How to Ensure Accurate Piston Filling for Thick Juices

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Hot filling pasteurises the product and sanitises the bottle in one pass, which is why acidic juice and tea can be filled without a separate bottle steriliser. Factors such as viscosity, temperature, and container size play a significant role in determining the correct calibration settings.
Key facts at a glance
Valve typeHot-fill, up to 85 C
Rated output6,000-36,000 BPH at 0.2-2 L
ContainerHeat-resistant PET geometry, or glass
LineHot-fill monobloc with tunnel pasteuriser
ProductsJuice, tea, nectar, functional drinks
Key controlFill temperature, hold time, cap seal

Why does juice get filled hot instead of cold?

Hot filling does two jobs at once: it pasteurises the product on the way to the filler, and the residual heat sanitises the bottle and cap. That is why a hot-fill line can run an acidic juice without a separate bottle steriliser. The price is a heat-resistant bottle and a longer cooling tunnel.

Factors such as viscosity, temperature, and container size play a significant role in determining the correct calibration settings.

What breaks first on a hot-fill line?

Cap seals and filling valve O-rings, because they see the highest temperature every cycle. A seal that is fine on a water line at 20 C will harden in weeks at 85 C. The spare parts list should carry those two items in proportion to the number of valves, not as a single set.

RouteTemperatureWhat it costs
Hot fillUp to 85 CHeat-resistant bottle and a cooling tunnel
Cold fill with preservativeAmbientFormulation constraint, not a machine constraint
Cold fill with in-line pasteuriserProduct-side onlySeparate pasteuriser and a closed filling zone
Hot fill in glassUp to 85 CGlass mass, slower line, higher transport cost

A different bottle format means a different unit; see the Juice By Volumetric Filler.

How do you compare a hot-fill line with a cold-fill line?

Compare them on the product, not on the machine. Hot fill suits acidic juice and tea in heat-resistant PET. Cold fill needs a preservative system or a separate sanitising step, but it protects heat-sensitive flavours and vitamins and uses a lighter bottle. The decision is a product decision with a packaging cost attached.

Throughput and change-part lists are on the Hotfill Type Filling Machine for Juice page rather than in this note.

What does a tea line need that a juice line does not?

Tea usually needs finer filtration, deaeration to protect aroma, and a fill temperature that does not strip the volatile notes. Tea also clouds after cooling, so the clarification step is part of the product design, not a filling detail.

The same question is worked through from another angle in How to Improve Hotfill Juice Quality with Temperature Control.

How to read the numbers. The numbers in the tables are reference ranges taken from the product specification. A rated BPH covers filling only. Pasteurisation, hold time and cooling sit outside it, so size on 0.65-0.85.

Frequently asked questions

What temperature is juice hot-filled at?

Up to 85 C, set per product and per bottle. The exact set point and tolerance belong in the product specification, because acidity, pulp content and bottle wall thickness all move it.

Can hot-fill juice run in standard PET bottles?

No. Standard PET softens and deforms at fill temperature. The bottle needs a heat-resistant geometry, and the mould and preform are part of the project, not an afterthought.

Does hot filling replace pasteurisation?

It replaces the bottle steriliser for acidic products, because the fill temperature and hold time do the microbial work. It does not replace correct product formulation or a validated hold tube.

Can a hot-fill line run clear juice and pulp juice?

With a filter change and a different valve bore for the pulp, yes. Clear juice needs finer filtration, and pulp needs agitation in the bowl so the fibre does not settle.

Key takeaways
  1. Fill temperature is a product and package number, not a machine setting.
  2. Cold filling moves the microbial control from the filler to the product and the plant.
  3. A change of fill temperature invalidates the shelf-life trial.
  4. Cool the bottle on a ramp, not a plunge.
About the author
Written by the Sunswell engineering team - led by Howie SUN, Founder & CEO, with 14 years in filling and blow-moulding equipment R&D and turnkey project delivery across 71+ countries.
Last reviewed: 2026-08-28 . Reviewed by Sunswell engineering team
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