Barriers for success How technology keeps beer in PET fresh
By Dan Griffiths
The market for single-trip kegs has increased rapidly in recent times and the PET container has in many ways enabled this growth. But with supply chains increasing in length and complexity, there is an ever greater demand for packaging materials to maintain the freshness and quality of beer for longer. In this article, we will look at the quality issues that have affected PET containers in the past and how the use of innovative barrier mate- rials and construction techniques have given brewers the confidence to package more of their production into this material. History of PET as a beer container PET was first developed in the 1941 at the Calico Printers’ Association Ltd in Manchester, England, in the midst of the second world war. Originally intended for use as a synthetic fibre, the material was destined to find use in a wide range of industries and applications. The first PET bottle was patented in 1973 and rapidly found favour in the carbonated soft drinks market, becoming the container of choice by the early 1980’s. However, despite frequent predictions that the PET beer bottle was about to be- come ubiquitous, the use of PET in this capacity remained stalled, being confined for the most part, to certain high-volume applications. Sporting events, music venues and festivals found a use for PET due to its safety and handling benefits when compared to glass. PET also found a use as a container for alcoholic bever- ages at the lower end of the market, some of which are produced in larger
In addition to providing physical and microbiological protection, any material used for packing beer must have three basic barrier properties; it must prevent the ingress of O 2 , it must prevent the loss of CO 2 and it must provide adequate protection from UV light. On top of this, it must be able to do so without contributing any taints, or removing flavour from the product.
I n the modern era, glass and steel have long been used successfully as primary packaging materials in the beer industry. Glass bottles provide a nearly perfect barrier against gas transfer (issues surrounding clo- sures not withstanding), can be tinted to reduce UV light transmission and they present the product in a highly attractive format for the consumer. Steel kegs, which have the advantage of being highly durable, are likewise impervious to gas, and provide com-
plete protection against UV light. For small pack beer, the shelf- life is often considered to have been exceeded once the dissolved O 2 level has exceeded 1ppm. The imperfect seal formed by glass bottle closures results in an O 2 ingress of between 2.0 and 8.4ppb per day, and so a shelf life of between approximately four and 13 months (Bamforth and Krochta, 2010). Use of an O 2 scav- enging material in the closure can extend this period, to a degree. O 2 pickup by an up-tapped steel keg is much lower, but due to other quality concerns, a shelf life of 90 days is often given. The many advantages that the carbonated soft drinks industry have gained from the switch to polyethyl- ene terephthalate (PET) bottles have not gone unnoticed by brewers. PET containers are light and shatterproof, can be stretch-blown from preforms at the brewery, and offer a greater range of marketing opportunities. To- day there are many options available which provide the handling benefits of PET, while giving an excellent barrier performance.
A PET preform and the stretch blown kegs which are formed from it
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For a beer containing PET bottle, oxygen, being approximately 21% of dry air, and having a partial pressure of around 19.6kPa at sea level (ac- counting for the partial pressure of water vapour), O 2 will diffuse into the bottle at a much greater rate than the O 2 inside the bottle will be moving out of it. The partial pressure of CO 2 inside the bottle is, likewise, much higher than that outside of it, resulting in a net loss of CO 2 from the beer. There have also been issues in the past with the migration of flavour taints from acetaldehyde, which is used in the manufacture of PET and remains in the material in low concentrations. Health concerns over the use of antimony during the manufacture of PET would appear to be unfounded, with numerous studies showing that the trace amounts that remain in PET cannot raise the level present in the liquid above the WHO’s safe consumption level. Barrier materials To enable PET to be used successful- ly as a replacement for glass bottles and steel kegs, its barrier properties container wall that we observe a net change (this phenomenon can be ex- ploited to actively remove oxygen from packaged product, something we will return to later).
