Texture changes
Look for thinning, thickening, graininess, loss of body or delayed recovery after filling.
Product behaviour
Filling shear-sensitive pastes, creams and structured products.
A product may pump easily yet lose texture, entrain air, split, warm or damage inclusions as it passes through a filler. Selection should therefore test product condition before and after the complete wetted path.
Beyond a viscosity number
Separate resistance to flow from sensitivity to the way the product is moved.
Quoted viscosity can help describe a product, but it does not show whether repeated pumping changes its structure. The trial should reproduce the expected feed, valve, chamber, hose, nozzle, recirculation and agitation conditions rather than testing only a short open discharge.
Air and appearance
Check bubbles, foaming, voids, surface finish and whether the fill settles differently from the original product.
Temperature rise
Record product temperature where friction, heated feed or long recirculation could change viscosity or quality.
Inclusion integrity
Inspect particles, fibres or pieces before and after valves and nozzles for breakage, separation or blockage.
Technology comparison
Compare methods under the same product, dose and pack conditions.
The table is qualitative. Final suitability depends on the actual product, machine geometry, speed, materials, cleanability and test evidence.
| Method | Potential strengths | Questions to prove |
|---|---|---|
| Piston filling | Defined displacement, broad dose options and positive handling of many thick products. | Can the chamber refill consistently? Do inlet and outlet valves pass the product without damage or blockage? Does rapid acceleration change texture or introduce air? |
| Rotor-lobe pumping | Continuous feed and a relatively open product path can suit some viscous or particulate products. | What speed is needed? Does the product tolerate the clearances and repeated passes? Is there recirculation, and how does it affect temperature or structure? |
| Progressive-cavity pumping | Steady positive displacement can provide controlled flow for some difficult products. | Are stator and product-contact materials compatible? What happens during dry running or starvation? Can the product path be cleaned and inspected as required? |
| Other pump routes | Gear, diaphragm or other methods may suit a particular product and duty. | Compare shear, pulsation, leakage, particle passage, accuracy method, cleaning and maintenance using the real application rather than a generic pump claim. |
Representative trial
Test the product condition as well as the fill quantity.
Prepare a reference sample that has not passed through the filler. Compare it with samples taken after priming, during stable running and after the product has remained in the hopper or product path for the expected residence time. Record product temperature and machine settings for every comparison.
Where quality is assessed by viscosity, texture, microscopy, particle distribution, density, colour or another laboratory method, agree the method and acceptance criterion with the product owner before the trial.
Trial checklist
Include the hardest normal condition.
- Normal and boundary product temperatures approved for filling.
- Longest expected product residence or recirculation time.
- Largest normal inclusions and representative concentration.
- Lowest and highest required dose using actual containers and nozzles.
- Startup, restart and end-of-batch product where behaviour may differ.
Machine details that affect shear
Review the whole product path, not only the pump name.
Pipe and hose bore, bends, restrictions, valve openings, nozzle diameter, fill profile, pump speed, agitation, feeding pressure, suction conditions and recirculation can all influence product condition. A slower setting is not automatically gentler if it increases residence time or causes starvation.
Compare the positive-displacement filling options, use the product sample test guide, and review cream and gel filling or products with particles where those requirements apply.
Need to protect product texture during filling?
Send a representative sample, the approved filling temperature, dose range, container opening and the quality checks used for the finished product.
Compare texture at a defined time after filling
A cream or paste can look thinner immediately after pumping and recover part of its structure while standing. Other products may show a persistent change. Those outcomes should not be judged from samples observed at different times: a freshly filled jar and a reference left on the bench for an hour are not a controlled comparison.
Ask the product owner to define when texture, appearance or viscosity will be assessed after filling. Keep the sample temperature, handling and test method consistent, and compare a reference with samples from the proposed machine path at the same stated times. For a product known to recover after shear, the agreed observation period should reflect its intended manufacturing and packing process. The supplier should not choose a favourable waiting time after seeing the results.
Use these observations alongside dose repeatability and nozzle cut-off. A setting that produces an attractive immediate surface may still give a different settled texture, while a temporary change may be acceptable if the product meets its defined quality criteria. Retain samples from the normal operating condition and the longest routine hold in the equipment. This helps the product owner approve a filling method based on finished-product behaviour as well as whether the paste can be pumped.
Does thinning during pumping always mean a paste has been damaged?
No. Some materials show time-dependent recovery after shear. The product owner should assess samples using an agreed method and observation period.
When should cream viscosity be measured after a filling trial?
Use a defined time and temperature chosen before testing, consistent with the product’s quality method. Compare like-for-like reference and filled samples.
Set up a representative paste trial Review cream and gel filling routes