The year 2003 has not been the time for revolution in plastic or its rapidly growing sector of bottles and, not incidentally, their wide-mouth version, jars.
Much has been researched, written (including in this column), and spoken on the crucial topic of barrier properties of plastics and technologies to enhance them. And much has been discussed on interaction of plastic with beverage and food contents, and on the differences between cold, hot, sterile, aseptic, and extended-shelf-life (ESL) filling. But, as professionals roam the aisles of monumental packaging exhibitions, the largest and most spectacular displays are machines—those enormous electromechanical engineering marvels that marry product with the plastic bottles and that increasingly also make the plastic bottles before or during the packaging process.
2003 was not the time during which the first of the integrated bottle making/ packaging systems were developed and installed. Rather, today is a good time to stop and try to enumerate and assess the offerings from the perspectives of food scientists, technologists, and packaging engineers.
Hardly a woman is now alive who recalls the squeezable Stopette deodorant bottle, the 1950s initiation of plastic bottle packaging. Few are old enough to remember the struggle to introduce extrusion-blow-molded, high-density-polyethylene bottles for milk as a competitor to glass bottles (yes, Virginia, milk was formerly packaged in glass) and gable-top polyethylene-coated paperboard cartons.
One telling argument was that paperboard cartons were delivered flat to be erected in line with the filling operations, thus reducing space volume. Plastic bottles occupied large volumes and required shipment of air to reach the dairies. Glass bottles were reusable and so did not suffer from the volume hurdle, even when being returned from the consumer, a one-to-one substitution. The solution: make the plastic bottles in or next door (through the wall) to the dairy. And back then, food company manufacture of package structures was hardly unique—doesn’t everyone remember when 40% of food cans were made by the food companies?
And so, despite its infant technology, plastic bottle extrusion-blow-molding machines plus adjunct plastic-resin silos were installed in dairies around the country, in- or off-line with milk fillers. The links with blow-molding equipment and bottle makers were strong because dairies needed their expertise to ensure that the continuous flow of bottles contained the ceaseless outputs of the cows. Bottle suppliers such as Consolidated Container (née Continental Can) installed and still operate the equipment, even though the process is so technologically advanced that little human intervention is required—an essential in beverage plants.
The 1970s/’80s development of polyester bottles for carbonated beverages and their subsequent penetration into many other applications (think peanut butter, juice, isotonic drinks, water, salad dressings, etc.) necessitated a different thought process. Polyester required a preform-injection-molding process prior to careful reheating and stretch blowing, a sequence much more complex than extrusion of a polyethylene parison followed by blowing. For years, despite a few ventures into one-step fabrication, most polyester bottles were manufactured off-site by a two-step process (inject/reheat blow) and delivered to packaging operations, despite the space volume issues. But as bottle makers climbed the polyester-bottle learning curve, notions of in-line and on-site polyester bottle making re-emerged.
Even as more complicating variables such as heat setting (to accept hot filling) and multilayer structures (to enhance barrier, even with extrusion-blow-molded bottles) influenced the processes, mono-layer polyester bottle making equipment was being installed near food and beverage packaging operations. Mostly, specialized injection molders made preforms and shipped them to packagers who stretch blow molded them into bottles and conveyed them to adjacent packaging lines, often at surprisingly high speeds.
Today, almost all large output packagers have installed capacity for polyester bottle making, either from purchased preforms or directly from resin into their own injection molding machines. Suppliers such as Husky for injection molding machines and Sidel for stretch blow molding equipment have led a successful transition for the large-unit-volume users and are targeting the smaller companies.
Integrated Systems for HDPE and Polyester
In 2003, two plastics are dominant for bottle making: high-density polyethylene and polyester, with variants being multilayer and coated and now incorporating active adjuncts such as oxygen scavengers. Hardly uncommon are in- or off- line bottle making, for economic and efficiency reasons. But intruding into the scene are systems in which the bottle making is even further integrated, upstream with resin and downstream with bottling. And both are increasingly connected with aseptic and ultraclean operations for sterile or refrigerated ESL beverage contents.
In my view, the integrated systems may be classified by three methods:
1. Level of Microbiological Load. Aseptic is used to deliver sterile beverage product. Today, this is usually high acid, since the technologies for low acid are not quite ready for commercialization under United States regulations. ESL is used to deliver a packaged beverage product with significantly reduced spoilage microbiological count to permit refrigerated distribution of in the range of 50–100 days.
2. Plastic Material. Polyester, even if shrouded by a printed full-body label, is transparent and tough, offering some oxygen barrier. HDPE is translucent and relatively easy to fabricate, and the scrap can be internally recycled, but it does not provide as much oxygen barrier as polyester.
3. Bottle Structure Origin. With plastic resin, the entire structure is fabricated from a base material within the system. With preforms, a preformed polyester structure is injection molded off-premises and production is completed at or adjacent to the packaging line.
These categories do not yet embrace the notion that more than one concept may be combined into a single system. Or that inclusion in this narrative does not preclude the fact that some plastic paperboard and flexible material packages are also contenders in this emergent series.
