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Aseptic filling sans sterilants

When a Colombian beverage marketer became the first to produce a packaged version of the popular Avena drink, the company used aseptic technology that was simple and secure.
If New Yorkers take a liking to Avena a milk-and-oats-based beverage that will be introduced in the Big Apple this fall they'll have aseptic packaging technology to thank.

The unusual drink hails from Colombia where it's been a favorite of young and old alike for generations. Until recently however it was never available prepackaged. Made in the home or in small shops it has always been served fresh and refrigerated.

Alpina Productos Alimenticios a beverage marketer based in suburban Bogota changed all that in 1994. That's when it introduced Avena in thermoformed cups filled aseptically on a Neutral Aseptic System (NAS®) from Erca Formseal a French machinery manufacturer represented in North America by Autoprod (Clearwater FL). The 250-g cups of Avena have proven so popular in Colombia and Venezuela that Alpina is about to install a second NAS aseptic system that will permit it to explore additional export opportunities including New York.

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Available since the mid-'80s Erca's NAS machines are called "neutral" because they employ no chemical sterilants such as hydrogen peroxide or oxonia. Instead the inside of the cup is essentially sterilized when the sheet is coextruded. In the Formseal system the top layer is peeled off exposing a sterile layer below. According to Alpina vice president of operations German Tellez Diaz the simplicity and security of an aseptic system that does not require treatment with and removal of chemical sterilants were the two factors that made the NAS system so appealing compared to other aseptic technologies.

The forming web is a four-layer coextrusion of polystyrene/ethylene vinyl alcohol/polyethylene/polypropylene. The PE becomes the food-contact layer and its sterility is assured because of the high temperatures during coextrusion. The function of the PP layer that covers the PE is to keep the PE sterile indefinitely.

In the Erca NAS machine the PP is removed to expose the sterile PE surface. The PP layer is automatically wound and in Alpina's case discarded because there is no market for recycled PP in Colombia.

Preventing recontamination

Recontamination of the sterile PE surface is prevented because the instant it's exposed it enters a sterile chamber that's overpressured with sterile air. In this chamber the material is thermoformed filled and lidded.

Lidding material also has a peelable PP layer that is removed within the sterile chamber. Supplied by VAW Europack (Bonn Germany) the alsa-up® lidding material has another interesting feature: When the consumer peels off the lid a thin layer of polyester remains behind. Punched into it is a hole through which the liquid product can be drunk straight from the cup or poured easily into a glass.

The lidding provided to Alpina is a three-layer lamination of PP/polyester/foil. The foil is lacquered and then gravure-printed in five colors.

The polyester layer has the drinking holes perforated into it before it's laminated to the foil. When the consumer peels the foil layer from the cup the scored drinking hole sticks to the foil. Thus it's removed while the rest of the polyester remains sealed to the rim of the cup.

Thermoforming on the Erca machine is done six-across and two in the machine direction. The machine cycles 23 times/min to produce 276 cups/min.

Full-wrap labels are applied in-mold. The alsawax® label also from VAW Europack consists of two layers: paper and a hot melt sealant coating that is applied to the paper by cylinder much like a gravure press applies ink to a substrate.

The label material unwinds from its roll and is immediately cut into 12 strips each strip leading to one of the 12 thermoforming cavities. As the sheet is thermoformed into each mold the heat activates the hot melt causing the label to bond firmly to the sidewalls of the newly formed cup.

According to Frederico Hincapi packaging analyst at Alpina shelf life is four months at room temperature. "But we have underway a study to see if we can reach six months with the same technology and the same packaging materials" he says. The lid of each cup is ink-jet-printed with a best-if-used-by date.

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