Pet Food Co-packer is First with Retort Cartons

One of the engineers who developed Tetra Pak’s retort carton platform, Pawel Marciniak has built his co-pack/co-man business for premium pet food NaturPak Pet on the technology—with considerable success.

Pawel Marciniak is one of Tetra Pak’s biggest fans. He’s such a fan, in fact, that he and his wife, Iwona, built two extremely successful co-packing businesses based around the company’s Tetra Recart® retort carton technology. It’s really no surprise though—Marciniak was not only an employee of Tetra Pak from 1992 to 2006, but he was also one of the engineers responsible for developing and implementing the Tetra Recart platform as an alternative to cans for wet, shelf-stable foods.

“After I was with Tetra Pak in the U.S for six years working on this new processing and packaging platform, my wife and I fell in love with it, so we decided to invest all our money in building the platform,” says Marciniak. “And the idea was very, very simple—to educate smaller brand owners and also retail stores on the technology and help them start using it for new products.” 

In 2007, the Marciniaks launched IPM Foods, in Beloit, Wis., to co-manufacture soups, gravies, and sauces for human consumption using the Tetra Recart system. It wasn’t long though before the company started experimenting with wet pet food. Says Marciniak, while the processing and packaging technology was the same, creating pet food required the development of recipes that could provide a complete and balanced meal in one serving versus providing just one part of a meal, as for humans.


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He adds that early on he saw the need in the U.S. market for less processed pet food. “Less processed means let’s not take the water out of the product because it’s easy for transportation and for storage,” he says. “Let’s retain the same nutritional value as from the beginning.”

Recognizing the opportunity to provide brand owners and retailers with premium and super-premium wet dog and cat food—in sustainable packaging no less—the Marciniaks started up their second business, NaturPak Pet, in 2020. The new company is located in Janesville, Wis., not far from IPM, which relocated to that city in 2017.

Fulfilling Marciniak’s prediction that the natural pet food market was set to explode, demand for NaturPak’s services has been exceptional. Currently producing 80 million units of pet food annually, the company plans on adding an additional 40 million units of capacity in 2022, with a potential additional capacity of 80 million in the facility—all of which is powered by the Tetra Recart platform.

Retort cartons a sustainable alternative to cans

Tetra Pak is known for its aseptic food processing and carton packaging systems. With the aseptic process, the packaging material is sterilized before filling, which is done in a fully sterilized environment, resulting in a product that is preservative-free and shelf stable for up to 24 months. The process allows the food to retain its color, texture, taste, and nutrition. Tetra Pak’s flagship package is a multilayer carton, made primarily from paper, with layers of polyethylene and aluminum for barrier.

With the Tetra Recart, Tetra Pak developed a carton and packaging system that could handle wet foods traditionally packaged in cans that require in-pack retort cooking and sterilization. To withstand the high temperatures—from 212°F to 266°F—and wet conditions used in the retort process, Tetra Pak reengineered the carton structure with a unique paperboard material with special sizing and new polypropylene-based polymer grades. The Tetra Recart was introduced with the tagline, “Canned food—two centuries smarter.”

What makes the retort carton “smarter,” according to data from Tetra Pak and from those who work with the system, such as Marciniak, is the range of sustainability and marketing benefits versus cans—and versus glass jars and pouches. “It’s just progress; it’s better packaging,” says Marciniak. “Every so many years, we face a new type of packaging. In the 19th century, there was the three-piece can, which was good at the time, considering the technical development of society. Then, from three-part cans, they moved to two-part cans with an easy opening feature, and then there were pouches, and then Tetra Pak moved packaging a bit further—pouches with support.” 

Collapsing the top and bottom of the carton, Marciniak demonstrates his point, as the carton lies flat. But compared with a flexible pouch, he notes, the Tetra Pak carton is easier and more economical to transport, easy to stock on a shelf, and easy to open and close. It also provides a better billboard space for marketing.

