Aseptic vs Hot-Fill Packaging for Polyester Bottles

Who can figure it? Polyethylene terephthalate (PET) polyester bottles for beverages and other liquid foods continue to penetrate the food packaging scene.

Whatever happened to coextruded polypropylene/ethylene vinyl alcohol (EVOH) barrier bottles and jars? (They are still out there if you look past the bizarre high-density polyethylene, HDPE, and “other” plastic classifications on the bases of food and beverage packages. And what of the potential for polypropylene (with barrier added) for hot filling? (Look at the new baby juice initiative.) And when are we to witness polyethylene naphthalate (PEN)—a newer and more heat-resistant polyester that provides a better oxygen barrier than PET—and all those other interesting polymers that have generated packaging headlines for many years?

PET—the “1” in the triangle/PETE on your plastic bottle base—still leads in “barrier” packaging, although if you examine it carefully, you might find a bit of marriage with EVOH or oxygen scavenger.

Thrust upon us in 1977 when the Food and Drug Administration banned polyacrylonitrile for packaging, polyester did not and does not possess the gas or water vapor barrier properties or thermal resistance to permit its naked use for containment of most food or beverage products sensitive to oxygen or loss of carbon dioxide or water gain or loss. And PET is not the easiest of polymers to fabricate or to marry to other functional polymers. But there it stands, by far the leader—as consumers continue to demand clear, tough plastic for their food and beverage packaging. So product quality is moderately compromised and distribution systems shortened to accommodate to the protection requirements and consumers.

At the forefront of polyester bottle and jar packaging today is beer. Converting beer packaging from glass and aluminum in the U.S. has been a major objective of plastic suppliers for decades. The first of the realistic commercial polyester beer bottles appeared in North America in 1999, but they were and are not solely polyester. Complementing the polymer are such materials as scavengers, either layered or in the mass, to intercept oxygen from the air and help retard biochemical changes in the product during distribution. But polyester’s relatively limited temperature resistance, coupled with the fact that most American beer is thermally pasteurized before distribution, has led to the application only for cold-filled or “draft” beers. In effect, only beer that is “aseptically” packaged is currently in polyester bottles. Polyester cannot withstand the rigors of post-fill thermal pasteurization.

But announced in recent months have been “pasteurizable” polyester bottles, incredibly introduced in, of all places, China. U.S. equipment technology developer Kortec and Zhong Fu Industries of Zuhai, China, have coinjected a core barrier with polyester in a new structure claimed to be capable of resisting temperatures of 153°F for 20 min. The core layer may be either Dareval EVOH/oxygen scavenger or Honeywell’s nylon/nanocomposite/oxygen scavenger, both of which are engineered to retard both oxygen entry and carbon dioxide loss—a dual property not as available from oxygen scavengers alone.

According to“Aseptic vs. Hot Fill for PET: Comparative Costs, Other Drivers & Projected Unit Volumes Through 2004”—a 2001 multi-client report published by Packaging Strategies, West Chester, Pa.—the major products that are considered as candidates for either aseptic or hot filling into polyester bottles are juices and juice drinks, isotonics, ready-to-drink teas, and dairy-based beverages such as chocolate-flavored milk.

Unit volume of PET to contain multi-serve juice and juice drinks is about 1.8 billion, including a few still in metal cans (remember those 46-oz steel cans?) and glass bottles. In the single-serve juice and juice drink category, about 1.3 billion units are expected to be produced in 2001, with aseptic composite paperboard leading, followed by hot-fill standup flexible pouches, glass bottles, and metal cans. Polyester is last, but expected to grow to the number-one position within two years.

Nearly 3 billion polyester bottles of isotonic beverages will be produced in 2001, with both glass and metal almost gone from this category.

About 1.4 billion units of ready-to-drink tea will be produced in 2001, with two-piece aluminum cans dominating, followed by glass bottles. A not-inconsiderable fraction of ready-to-drink teas is cold filled, meaning the incorporation of chemical preservatives.