O 2 permeability 23C 0% RH [cm3.mm/m2.day.atm]
1-5 50-100 50-200 100-150
Polyethylene terephthalate (PET) Polypropylene (PP) Polyethylene (PE) Polystyrene (PS) Poly(vinyl chloride) (PVC) Poly(ethylene naphthalate) (PEN) Polyamide (PA) Poly(vinyl alcohol) (PVAL) Ethylene vinyl alcohol (EVOH) Poly(vinylidene chloride) (PVDC)
0.1-1 (dry) 0.02 (dry) 0.001-0.01(dry) 0.01-0.3 Figure 1: O 2 permeability of polymers commonly used in packaging (Lange and Wyser, 2003)
Figure 1 , the shelf-life of beer in an untreated PET bottle can be as short as three weeks, due to oxidation. The mechanism by which there is a net change in gas concentration across a permeable solid, such as PET, consists of three processes; the gas is absorbed at the material surface; it then diffuses through the material; and finally, it desorbs from the surface at the other side. The partial pressure of a gas on either side of the material will deter- mine the net direction of gas trans- port, as gaseous exchange proceeds towards equilibrium, in accordance with Henry’s law. An interesting point to note here is that the transport of gas occurs in both directions and it is only due to the great imbalance in concentrations on either side of the
formats (1 ltr plus), which are not practical in glass or can. The image problems that PET bot- tles, in particular, have suffered from may be partly due to this associa- tion with lower-quality products in the past. However, there is evidence that millennials (the generation born between 1982 and 2004) are increas- ingly less likely to make such a link and tend to view shatterproof ma- terials and re-sealable containers as benefits, rather than the sign of a sub-standard product. The wide- spread adoption of one-way kegs and cans in the craft brewing industry has also helped to raise awareness amongst consumers about packag- ing formats – and these have become discussion points around which social media campaigns are being based. It has not been until recently, however, that PET as a beer-packaging material has become more widespread. For while the physical properties of PET are sufficient by themselves for main- taining an acceptable level of quality in the carbonated soft drinks market, beer presents a trickier proposition. The beer problem Beer is, in many ways, a delicate product. It is highly susceptible to staling due to the formation of off flavours from even very low levels (>50ppb) of dissolved oxygen (DO) in package. It’s perceived flavour and mouthfeel can be altered drastically by changes to the carbonation level and exposure to UV light will cause the formation of off flavours through a reaction with hop derived iso- α -acids. Taints that are picked up from the packaging material are easily de- tected in delicately-flavoured styles, and the absorption of compounds from beer by the packaging material can dull its flavour profile. While the O 2 permeability of PET is much lower than some of the other polymers that one might be familiar with, shown in
The tortuous path barrier slows the rate of gas diffusion through a material
Active elements of a barrier react to fix O 2 with the material as it diffuses through it
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In addition to the barrier materials, it is also possible to incorporate active oxygen-scavenging components such as a cobalt salt, which catalyses a re- action that actively fixes oxygen within the PET material. Multi-layer The first successful PET bottles suit- able for beer were manufactured with multi-layer construction techniques, involving up to nine layers. Co-injection molding machines are used to produce the preforms, in which the barrier materials are formed as distinct layers within the PET structure. Multi-layer bottles have very good barrier proper- ties, often making use of EVOH as the O 2 protection layer. The multi-layer bottle ecosystem is well developed and is still the most widely used technology for O 2 -sensitive PET bottled products such as sauces, juices and beer. However, a weakness of the multi-layer design is that due to the way in which the co-injection molders make the preform, the neck and the base of the bottle cannot con- tain the barrier layers. Monolayers In this construction technique, the bar- rier material is incorporated directly into the PET during its manufacture. A pre-prepared blend may be used, from manufacturers such as Invista and M&G Chemicals, or the barrier components may be supplied sepa- rately as a concentrated ‘masterbatch’, which the container manufacturer then incorporates into their PET blend in the appropriate concentrations. To obtain a PET container with the desired properties suitable for beer, a manufacturer would select and add masterbatches for; an oxygen barrier;
