Marketing mussels with a microwave boost
Fresh mussels have a short shelf life and aren’t easy to prepare at home. Microwave pasteurization addresses these issues and provides a 21-day refrigerated shelf life. Dutch seafood marketer Roem van Yerseke is using microwave pasteurization technology to launch a line of refrigerated ready meals consisting of mussels, vegetables, and seasonings. The taste of the meal, says the firm, is comparable to the taste of fresh mussels prepared in the traditional way: steamed. But the advantage to consumers is that the 750-g serving can be prepared in the home microwave oven in less than 5.5 minutes.
Fresh mussels have a short shelf life and aren’t easy to prepare at home. Microwave pasteurization addresses these issues and provides a 21-day refrigerated shelf life.
The technology behind the launch is called MicroPast, which was developed by Creative New Food GmbH. The process engineering partner is International Packaging Systems, a part of Germany’s Schubert Group.
Micropast is essentially a variety of steam pressure cooking in which microwaves function as the source of energy. Because throughput time is in the range of 8 to 12 minutes instead of two to three hours for pasteurization in a steam oven or autoclave retort, MicroPast puts less thermal stress on the food. This leads to increased nutritional value, more attractive color retention, and better food taste and texture. In addition, raw menu components such as vegetables, fruits, and chicken/pork/fish are cooked in one step. There’s no need for pre-cooking operations, so overall prep time is greatly reduced. And finally, energy consumption is minimal.
Live mussels
Below the overhead scale, thermoformed polypropylene trays are automatically denested in a single file and conveyed beneath the depositing funnel that drops the mussels. A short distance later, vegetables are deposited from the same overhead scale. A separate depositor then adds a water solution with seasonings. No preservatives are involved.
Next is heat sealing of the clear lidding material, performed on a machine that does four trays per cycle and cycles 10 times per minute, so typical throughput is about 40 trays/min. Roem van Yerseke chooses not to identify tray material or lidstock, and the firm is equally guarded about machinery vendors.
Lidding material includes small punctures done in registration as well as eye marks that can be read by the lidding machine. The end result is that the lidding material applied in registration to each tray has a steam-pressure release hole through which steam can be released as the trays make their way through the microwave pasteurization tunnel. Without this release valve, pressure would build inside to the point where the lidding would burst apart from the tray. An interesting detail: The circumference of each of these punctures is reinforced with a bead so that it can withstand the process stress inside the microwave pasteurization tunnel without tearing and permitting more venting than the design spec calls for.
As trays exit the lidding machine, they pass over a checkweigher. “It’s critical that the amount of product in each tray is within acceptable parameters because the microwave pasteurization process is very precise and depends on having the right amount of mussels in every single tray,” says Johan Lacor, manager of the seafood division at Roem van Yerseke. Should any tray be over or underweight, the checkweigher catches it and causes that tray to be ejected from the line.
Trays make a right-angle turn and are metered into a collating device just ahead of the entrance to the microwave pasteurization unit, manufactured to International Packaging Systems’ specs by a German manufacturer. When six trays are in place, the collator pushes all six at a right angle into the pasteurizer, which means they travel six-across.
As the food products are heated by the microwave energy, steam is produced inside the tray. Because steam is an optimal heat conductor, no hot or cold spots are created, and high core temperatures between 90 and 95 deg C are generated inside the product in a short time.
Cooling bath
Surface temperature of the food inside the pack drops by 10 to 15 deg C. This prevents the generation of a vacuum during cooling. The six trays now index forward to a station in which both openings—the steam-pressure release hole and the small puncture created by the MAP system for injection of the nitrogen—are closed by a special label to maintain the sterile environment inside the pack. This MicroPast label plays another important role when the consumer heats up the ready meal in the microwave oven. The label is a one-way valve that lets steam and pressure vent from the container so that the tray won’t burst.
Trays exiting the MicroPast label application station pass through a metal detector and then an ink-jet printer that puts product name and a lot number useful only to Roem van Yerseke. The final piece of equipment in the line is a spiral cooler that brings temperature down even further. Consumer-facing information like best-use-by date is imprinted on a paperboard sleeve that is subsequently applied by hand.
Marketed under the Zeeland’s Roem a la minute brand, these ready meals began reaching store shelves in the Netherlands, France, Belgium, and Germany in June. Selling price is about $6.00 for the 750-g serving.
Distribution is through a local distribution company. “We have more than 30 years experience in the distribution of mussels because we go to market through the same distributors with our fresh mussels, too,” says Lacor. “With this new product we go to retailers, supermarkets, some restaurants and cafes. Small restaurants and cafes have a difficult time getting permits to prepare fresh food. This product is easier for them to serve their customers because in fact the café need only re-heat these meals, not cook them from raw ingredients.”
When asked if being among the first to commercialize such cutting-edge technology was at all unnerving, Lacor acknowledged that it wasn’t without risk. “But we had and continue to have confidence in IPS, and in fact everything is running extremely well.”