Packaging under pressure

by Kimberlie Clyma
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igh-pressure pasteurization (HPP) is not a new technology to meat and poultry processors, but it’s not exactly mainstream either. The process of denaturing pathogens using up to 87,000 pounds of water pressure is being used by an increasing number of processors including Tyson, Perdue Farms, Hormel, Oscar Mayer and most recently, Cargill. The technology is an effective post-packaging intervention, however, the added equipment expense, challenges with existing product packaging and obstacles related to implementing it as part of automated operations is hindering universal adoption of HPP throughout the industry.

HPP technology can be used on a variety of meat products, seafood, ready-to-eat meals, vegetables, sauces and marinades, fruits and juices and dairy products. The goal of treating the foods with HPP is to reduce or eliminate pathogens to extend shelf life and enhance food safety. Pathogens such as E. coli, Salmonella and Listeria can be virtually eliminated using this method.

Though specific systems vary slightly, this is how the process works in general: Packaged food products are placed in a cylindrical pressure vessel; water is added to the vessel and then the contents are pressurized at levels up to 87,000 psi; once the required pressure is achieved, product is held at that pressure for a predetermined dwell time – typically three minutes. The intense pressure interrupts the cellular activities of foodborne pathogens and other microorganisms, and they die. The pressure in the vessel is known as hydrostatic pressure, which means it is applied equally in all directions, ensuring the product will not be crushed while in the vessel.

After the vessel is pressurized for the required amount of time, it is decompressed and the product can be removed from the vessel. The treated food packages then go through a drying process before being sent to the final packaging area for label application, boxing and shipping.

Commercial viability
The benefits of HPP technology when it comes to extending shelf-life and enhancing food safety are virtually undisputed. Experts including Dr. James Marsden, senior science advisor of the North American Meat Processors Association and the Regent’s Distinguished Professor of Meat Science at Kansas State Univ., have worked with the technology to conduct studies to verify its effectiveness.

“HPP for processed meats works beautifully, it’s well proven and established in the marketplace,” Marsden says. “It takes Listeria right off the table. It virtually eliminates the risk of Listeria in those types of products.”

HPP is also highly effective with other types of meats. Marsden conducted a study at KSU, in conjunction with researchers at the Univ. of Nebraska, to fi nd out if HPP is as effective in killing Salmonella and E. coli O157:H7. “We conducted an inoculation study and then measured the reduction of Salmonella and E.coli O157:H7 with HPP treatment,” he continues. “We got a 5-log reduction for both pathogens, which is the same result as cooking. It virtually eliminated E. coli and Salmonella from raw ground beef.

“That said, even though it works great from a food safety point of view, there’s a lot that has to be done to make it commercially viable. HPP can distort the appearance of the product, it can change the color of the product, and sometimes it can create heat,” Marsden adds. “Temperature has to be controlled during the process. Packaging has to be well designed so that it doesn’t get distorted. And oxygen has to be controlled so that you don’t get oxidation or browning of the product during treatment.

“But if all these parameters are controlled, then it can work beautifully for any type of product,” he says. “I can remember having the same conversation about HPP 10 to 12 years ago when processors first wanted to start using the technology on processed meats, and the same challenges and concerns were out there. Obviously processors were able to overcome the obstacles. I have no doubt that they will be able to overcome the same challenges for raw meats.”

Perfect packaging
Packaging concerns top the list when it comes to processors considering adding HPP to an existing production system. “Not all packaging is suitable for high-pressure processing,” says Greg Zaja, vice president of sales and R&D for Milwaukee-based American Pasteurization Company, where food companies ship their products to be HPP treated. A growing number of meat and poultry processors are utilizing APC’s service, and depending on the type of products, packaging is a consideration. “More and more packaging suppliers are adapting to the technology and understand the physical properties that are necessary for packaging materials that are high-pressure processed.”

According to Avure Technologies Inc., some of the potential packaging roadblocks include an excessive amount of packaging “skirt” material, which can limit the effi cient utilization of the high-pressure cylinder; the amount of gas flushing in a package; and the seal ability of the flexible packaging material.

“When new products are introduced to HPP there are concerns that the product packaging will not withstand the process due to the film properties or package fl exibility,” Zaja says. “Changes are typically made to the packaging materials to ensure all parameters are suitable for a specific product by using HPP.”