a CO 2 barrier; an oxygen scavenger and UV protection pigment. Much of the difference between commercially-available PET mon- olayer containers is due to the variations in the type and quantity of masterbatch used, with the specific preparations being largely available to all. With a typical oxygen bar- rier masterbatch costing 10 times that of PET, it is not difficult to see why balancing the barrier proper- ties of the container to the shelf-life requirements of the customer, all at an attractive price, is important. Invista’s PolyShield® is a com- monly used resin with enhanced barrier properties, utilised in the construction of one-way monolayer PET kegs and bottles. Petanier’s petainerKeg TM , Dispack-Projects’ Do- lium® Keg and Lightweight Contain- ers UniKeg® all use this blend, in combination with a small percentage (usually 3-5%) of MDX6 and a UV pro- tection pigment. The exact formula- tions used, however, are not publicly available. Petainer works in co-operation with the equipment manufacturer KHS who provides specialised pack- aging lines for the kegs, and have the largest market share worldwide, at approximately 60%. Independent test- ing at VLB has confirmed Petanier’s shelf-life claims of a minimum nine months, with taste tests being unable to differentiate between beer stored in steel kegs and PET. O 2 ingress over six months is given as less than 200 ppb, with a 12% loss of CO 2 over the same period. The Dolium® Keg has at least a six-month shelf-life after filling, equivalent to the recommended time for a stainless steel keg. It also has
The co-injection process forming a multi-layer PET preform
have to be greatly enhanced. This is achieved by the use of additional materials, which by themselves would be too costly, or might not have the desired structural or aes- thetic qualities. The type of barrier material used goes hand-in-hand with the construc- tion technique, of which there are three main types; a monolayer, in which the barriers are incorporated into the PET material itself; a layered construction, whereby the barrier material is sandwiched between struc- tural PET components; and thin film coatings, that are applied to the inner or outer surfaces. A fourth method of tackling the issue is through the use of an inner bag, which performs the barrier func- tion. In these systems, such as those from KeyKeg, Ecofass and Ecodraft, an aluminum foil multi-layer bag holds the product, which is never in direct contact with the PET shell, or the propellant gas. As such, this type of container is out of scope of this article, and will be considered separately at a future date. An effective barrier material is one that has a very low permeability to the gas that it is designed to work against, drastically reducing the rate of diffusion of that gas through the container wall. This is often achieved by increasing the complexity of the path that must be taken by a gas molecule as it diffuses through the barrier, the so-called tortuous path. These are often based on nylon, MXD6 being a common commercial prod- uct, or ethylene vinyl alcohol (EVOH). This tortuous path can be further enhanced by the addition of imperme- able nanoclay particles.
(a) Dolium, (b) Petainer and (c) UniKeg one-way PET kegs a b
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unique patented technical features such as an automatic safety pressure release valve, which will operate if the internal pressure exceeds 5 bar, re- sealing once the pressure has dropped to 2 bar. The six month ingress of O 2 is stated as <170 ppb, and CO 2 loss of approximately 10%. Lightweight Containers claim su- perior O 2 protection through the use of additional scavenging material in the UniKeg. At time of publication, figures were not available for shelf-life and gas barrier properties, as the product is still very new to market and under- going independent long-term trials. In- terestingly, this product features dual wall construction, designed to give a more robust keg. Due to the active O 2 scavenging component these types of container have a maximum lifetime of around 600 days from the date of preform manufacture, which is important to keep in mind when stock planning. The many advantages of this type of keg are discussed elsewhere in this issue. Coatings Barrier properties can be vastly improved by depositing a coating on the stretch-blown PET container. The coating material is usually amor- phous carbon or silicon oxide, which is applied to the internal surface with an acetylene plasma in a vacuum. To avoid cracking and flaking due to deformation of the flexible container, the coating needs to be extremely thin; just 60 to 150nm. Even so, these barriers provide excellent protection against O 2 ingress and CO 2 egress due to the intrinsically impervious nature of these materials. Very little barrier material is re- quired per container, approximately 0.04% by weight. However, additional capital investment is required for the coating plant, which must be placed inline after the preforms have passed through the stretch blow molder. Sidel’s ACTIS TM technology applies an amorphous carbon nano-coating in a high speed process of up to 44,000bph. Sidel states that a treated 330ml PET beer bottle has a shelf- life of six months, with an O 2 ingress of 1ppm and a loss in CO 2 of 10%. The Plasmax coating system, pro- duced by KHS, forms a 100nm silicon oxide layer on the inner surface. Throughputs of up to 46,000bph are possible, and integrated stretch blow molders/coaters are available. The
