Refrigerated and frozen foods like pizza, ready-to-eat meals, ice cream, orange juice, yogurt, and string cheese are top choices among consumers for both taste and convenience. As the popularity of these foods has grown, food processors have increased the variety of offerings in this area. Today, the refrigerated and frozen foods section of a supermarket includes items as diverse as corn dogs, quiche, and mini-cheeseburgers.
But refrigerated and freezer conditions present challenges for a packaging line - particularly with regard to the printing of variable data information, such as bar codes, lot codes, and expiration dates. Applications with the presence of condensation and frost, or those that involve washdown procedures, require extra consideration when choosing the right coding technology for the job.
The two most common primary package coding technologies used in refrigerated and freezer applications are small character continuous, ink jet printing and laser coding, each better-suited for certain substrates and environmental conditions. Manufacturers coding on packaging for refrigerated and frozen foods must take into account multiple factors when choosing which printer technology will best-suit their needs, such as:
- Type of material being marked
- Code durability
- Code adhesion in cold temps
- Printer cleaning and start-up cycle in a cold environment
- Regulatory compliance
Laser coding
Laser coders are a good choice for many refrigerated or frozen food product packages because their mark is permanent. Thus, it does not wear or smudge. This technology is ideal for coated and uncoated paperstocks as well as plastic containers. The two most common methods of marking primary product packaging with modern, sealed CO2 laser coders are ablation and surface modification. In the ablation method, heat from the invisible laser light is focused on the package, resulting in removal of a small amount of material from the surface. The second method, surface modification, physically alters the surface of a product or package to create the code.
Steered beam laser coders mark characters as a solid line for a clear, readable code, which is important when variable data is printed on packaging, such as a marketing message or product identification. These characters can be aesthetically pleasing, which is particularly important when incorporating marketing messages or product identification into the package design.
Because they generate heat, laser coders do not require special considerations for marking in cold temperatures. Some laser coders can be rated to an operating temperature of 32°F. They also do not use a consumable supply of materials for marking, such as ink or ribbon, which can be adversely affected by cold temperatures.
However, not all packaging substrates are ideal for laser coding. For example, a laser coder may not create enough contrast for a code to be seen on clear packaging or may burn thin plastic film. Without clear contrast, codes can be hard for consumers to find or may not be easily readable.
Ink jet printing
If a facility codes on a wide range of materials, continuous ink jet printers may offer necessary flexibility. Small character continuous ink jet printers deliver a stream of ink drops via a printhead to the package. This allows codes to be applied in a variety of fonts, lines and directions and at a range of throughput speeds - up to 1,000 feet per minute and with code heights ranging from 1/32 inch to taller than ½ inch.
Small character continuous ink jet printing can be a major asset in refrigerated and freezer environments because it can mark virtually any packaging substrate, from paperstock boxes and cartons to plastic films. Ink jet printers are a good option for marking on substrates not appropriate for laser coders, such as clear plastic films. Inks are typically available in a range of colors, thus eliminating contrast concerns that may be presented by laser coders.
Some inks are chemically engineered to be condensation-resistant. Such inks maintain code clarity even on products that will be stored in a refrigerator or freezer and might be subject to condensation or frost. Inks also can be specially formulated for adhesion in moist conditions, while other "food grade" inks are even formulated for marking directly on meat.
Deploying an ink jet printer in cold environments requires preparation. At temperatures cooler than roughly 40°F, ink viscosity increases, which affects print quality. Frozen food processors can house ink jet printers in environmental cabinets that maintain a temperature warmer than 40°F, so ink maintains appropriate viscosity. However, in refrigerated environments, ink jet printers tend to run long shifts, thus continuously circulating ink. The continuous flow of ink helps regulate the viscosity, avoiding problems that can lead to more frequent printhead cleanings, printer fluid purging and loss of productivity. Running the printer continuously also ensures that make-up fluid is constantly added to the ink to keep it from thickening.
IP65 or IP54 rating?
The washdown rating of coding equipment, which is defined by the International Electrotechnical Commission (IEC), also may be necessary in many refrigerated and frozen applications. An Ingress Protection 65 (IP65) rating means a coding system is both dust-tight and protected against water jets or condensation that can be created by changing temperatures in the environment. An IP54 rating means the equipment is protected only against dirt and splashing water.
The most appropriate IP rating is determined by the type of product being packaged and the ratings of other nearby processing and packaging equipment. For example, an ice cream filling station needs to be sterile, which requires washdown that may use chemicals that eliminate bacteria, so an IP65 rating is necessary. Conversely, by the time a frozen pizza reaches an ink jet printer, it has already been placed on a flat and wrapped in plastic film, so an IP54 rating is sufficient.
Be prepared
To gather enough information to make the most astute choice when it comes to variable data marking and coding equipment, manufacturers should ask multiple suppliers for product demonstrations and should insist on several samples of coding on different substrate types. Samples from multiple suppliers should be compared in order to choose the technology that provides the highest-quality, clearest codes. Manufacturers also should ask the supplier if it is possible to install a trial printer in their facility to test it in the actual environment and ensure that the technology is appropriate for the facility's parameters, such as temperature, run-times and substrates. Such a trial also can ensure the printer will fit with other operating procedures. By being prepared to discuss a facility's specific needs, there can be a proper evaluation of the most appropriate coding solutions, which ultimately will maximize both uptime and productivity.