• From Resin to Filled Bottle. Perhaps the most advanced of the systems is blow mold/fill/seal, which starts with thermoplastic resin pellets that are melted at usually microbicidal temperatures to produce an extrudate forced through dies. The oldest and evidently most reliable is from Germany’s Rommelag, which produces Bottlepack® blow mold/fill/seal equipment in which the heat of the melt sterilizes the bottle interior. All of Rommelag’s equipment is for monolayer extrusion blow molding of HDPE bottles, for products such as pharmaceuticals and fruit-flavored beverages. The resulting bottles are onetime opening because the closure is unitary with the bottle body, i.e., there is no reclosure. Such systems limit the flexibility and output of the packager: mold sizes and shapes are essentially fixed. And questions are posed as to the ability of dry-resin-melting heat to destroy thermally resistant pathogenic microorganisms.
Another system is injection blow mold/fill/seal. Polyester resin is now being fabricated into test tube–shaped preforms for downstream blowing and filling on a single closed line. Italy’s SIPA has engineered such a system, which involves transfer under positive pressure of sterile air of the preforms within the closed area from injection molder exit to stretch blow molding and subsequently to the Italian Procomac aseptic bottle filling machine, all within a confined space. The system, capable of an output of up to 600 bottles/min, is largely employed in Italy for ambient-temperature shelf-stable high-acid beverages.
The integrated SIPA/Procomac system obviates the need to sterilize bottles after fabrication, and theoretically reduces costs since no intermediaries are involved. On the other hand, any transient flaw anywhere in the system translates throughout and results in the entire system being down. Furthermore, output is governed by the least-efficient or slowest element. And, of course, the capital investment in a unitary system for a packager is relatively high.
• From Preform HDPE to Filled Bottle. Netherland’s Stork system represents a variation on the direct resin-to-filled bottle approach. Beginning with HDPE resin, the system extrudes and blows a closed monolayer bottle whose interior is sterile by virtue of the extrusion temperature. In a sterile environment, the closed orifice is sliced off (and returned to resin for recycling), leaving an open-top bottle. The bottle is then treated with hydrogen peroxide to sterilize both interior and exterior. Under aseptic conditions, the bottle is transferred for aseptic filling—commercially for low-acid beverages such as coffee distributed under refrigerated ESL conditions.
Switzerland’s Elopak, in conjunction with extrusion-blow-molding equipment maker Techne, now offers a range of HDPE bottle systems for refrigerated ESL beverages. Resin is converted into closed-mouth, sterile-interior bottles that are transferred under sterile conditions (for the interiors only, since the exteriors are exposed) to the Elopak aseptic filling machine. In this equipment, the flashing seals are cut off, exposing the sterile interiors for filling and sealing with pre-sterilized closures.
• From Preform Polyester to Filled Bottle. Tetra Pak’s French Sidel and its filling-machine cousin company Remy have combined for an analogous system. Sidel equipment forms the polyester bottles from preforms that are sterilized with hydrogen peroxide prior to blowing with sterile air. The preforms are transferred under aseptic conditions to the Remy filler. No bottle sterilization is required between bottle blowing and filling, as the filler has been pre-sterilized and maintained sterile in a Class 100 clean room.
These systems are commercially employed to produce refrigerated ESL lowacid beverages (ultra-clean)—although, as the supplier correctly points out, it is applicable for sterile ambient-temperature shelf-stable high-acid beverages (aseptic) and for refrigerated ESL highacid beverages (clean). Bottle output can be 100–600 bottles/min. Advantages of the preform-to-filled-bottle systems are total control, less total equipment, and no bottle storage. System efficiency, according to the maker, is 90 %.
Transcending the Traditional
And then there are the systems that suggest their superior microbiological safety because they begin with preformed plastic bottles and treat them with hydrogen peroxide, peracetic acid, ultraviolet radiation, or combinations prior to filling in Class x00 rooms. Krones (Germany), Remy (sans Sidel), Sasib (Italy), Shibuya Kogyo (Japan), Bosch (Germany), EPSI (U.S.), Tetra Pak (Sweden), KHS (Germany), Ave, Elopak, and probably others all offer the basic rotary (or linear) clean and aseptic fill/close machinery. That they have all installed functioning equipment means that when the conservative refrigerated ESL technology is employed the systems appear to be microbiologically sound.
The core value of this brief is that more than a dozen solid organizations have engineered and built commercial equipment to effectively fill HDPE, polyester,and multilayer barrier versions either aseptically or under clean or ultraclean conditions. The result is the ability by beverage processors to package products capable of prolonged quality retention during controlled distribution. And some of these suppliers have stretched the technology by integrating the filling with plastic bottle making. Form/fill/seal for barrier and non-barrier plastic bottles under microbiologically controlled conditions represents an exciting new direction for beverage processors.
The emergent universe of ESL beverages has exploded in the food market with quality products that have delighted consumers and is thus changing the face of the beverage system. That the packaging equipment for delivering these products has leaped upstream and downstream so boldly is a tribute to the chutzpah of the engineers who have transcended the traditional to succeed in blending microbiology, biochemistry, and packaging into consumer products.
by AARON L. BRODY
President and CEO, Packaging/Brody, Inc.