1. Vacuum is created inside and outside the bottle (p1 = 0.08 mbar, p2 = 50 mbar) 2. Acetylene is injected into the bottle 3 and 4. Microwave energy causes acetylene to reach its plasma state 5. Amorphous carbon is deposited on the inner wall of the bottle 6. Bottle and treatment station are returned to atmospheric pressure (p0 = 1 mbar)
Sidel’s ACTIS TM plasma coating process
Closing comments PET offers many attractive benefits to the brewer, as a low-cost, lightweight and flexible container. It is being put to good use in the one-way keg sector and has made good progress in some of the markets for bottled beer. Young- er generations of drinkers would seem to be more accepting of beer packaged in PET, having being accustomed to all types of produce being packaged in plastic their whole lives. Continual advances in barrier technology, especially those incorpo- rating active and intelligent elements, may further increase the appeal of PET bottles. As they become able to dem- onstrate the freshness of the product directly to the customer at point of sale, this technology could become an essential tool for both the producer and the consumer. References and further reading Bamforth, C. W. and Krochta, J. M., (2010) ‘Packaging and the Shelf Life of Beer’ in Robertson, G. L., Food Packaging and Shelf Life: A Practical Guide , CRC Press. Bamforth, C. W., (2011) ‘125th Anniversary Review: The Non-Biological Instability of Beer’, Journal of the Institute of Brewing, 117(4), 488-497. Briggs, D. E., (2004) Brewing : Science and Practice, Woodhead. Lange, J., Wyser, Y., (2003) Recent Innova- tions in Barrier Technologies for Plastic Packaging – a Review. Packaging Technol- ogy and Science, 16, 149-158. Acknowledgements The author would like to thank the following for their kind assistance in producing this article. Clare Ander- son (for Petainer), Paul Box (Dolium), Rudolf Brouwer (Lightweight Contain- ers), Herman Standaert (Ecodraft) and Chris Twigger (for Sidel).
technology, which is marketed under the FreshSafe PET brand, results in a beer bottle with a six-month shelf life. By removing the silicon oxide layer, using an alkaline chemical process, 100% bottle-to-bottle recy- cling can be achieved, it is claimed. Future developments With many of the quality consid- erations having been already ad- dressed, educating the consumer about the benefits of PET will be key to it finding greater acceptance in the beer sector. Many of the mis- conceptions that are held regarding PET are perhaps based on exposure to budget-priced products, where quality and freshness were not the primary considerations. As the pro- portion of people who have only ever known PET as the major container used for soft drinks increases, much of the dogma surrounding PET may disappear. Intelligent packaging systems, which are continually growing in use in the wider food industry, may aid in the growing acceptance of PET by adding a distinct advantage to the format. At a basic level, these systems can give information to the consumer about the conditions to which the package has been exposed within the supply chain. This might be in the form of a colour-changing component which will indicate if the produce has been exposed to prolonged higher temperatures, for instance. Future technology that is able to demonstrate to the customer the freshness of a product, based on quality parameters such as O 2 and CO 2 concentrations, for example, will, undoubtedly, have a great influence on their purchases.
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One way ticket How one-way PET kegs are transforming global beer export market By Annemieke Hartman-Jemmett The international beer market has undergone significant change in recent years due to consolidation by the large global breweries and, at the other end of the spectrum, rapid growth of heritage-driven microbreweries which continue to reshape the landscape as their popularity becomes entrenched in key mature markets and they expand geographically. How they deliver their products to these new markets – and the cost of the system – becomes crucial.