It’s not enough to simply provide the HPP equipment to processors, many HPP technology companies fi nd it necessary and valuable to work closely with packaging companies to make sure the technology and packaging work together in the most effi cient way. “Packaging companies we work with are prepared to work directly with their customers to make whatever packaging changes are necessary in order to incorporate our technology,” Zaja says.

Avure works with major flexible fi lm producers to design solutions for its customers’ applications. “In addition, the Avure HPP lab in Kent, Wash., possesses signifi cant knowledge of packaging and work directly with our customer base to address any issues that they might face during the HPP adoption process,” says Matt Rutherford, senior vice president of global sales for Avure.

Kansas City, Mo.-based Multivac Inc. has gone a step further and created a partnership with Uhde High Pressure Technologies to offer its customers a one-stop-shop for HPP and packaging technology. The German company has more than 80 years of experience in high-pressure applications.

One challenge of adding an HPP step to a processing operation is integrating it into an otherwise fully automated facility. The loading and unloading of the high-pressure vessels is typically done manually in order to maximize the amount of product that fi ts into the vessel.

“We try to fi nd a balance between automating the technology and achieving the most fi lling ratio in the vessel,” says Jaime Nicolas-Correa, commercial manager for NC Hyperbaric, a Madrid, Spain-based supplier of HPP equipment. “We can automate the loading and unloading process of the product into the HPP containers but the filling ratio will be lower than if it’s done by hand and the production per hour will also be lower. This isn’t always cost effective for the processor.”

Not unlike APC, Safe Pac Pasteurization recently began offering HPP technology from NC Hyperbaric to processors of food products on a contract basis from its East Coast facility.

Integrating solutions
Keeping costs down and maintaining production effi ciencies are constant concerns when considering the addition of new technology such as HPP. Multivac, as a market leader in thermoform packaging machines, is successfully overcoming this obstacle. The company recently announced its newest technical innovation that allows its HPP technology to be integrated into fully automated packaging lines. Prior to this innovation, HPP was typically conducted in a separate manufacturing stage, which some processors consider to be disruptive to throughput. Using patent-pending technology, Multivac has developed a solution to integrate high-pressure equipment into packaged food lines, according to Tobias Richter, product manager in the Systems Business Group for MULTIVAC Sepp Haggenmüller GmbH. The solution includes the high-pressure equipment as well as an automation concept to integrate the process into packaging lines designed to meet the demands of the food industry.

With the integration solution developed by Multivac, the finished food packages are automatically loaded into transport containers, HPP-treated, and then automatically unloaded before being dried and undergoing necessary labeling and packed into cartons. “In this way, it is for the first time that we can process large, industrial-scale production quantities fully automatically in a quasi-continuous operation,” Richter says.

Efficient use of the space inside the HPP vessel is crucial to achieving maximum productivity, Richter says. “Since the high-pressure equipment is round for reasons of optimizing the distribution of pressure forces, the loading pattern also has to be designed accordingly.” With a favorable pack shape it is possible to treat up to four tons of packaged food per
hour in the high-pressure equipment.

Multivac engineers work with customers to develop the optimum package shape and a customer testing facility is available at its Uhde High Pressure Technologies offi ce in Hagen, Germany.

Multivac also offers a high pressure compatible packaging concept for modifi ed-atmosphere packaging applications.

“There are challenges with MAP packages since they are more rigid and the amount of gas in the package makes it more expensive per pound to treat. But if our customers insist upon MAP packages, then we can fi nd a way to work within those parameters,” Nicolas-Correa says. “But with HPP, we don’t feel MAP packages are as necessary. The HPP technology eliminates the shelf-life issues that MAP packages were designed to deal with.”

Consumer acceptance
Unlike other food-safety or food preservation methods typically used on meat like irradiation, thermal treatments or chemical preservatives, high-pressure processing is in the unique position of having consumer support. Because the method is environmentally friendly and doesn’t require any product additives, processors can deliver the “clean labels” consumers are demanding.

“There’s no consumer resistance to this technology. It’s unlike any other process out there,” Marsden says.

The positive consumer response to HPP technology is helping to raise industry awareness and acceptance of the technology as a viable food preservation and food safety technique. “High pressure provides many added values to processors such as extending shelflife, which results in better managing of raw materials, fewer changeovers, reduction of the cost of returns and the expansion of distribution areas,” Zaja says. “Consumers can finally enjoy safe, quality products without preservatives. More manufacturers are advertising this process [HPP] directly on their labels to let consumers know they have taken extra hurdles to provide them with quality, safe products.”

“We have just begun to tap into the potential created by this exciting technology,” Rutherford says.
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