NaturPak offers all five of the available Tetra Pak retort carton sizes; a 100-mL size will be joining the lineup next year.NaturPak offers all five of the available Tetra Pak retort carton sizes; a 100-mL size will be joining the lineup next year.While sustainability proponents may focus on the carton’s lower recycling rate versus the can, according to Tetra Pak, when analyzed across its lifecycle, the multilayer carton offers a footprint that is 81% lower than those of steel cans and glass jars. 

Enumerating the Tetra Recart carton’s sustainability benefits, Tetra Pak relates that the package is made from 70% renewable material, sourced from Forest Stewardship Council (FSC)-certified sources, resulting in a carbon footprint that is five-times lower than cans. The Tetra Recart package also weighs approximately 60% less (for a 400-g pack) than a can. Because of its light weight and rectangular shape, six- to 10-times more empty retort cartons can fit on a single truck versus cans. Similarly, with filled cartons, 10% to 20% more units can fit on a truck for outbound distribution. These factors result in reduced transportation costs and fewer resulting carbon emissions. 

The Tetra Recart offers functional benefits too. For brand owners, the carton’s rectangular shape means it takes up 30% less shelf space, allowing CPGs to gain more retail space. In addition, its flat surface offers a larger area in which to communicate marketing messages. For consumers, the package presents no sharp edges, and its laser-perforated, easy-open feature allows it to be opened without a can opener.

Marciniak also believes the carton eliminates the metallic taste and smell imparted to products packaged in cans. “That could be a very subjective observation, I don’t have scientific evidence to prove this,” he says. “But definitely, the perception at the consumer level is [the product is] fresher from the box.”

NaturPak hits the ground running

A greenfield plant, the NaturPak facility spans 180,000 sq ft, with additional land available to expand. The company employs from 50 to 60 people, with a goal to grow to 100 employees by the end of 2022. Its customers and those interested in NaturPak’s services include “everyone throughout the market,” including startups, retailers, and multinationals, Marciniak says. “Again, there was a void in the industry of good, wet pet food packaged in sustainable packaging.” Not only are companies looking for a source for premium and super-premium pet food, but some have also been facing difficulties getting enough cans for their products, so they’re switching to cartons. 

One of the biggest differentiators between NaturPak and other pet food co-mans/co-packs, explains Marciniak, is the way it manufactures the pet food through a small-batch process that enables it to create specific textures and flavors for different pet preferences. “The small-batch process allows us to have better control of the product,” he explains. By mixing the highest-quality meats, vegetables, and supplements in small-batch kettles designed in-house, NaturPak is able to produce pet foods that are as appealing in appearance as they are in taste, with whole ingredients—for example, beans, blueberries, or meat—visible in the final product.

“At the end of the day, we are judged many times,” says Marciniak. “First, when the package is opened, on the aroma that comes out. Then, what the product looks like when it’s put on the plate—that’s by the owner. Then, if that pet eats the product and how they like it. And finally, when the dog leaves droppings, the owner will judge whether they are of the right consistency.”

The Tetra Pak R2 carton filling machine was chosen for its speed of 6,000 packs/hr, which allows for efficient, small-batch product processing.The Tetra Pak R2 carton filling machine was chosen for its speed of 6,000 packs/hr, which allows for efficient, small-batch product processing.To keep control of the small-batch process and maximize equipment efficiency during filling, NaturPak opted for Tetra Pak’s lower-capacity retort filling machine, the Tetra Pak® R2, at 6,000 packs/hr, rather than the higher-speed, 24,000-pack/hr R1. “We chose this from the point of view of control over the delivery—to be able to create smaller batches and control the ingredients,” explains Marciniak. “It also allows our clients to be more diversified in different flavors with a smaller minimum, so they can test the market response for certain flavor profiles.” He adds that a minimum run can be as low as 35,000 units, but the company’s “sustainable range for production is 75,000 units.”