brewery have a lifespan of 20 years or more, the impact of intensive export or distribution over expanded routes can reduce this to less than five years. The total cost of initial investment costs for the keg pool, the cost of the constant distribution of new kegs – and the cost of repairs (which can average as much as €4 per keg per year) can be significant. There is also the consider- able cost of return transportation as well as those costs associated with the administration and handling involved in managing the keg pool. A surplus of containers is needed throughout the year to deal with sea- sonal output fluctuations, including the summer months and other peak de- mand periods. In practice, this surplus is often not available, leading to supply shortages or higher filling costs. The problems will intensify in the future as current trends indicate an increasing tendency towards smaller containers of 20 and 30-litre sizes, instead of the traditional 50-litre containers. In this situation, the cost per litre for packing beer in metal kegs increase disproportionately. Another problem facing many brew- eries is the loss of containers, often due to theft. Stainless steel is a valuable
S o as breweries grow and build their brands, many seek to expand their outlets and exploit new mar- kets. Exporting to different countries presents breweries – large and small – with a number of supply chain issues and challenges as the distance – and length of time – draught beer and
containers must travel increases dramatically. High cost of traditional kegs Investment costs in a traditional stainless-steel keg pool can be high. Whilst containers which are mostly distributed in areas close to the
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Product specification Keg body: • Lightweight monolayer construction • Moulded using PET • FDA and EU food use approved materials • Rigid with stress cracking and impact resistance • UV protection Fitting: • PP, POM construction • Compatible with beer filling and dispensing systems • Fully recyclable in normal plastic recycling infrastructure
transit for six or more weeks. During this time, fluctuating and uncontrol- lable temperatures can have an impact on the quality of the beer. The beer is often exposed to warm temperatures: 40 °C and higher are common when transporting from Europe to Asia and America or from North to South America. These tem- peratures can accelerate the chemical and physical reactions in the beer and make it age quickly. After reaching the country of destination, containers con- tinue their journey and are stockpiled until they reach their end customer. Re-transporting emptied reusable kegs is therefore slow – with circula- tion periods of a year or sometimes as long as 18 months. Independent tests show that pe- tainerKeg™ with its integrated oxygen scavenger technology has positive effects on flavour stability. On long journeys, when beer is exposed to relatively high temperatures, this can protect and preserve the original fla- vour better than stainless-steel kegs because of lower oxidation. As well as preventing oxygen from entering the container, the scavenger also removes some of the oxygen that
wholesaler. PET kegs ensure that per kilogram, much more beer is loaded each time on a full vehicle compared with beer in conventional metal kegs. This reduces overall weight, which in turn reduces fuel use and transportation costs. Again, the popular smaller sizes of metal kegs are an issue because they add to the weight of every litre of beer begin transported. By employing 20-litre PET kegs instead of 20-litre metal kegs, 50 per cent of packing material can be saved in terms of net volume. In addition, the maximum load permitted for a HGV is 25,000Kg in some European countries. If an HGV is loaded with metal kegs this limit will be reached before all available space on the truck is used. An HGV loaded with PET kegs can carry more beer and remain within the weight limit. Transport by sea Beer is usually exported overseas by ship – the most economical way. One major disadvantage in exporting, particularly over long distances, is the length of time it can take to reach destinations. Products are often in
raw material and kegs often ‘vanish’ through external use, theft or acquisi- tion by other breweries. An additional problem is that kegs used for export are often extensively damaged in circula- tion. As a result, breweries often seek to buy used, old or reconditioned kegs for export. However, they are not always available and there may also be prob- lems with old kegs because of inorganic staining and flavour taints associated with poor washing techniques. Exploring alternative options The complexities of exporting beer over long distances have led many breweries to explore alternative options. Dispos- able 20L and 30L polyethylene tereph- thalate (PET) kegs are an increasingly attractive alternative for breweries, helping them overcome the challenges of long distances as well as saving the cost of transporting empty containers back to the brewery. They can also be used on existing brewery filling lines – designed for steel kegs – which means there is no additional investment required to switch to PET kegs. One key requirement from brewer- ies looking at the export market is that the keg can be used anywhere in the world at the point of consumption. This means that that they must be compat- ible with beverage dispensing systems in use worldwide. PetainerKeg™, for example, is available with flat fittings compatible with MicroMatic A systems and well- type fittings compatible with MicroMat- ic S and D systems, and like the kegs, they are also designed for one-way use and are fully recyclable. From brewery to wholesaler Typically, beer for export leaves the breweries and is transported to a
