Can a Container Label Be Applied After the Container Is Filled?
At what stage should container labeling be part of your production line? Is it useful to label the container first for internal tracking? Can filling a container with a food product damage the label or make it harder to apply afterward?
Here’s what you should consider about labeling containers after filling when you’re using your in-line labeling system.
The Right Time to Label: Label Accuracy and Internal Tracking
Product and shipping labels are used by people outside your facility (including retailers and the end-user), so choosing when to label is mostly a matter of surface compatibility and validity. Labels need a clean, dry surface in order to stick and must then survive further processing. If you’re printing unique additional information on each container, like lot numbers and best-by dates for shelf life, you need to be sure the information won’t change if there’s an interruption in production. For most products, it makes sense to add a label after the container is filled.
However, you may use labels for internal tracking, as well. For example, if you need to pack several items in the container, you can add a label with a barcode or other identifier at the start. This lets you monitor the container’s status as it moves through your system.
Each time something is added to the container, the barcode is scanned and checked off the packing list. If it’s scanned at the wrong point in the packaging line, it can be flagged and checked for missing items. Need to add a shipping label to the packaging materials? You can use this ID label to add the correct address. Just scan the box to pull up the address in your system, then send it to the shipping labeler’s PLC. From there, it can print and apply the correct shipping label.
Hot Sterilization Processes and Container Labeling
For many foods, the best way to reduce pathogen growth in storage is by using heat. Depending on the acidity of the product, this is achieved with hot fillers and retort processing.
Hot filling is mostly used for acidic products stored at ambient temperature. Foods with a pH under 4.6 are already a hostile environment for contagions, so heat kills any remaining pathogens, creating a sterile environment inside the container.
The hot filler liquid is heated to 194°F (90°C) and then poured into the container. Once the container is sealed, it’s tilted for the liquid to make contact with the entire interior. The heat sterilizes the surfaces inside the container. Once sanitized, the container is cooled by water sprayed through a cooling tunnel. An air dryer removes water from the surface.
Hot filling is the preferred sterilization process for acidic products because it requires no additional preservatives and has minimal impact on flavor and nutrient content. Tomatoes are acidic enough for this process to work, as are most sodas, citrus juices, sports drinks and teas.
Backup systems must be in place to ensure the product is at the correct temperatures throughout the process. If the temperature is too low initially, the resulting product can grow contagions, making it a health and safety risk. If the product isn’t cooled quickly enough, it could affect quality. The production system must keep the container at maximum temperature for 15-30 seconds and above 180°F (82°C) for another two to three minutes for this process to be effective.
Hot-filling machines are compatible with glass bottles as well as heat-resistant cans and glass bottles. By the time the container has passed through the air dryer, the surface should be cool and dry enough to work with most labels. Most thermal paper labels are stable up to 212°F (100°C), so they won’t discolor when applied to a warm container. Likewise, many adhesives, including common acrylics, have no problem working at these temperatures. While it is feasible to label containers when they’re empty, there’s always a chance that the product will drip onto the label during filling.
Low-acidity products can be sterilized with retort processing, which heats the entire packaged food. This requires higher temperatures than hot filling, potentially affecting the food’s flavor. In fact, some processes use the retort to cook products after the packaging process. These sealed containers are subjected to hot steam, a hot water bath or a spray that combines steam and hot water, bringing the product’s temperature up to pathogen-killing levels.
Steam-based retort processing can deform flexible containers but works well with rigid cans and bottles. Most labels and adhesives can’t withstand the extreme heat and moisture in the retort, so it’s better to label products after processing.
Labeling Cold Products
While both the label and adhesive need to be compatible with low temperatures, most application issues are caused by the adhesive. Cold surfaces don’t just make adhesives less pliable. They also collect moisture from the air, forming condensation. Surface moisture extends wet-out times and may keep the label from getting any adhesion.
Warmer air holds more moisture than cold air, so condensation may only be a problem in the summer. This is mostly an issue when bottling cold products like beer. An air knife can blow this moisture off the bottles before they reach the labeling machine.
Many adhesives can survive extreme temperatures once applied, but they have a limited application temperature range. In some cases, you may need to apply labels before filling. For example, emulsion acrylic adhesives have a Service Temperature Range (STR) as low as -65°F (-54°C), but their Minimum Application Temperature (MAT) is usually no lower than 0°F (-18°C).
You also need to consider the labeling equipment’s operating temperatures. Machines like our 360a Series have an operating temperature range of 41° F to 104° F (5° C to 40° C). This is a problem if you need to maintain the cold chain for temperature-sensitive products. Usually, the best solution is to add a heated cabinet or room to your cold storage area for the labeler. Products are only in this area long enough for label application, ensuring they won’t get warm enough to cause degradation.
If you want to know more about cold labeling, including choices for adhesives and backing, check out our blog article, “Considerations for Cold Temperature Labeling Solutions.”
Labeling Hazardous Chemicals
Inevitably, the type of product also determines when the container should be filled in the production line. Hazardous chemicals must be labeled before filling the container as required by the Hazard Communication Standard (HCS) from the Occupational Safety and Health Administration (OSHA). These regulations require that hazardous chemicals be properly labeled, tagged or marked with their identities before they are filled or used in the workplace.
The labels must be legible, prominently displayed on the container and have physical and health hazard information. This is to ensure that employees are aware of the potential hazards associated with the materials and can take appropriate precautions to protect themselves.
Labeling hazardous materials before they are filled ensures that the proper labeling is in place in case of accidental release or spill. Plus, it helps prevent mistakes in the filling process. Placing a printed label on the wrong product can be extremely dangerous.
Hazardous chemicals have their own labeling requirements due to their risk. These include denoting required information beyond the product name, like if the chemical is flammable, toxic, explosive or poses other health and safety risks. This required information must be included on any secondary container as well. Even if the product is a concentrate and put in a secondary container (such as a plastic bottle) to be diluted, include the same required information on this label as the original container. Don’t reuse a secondary container if it will not have accurate information.
You can find specific regulatory requirements at www.osha.gov/hazcom.
Labeling Solutions That Work With Your Labeling Requirements and Products
Whether you’re labeling contains after filling or before, CTM Labeling Systems has the equipment you need. Contact us, and we’ll put you in touch with one of our local equipment distributors. They’ll help you set up a labeling system that fits your products and your production system!