NaturPak offers the full gamut of Tetra Recart cartons sizes, which includes the 200-mL Mini carton, and the 340-, 390-, 440-, and 500-mL Midi carton sizes. In 2022, Tetra Pak will be launching a new size, a petite, 100-mL carton to compete with the 3.5-oz cans used for cat food. NaturPak plans to add this size to its offerings once the carton becomes available. 

Two complete packaging lines

Each one of the Tetra Pak R2 filling machines heads up its own complete packaging line equipped with inspection systems, retort chambers, and secondary packaging equipment. Both of the R2 machines run all of the carton sizes. Changeover takes just minutes between the Midi sizes, as they all offer the same base dimension, with different heights. The 200-mL size has a different base, so changeover to that size can take from four to six hours, a process that is often done by NaturPak on the weekends.

Each R2 is fed by three small-batch kettles, with each one holding 1,000 lb of product. Tetra Pak supplies the converted carton blanks, which are supplied flat and are opened, filled, and sealed within the machine. The R2 offers three filling options: a packet filler, which can fill the carton with a single ingredient, a piston filler (two filling heads) for the main ingredient, and a filler that can top off a product with broth. Before exiting the machine, the cartons are sealed through a combination of heat and pressure.

The cartons then travel on a conveyor through a Mettler-Toledo in-line checkweigher that ensures the correct amount of product is contained within the package and then through a Tetra Pak-supplied inkjet printer that prints the best-by date, batch number, and lot code on the top of the carton. It next travels through a Novus X-ray system from JBT Corp. that inspects for foreign objects within the product. Every 15 minutes, an operator on the line pulls a product and performs a quality check. 

NaturPak operates six Surdry retort chambers—three for each line—that cook and sterilize the pet food products in-pack.NaturPak operates six Surdry retort chambers—three for each line—that cook and sterilize the pet food products in-pack.The next step is in-pack cooking and sterilization via the retort process. For this, the cartons continue their journey on the conveyor until they reach an automated basket loading system from Jorgensen Engineering A/S, supplied by Tetra Pak. The system loads the cartons into the retort basket by rows, with each basket, or rack, holding 1,300 cartons. Once the basket is full, it’s manually rolled to the infeed of the retort system. Each packaging line feeds three retort chambers from Surdry, each of which holds 7,700 cartons.

Products are held in the retort chamber for a specific time period at a particular temperature, depending on the requirements of the recipe. Once the product is properly cooked and sterilized, the racks are then rolled—again manually—to another Jorgensen system that unloads the cartons in the same manner as they were loaded.

From there, the cartons are conveyed in single file to a Tetra Pak Cardboard Packer, which Marciniak says was chosen for its flexibility. NaturPak can provide customers with trays and wraparound cases in formats that range from six-packs all the way to 28 units/case. A DT Industries Kalish Packaging Systems shrink bundler wraps multipack trays, which are then conveyed through a shrink tunnel.


   Read how co-packer River Run Foods expanded its capabilities with retort cartons.


For the final step, finished trays and cases are palletized using either an in-house designed palletizer or one supplied by Tetra Pak (depending on the packaging line), and pallets are then stretch-wrapped. Marciniak shares that NaturPak is awaiting the installation of a new robotic palletizing system from Fanuc.  

Before being released for distribution, finished products are held by NaturPak for two weeks, at which time a third-party lab tests the product to ensure there are no “microbial survivors.” 

Natural, wet pet food is the future

NaturPak is bullish on the future of its premium and super-premium wet pet food business. As mentioned, before the year is out, it plans to add another Tetra Pak R2 filling machine, at a cost of $6 million, and is contemplating adding more lines in 2022.

 Says Marciniak, “I’m not surprised by the growth, but I would like it to grow faster. I’m more surprised that customers aren’t aware of how good these products are for their pets, as well as the benefits of the packaging for their environment. That’s part of the education that must happen—educating them on the quality of minimally processed wet pet food. 

“Working for the Tetra Recart platform has given me a huge advantage in understanding the technology and moving in the right direction. So, in recent years, my focus is more on the ingredients and final product, because the packaging is perfect!”  

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