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came with the opening of a full-scale brewery in November 2013. The 40,000-hectolitre capacity of the brew- ery dwarfs the brew pub’s 2,000-hecto- litre output. With the brewery operating at full capacity, business has now achieved record growth with revenue up 50% per year or the past three years. Steam- works brews a number of award- winning beers, some of which are on their tap year-round and some that are seasonal. Year round, Steamworks offers a its Flagship IPA which recently won Best Beer in British Columbia out of 785 entries, Signature Pale Ale, Kölsch, North by Northwest Pilsner, Jasmine India Pale Ale, Black Angel IPA, White Angel IPA and Heroica Red Ale. Eli recognised very early on that there was an interest and curiosity in the Steamworks brand, not just in the domestic market, but in the US and be- yond. International growth was always an ambition and now Steamworks is now selling products in 14 US states, as well as overseas in Hong Kong, Ger- many, Austria, Italy and Switzerland. Moving from operating a brew pub to a global business, Steamworks has had to tackle a new set of marketing, packaging and logistics challenges. This included exploring alternatives to traditional steel kegs which were too costly to use for exporting the beer. In 2014, Steamworks chose Petainer’s innovative one-way PET kegs because they offer a much more practical, lower cost, yet high-quality alterna- tive. They also provide a range of valve options which are suitable for the dif- ferent export markets Steamworks is focussing on, from Europe to Asia. Steamworks uses both the 20L & 30L petainerKeg™ with the integrated non-auto-pressure release valve (NPR) with depressurizing tool, with D Type valve and A Type Valve. Petainer’s local market presence through Petainer Can- ada also means that technical expertise and good service is readily available. Over the next five to ten years, Eli will continue to look at new opportuni- ties to grow the business and build the brand, taking the Steamworks beers to new markets where they can be enjoyed.
shape of PET kegs is a real advantage. In addition, when a PET keg is empty, it can be disposed of for recycling after releasing its pressure. This frees up storage space which was previously needed for empty metal kegs until the wholesaler’s next shipment. Microbreweries and craft beer is a success story of the past five to ten years, having enjoyed rapid growth. Consumers now demand and expect far more choice when it comes to their beer so retail outlets must provide a much wider range of draught beer products than ever before. This presents a stock challenge for the outlets. Smaller con- tainers, such as 20L or 30L PET kegs are much more practical in these circum- stances because they are emptied quick- ly. In addition, the beer can be ordered in smaller quantities – helping to reduce the need for stockpiling. Petainer is working with breweries around the world to provide packag- ing technologies which support their growth strategies, helping them to enter new markets and export their products effectively and efficiently. Case study: Steamworks Canadian brewery Steamworks chose petainerKeg™ to help it take advan- tage of emerging craft beer markets. Founded by lawyer Eli Gershkovitch in 1995 when he opened the Steamworks Brew Pub in Vancouver, Steamworks has gone from strength to strength as it has taken advantage of organic growth opportunities to increase the floor space at the original Gastown location, boosting seats from an initial 184 to 754 today, as well as adding another restaurant. In November 2013, the most significant expansion for the brewery
enters during the filling process. It has also been proven that PET containers with integrated scavenger technology tend to have fewer microbiological is- sues than those without it.
From wholesaler to final customer
When the beer arrives by ship, the sea containers are processed and relevant deliveries made to the customer or to other wholesalers. PET kegs weigh much less than metal kegs which makes them easier and safer to han- dle. Some markets have strict laws about how much workers can carry. For example, in Italy there is a law pro- hibiting workers from carrying objects weighing more than 25kg. This means that even lighter metal kegs can pose a problem – using 20L disposable PET kegs is a practical and viable alterna- tive for these markets. Reaching the end customer When the beer reaches its final destina- tion, be it a pub, bar or restaurant, ease of handling is important as is space for stockpiling. Busy retail outlets are often short of storage, so the slim, taller
Annemieke Hartman- Jemmett is Group Commercial Director at Petainer www.petainer.com
Steamworks founder Eli Gershkovitch
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