes with a library of standard methods that can be used as-is for known applications, or as a starting point for developing your own product-specific test profiles.

*Requires the RVA 4800, which provides high-temperature testing up to 140°C.

  Key Benefits 
 

• ✓ Quantitative degree-of-cook measurement in 20 minutes — fast enough for process optimisation trials
• ✓ Objective comparison of extruded products across lines, facilities, and suppliers, including external and competing products
• ✓ Species-specific process control for pet food — verify cooking targets for cats, dogs, and other animals
• ✓ Dual indices (cold peak and final viscosity) capture both texture and overall cook level
• ✓ Works across breakfast cereals, snacks, pet food, animal feed, and aquaculture pellets