In commercial canning, some of the most important details are also the easiest to overlook. Headspace is a good example. It is simply the space between the surface of the product and the inside of the container lid, but that relatively small area can play an important role in the overall packaging and processing system.
The appropriate headspace depends on the product, container, filling process, and established thermal process. It can influence vacuum development, product expansion during heating, and the way a container behaves during processing and cooling.
For commercial food producers, understanding headspace is therefore part of developing a repeatable production process rather than simply deciding how full a can should look.
What Is Headspace in a Can?
Headspace is the unfilled space remaining above the food or beverage after a container has been filled and before it is sealed.
It might seem logical to fill every container as completely as possible. After all, unused space can appear inefficient. In commercial canning, however, the correct fill level should be based on the requirements of the product and validated process rather than appearance alone.
Food products can expand when heated. Gases and vapours within the container can also respond to changes in temperature and pressure during processing.
Providing the specified headspace gives the product room to behave as expected during these changes.
Too much or too little headspace can alter conditions inside the package. This is one reason fill levels should be controlled consistently throughout production.
Headspace and Vacuum Formation
Headspace is closely connected with the development of vacuum in many canned products.
During processing, air and gases may be removed or displaced from the container. As the sealed container subsequently cools, the contents contract and a vacuum can develop.
Depending on the application, manufacturers may use line exhausters before seaming to help remove air from filled containers and support vacuum formation.
The objective is not simply to create the largest possible vacuum. The appropriate conditions depend on the product, package, and established process.
Headspace, product temperature, exhausting, and sealing all interact. A change in one part of the process can therefore affect another.
Dixie Canner also offers vacuum and pressure test gauges that can be used as part of quality-control procedures where vacuum or pressure measurements are required.
Allowing for Expansion During Thermal Processing
Headspace becomes particularly important when containers are thermally processed.
Dixie Canner has been manufacturing RDSW-3SS retorts for food processing since the early community canning programs developed with the University of Georgia in the 1920s. These vertical, still retorts are designed for processing under pressure and can be used with cans, glass containers, retortable pouches, and retortable trays.
As a product heats during a scheduled thermal process, the product and gases within the package can expand. Pressure conditions can change as well.
The correct headspace is one component of ensuring the package performs as intended during these conditions.
Dixie’s RDSW-3SS Retort is available with both manual and automatic retort control systems and supports applications including R&D and pilot programs, specialty product processing, cold brew coffee and beverage production, and package-integrity testing.
The processing schedule itself must be established for the specific food and package. Headspace should likewise follow the requirements established for that process rather than being determined through guesswork.
Headspace Works Together With Proper Seaming
Correct headspace does not replace a properly formed double seam, and a good seam does not compensate for an improperly controlled filling process.
After filling, a can seamer mechanically joins the can end to the body to create the double seam. This seam must meet the specifications established for the particular can and end being used.
When fill levels vary significantly, product may get into areas where it can interfere with clean container handling or seaming. Overfilling can also create unnecessary mess around filling and seaming equipment.
This makes consistency especially important.
Operators should establish filling procedures that repeatedly produce the specified fill weight or volume and headspace. The seam itself should then be checked using appropriate double seam test instruments and the specifications provided by the container manufacturer.
Together, controlled filling and proper seaming create a much more predictable packaging process.
Why Consistency Matters on a Production Line
A few containers filled by hand may be relatively easy to monitor individually. Commercial production changes the equation.
When dozens, hundreds, or thousands of containers are being processed, small variations can become recurring production problems.
For example, inconsistent product portioning can create different headspace levels from one container to another. Variations in product temperature can also affect conditions within the package. Thick sauces, soups, vegetables, seafood, beverages, and other products may behave differently during filling and processing.
This is why producers need to think about the complete food processing equipment system rather than treating each machine as an isolated component.
Preparation, filling, exhausting, seaming, retorting, cooling, and inspection should work together as a controlled process.
Maintaining repeatable conditions also makes troubleshooting easier. When fill level, product temperature, container specifications, seam measurements, and processing conditions are documented, operators have useful information to review if results begin to change.
Headspace Should Be Established for the Product and Process
There is no universal headspace measurement that should be applied to every commercially canned food.
Different foods behave differently. Containers vary in dimensions and materials. Processing methods vary as well. A glass jar, metal can, pouch, and tray may each have different package requirements.
For shelf-stable foods requiring thermal processing, producers should work with a qualified process authority or other appropriate food-processing professional to establish the scheduled process and relevant production parameters.
Equipment manufacturers can help producers select machinery capable of carrying out the required operations, but food safety parameters should come from the appropriate processing authority.
This distinction is particularly important for startups. A recipe that works well in a kitchen cannot simply be scaled up and canned commercially without considering how the product behaves after filling, sealing, heating, and cooling.
Small Details Make a Difference in Commercial Canning
Successful commercial canning depends on controlling many interconnected variables. Headspace is one of them.
When the correct headspace is combined with consistent filling, appropriate exhausting where required, properly adjusted can-seaming equipment, verified double seams, and an established thermal process, producers can create a much more controlled and repeatable operation.
Dixie Canner has been manufacturing can seamers and food processing equipment in Athens, Georgia since 1895 and has been fabricating RDSW-3SS retorts since the early 1920s. Our equipment supports commercial processors, specialty food companies, community canneries, R&D facilities, pilot plants, beverage manufacturers, and other operations requiring dependable canning and thermal-processing equipment.
Talk to Dixie Canner About Your Canning Equipment
Whether you are developing a new canned product, improving an existing production line, or selecting equipment for filling, exhausting, seaming, or thermal processing, Dixie Canner can help you identify equipment suited to your application. Explore our commercial canning equipment or contact our knowledgeable team to discuss your production requirements. Call (706) 549-1914 or email sales@dixiecanner.com to speak with Dixie Canner about your canning operation.
Frequently Asked Questions
What is headspace in commercial canning?
Headspace is the unfilled area between the surface of the product and the inside of the container lid. The appropriate amount depends on the food, container, filling method, and established processing requirements.
Why is headspace important during thermal processing?
Food, gases, and vapours can expand as a container is heated. The specified headspace provides room for these changes and is one of several factors involved in how the package behaves during processing and cooling.
Does headspace affect vacuum in canned foods?
Headspace can influence vacuum development along with factors such as product temperature, exhausting, sealing, and cooling. The desired conditions should be established for the particular product and process.
Can too little headspace cause problems?
An improperly controlled fill level may affect how the container behaves during processing and can contribute to messy filling or product entering areas where it may interfere with container handling and seaming. Producers should follow the headspace specified for their process.
How do I determine the correct headspace for my canned product?
There is no single headspace measurement suitable for every canned product. For products requiring a scheduled thermal process, work with a qualified process authority or appropriate food-processing professional to establish the requirements for your specific food and package.
