Filling and Sealing Packaged Foods
Practical Action
Sealing plastic or glass bottles and jars
Details of sealing glass containers are given in Technical Brief: Packaging Foods in Glass.
Bottle and jar closures can be grouped into three categories:
1. Pressure seals, used mostly for carbonated beverages. They include:
Screw caps.
Crimp-on lever-off (‘crown’ caps), or crimp-on screw-off steel caps. Crown caps can be
sealed using the equipment shown in Fig. 5.
Roll-on screw-off aluminium caps. Roll-on screw caps can be fitted using a manual capper
(Fig. 6) (also Roll-on-Pilfer-Proof (ROPP)) aluminium caps).
Cork or polyethylene stoppers.
2. Normal seals, used for non-carbonated liquids (e.g. milk or wines):
Pre-threaded, aluminium screw caps.
Lug type screw twist-off steel caps. These ‘Omnia’ caps can be fitted using a simple
manually operated capper (Fig. 7).
Press-on, prise-off plastic caps.
Push-in pull-out, or push-on pull-off caps, such as cork or synthetic stoppers. Corks can be
inserted by hand after soaking overnight in clean water, or using a corking machine (Fig. 8).
3. Vacuum seals, used for hermetically sealed jars:
Screw-on twist-off or screw-on screw-off caps.
Press-on prise-off, or press-on twist-off caps.
Crimp-on prise-off caps.
Screw caps are usually hand fitted in small-scale operations.
In each type of closure the seal is formed by pressing a cushioning material against the rim of
the container. The pressure must be evenly distributed to give a uniform seal around the rim.
Typically, the cushioning material is made from plastic, cork or paperboard.
Fig. 5. Different types of Crown cappers
Photo from Peter Fellows
Fig. 6. Manual roll-on screw capper
Fig.7. Manual ‘Omnia’ capper
Fig. 8. Corking machine Photo from Peter Fellows
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