Almost all of the volume in dairy-based beverages is for extended-shelf-life (ESL) rather than ambient-temperature shelf-stable aseptically packaged. Most today is in HDPE, with polyester growing as a structural material.

Issues in considering the choice between hot fill and aseptic packaging for the four beverages discussed include:
• The heavier mass of PET bottle required for hot filling to withstand the heat.

• The heat-setting process that is required to approach the 180°F of hot filling for high-acid beverages, slowing the PET bottle fabrication.

• The cost of obviously more expensive aseptic packaging equipment—about $ 10 million for aseptic vs half that for hot fill, even including the massive cooling tunnels.

• Significantly slower operating speeds for aseptic vs hot filling.

• Greater operator skill requirements for aseptic vs hot filling.

• Usually better quality of aseptically packaged vs hot-filled beverages.

Time for heat setting the plastic costs the bottle maker about 2% of total costs of about $0.07 per 16-oz bottle. Beyond the plastic mass difference, which is about 20%, is the need to incorporate collapsing panels into the bottle structure to accommodate to the internal vacuum generated from cooling. Not included in the computations in the report are the potential changes in shelf life because of the differences in wall thickness between aseptically packaged and hot-filled beverages. All of the high-acid products being considered are susceptible to oxidative changes with time at ambient temperatures. ESL dairy-based beverages that are distributed under short-shelf-life refrigerated conditions do not undergo as many measurable changes.

Combining the cost data indicates that, from a variable cost perspective, hot filling is more expensive than aseptic filling. The difference is about $0.006 per bottle in favor of aseptic—on a total packaging cost of about $0.10 for 16-oz polyester bottles.

In 2000, aseptic packaging in polyester bottles represented approximately 10% of all packaging for juices, juice drinks, and ready-to-drink tea. This proportion is expected to leap to 18% in 2001 and nearly 30% by 2004, according to the report. The greatest growth for hot fill will be in single-serve juices and juice drinks because the barrier of PET is not yet sufficient for the higher surface-to-volume ratio of small bottles. The greatest growth in aseptic is projected to be in isotonic beverages, where aseptic packaging is being introduced for the 24-oz size, the major growth sector.

But, and this is amazing, the installed capacity for aseptic packaging into PET (or analogous) bottles is only 2.4 billion units, more than double that projected to be produced for 2001 but only half of what is predicted to be required in 2004. I count seven manufacturers having commercial aseptic bottling equipment in the U.S. and another 20+ offering such equipment around the world. If the projections are correct, and I believe that they are conservative, a very exciting competitive battle to capture aseptic bottling market share in this country has commenced.

What an interesting turn for a technology (aseptic) that many had written off as archaic and for a package (polyester) that does not meet the barrier demands of its contents!

PRODUCTS & LITERATURE 
Horizontal Form/Fill/Seal Machine, the Pouch King 2000, processes up to 2,500 in of linear web per minute, while the continuous-motion filling system provides accurate pouch-to-pouch weight control. A common-socket flexible filling system uses simple slide-in change to enable a wide variety of product feeds. The machine features stainless-steel construction and low-pressure washdown capability. For more information, contact R.A. Jones & Co. Inc., P.O. Box 485, Cincinnati, OH 45201 (phone 859-344-7153, fax 859-341-0519, www.rajones.com) —or circle 317.

Closures for Standup Pouches are available in three versions: push-pull with overcap, and twist with overcap, and twist with tamper-evident band. The push-pull closure is the industry standard for beverages and has been adapted to dispense product from flexible pouches. The twist style allows the user to squeeze the pouch and dispense the contents in a controlled stream. For more information, contact Creative Packaging Corp., 700 Corporate Grove Dr., Buffalo Grove, IL 60089 (phone 847-808-7200, fax 847-215-0351, www.creativepkg.com) —or circle 318.

by AARON L. BRODY
Contributing Editor
Managing Director, Rubbright•Brody, Inc.
Duluth, Ga.