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PET Kegs And Assuring Beer Quality

The best ways to test one-way PET kegs for UV, light exposure, transportation and temperature

One-way PET kegs are getting more and more popular because they represent a low-cost alternative to traditional steel kegs. They offer significant supply chain benefits, helping brands overcome the challenges of long distances as well as saving the cost of transporting empty kegs back to the producer. But how does one know if a PET keg has been adequately tested to protect your beer?

The product development team at Petainer has been able to apply its design knowledge and expertise in resins to develop exceptional plastic containers that meet and exceed the operational and functional demands of the market. They have focused on three key aspects affecting the functionality of plastic kegs: UV/light exposure, transportation and temperature.

Our products hold superior Light Fastness grading and UV, providing maximum protection to the content. Petainer kegs have been tested following standard of ISO 4892/ASTM G154, accelerated weathering testing, (QUV) to show that colour, UV protection and PET properties are retained through the life of the keg.

With the geographical expansion of one-way kegs, customers are looking for more assurances when transporting product by road and sea freight. Therefore, Petainer now tests and validates its products, like the Hybrid keg, to international standards ASTM D4332-14, ASTM D4169-14 for testing shipping containers, and ASTM D4728 for road freight, which uses parameters agreed from world global data on road conditions. These tests are designed to anticipate how the average amount of mechanical stresses and temperatures impact the keg over long-distance transport. Petainer kegs have been tested successfully.

A further aspect of plastic kegs is the performance when exposed to unpredictable temperatures, either for an extended period during storage or for short high-temperature peaks during transport. As plastic kegs are transported farther, alternative non-temperature controlled transportation is being utilised to maintain the lowest cost per litre of product. For carbonised drinks such as beer, the temperature has an impact on the amount of internal pressure exerted on the PET container. Over time this can cause the plastic container to creep or expand depending on the specific keg characteristics. For this reason, the barrier protection to gas permeation through both the loss of carbonisation and the increased ingress of oxygen in the container as well as the physical expansion and strength of the keg are vital concerns.

When faced with the challenge of evaluating keg behaviour at temperature, Petainer considered available reports on annual temperature averages around the world that showed maximum average between 20°C and 30°C for more than 90% of the Earth’s surface (desert locations excluded). Places like Thailand have reported year average of 32.3°C with a maximum of 39°C (April 2016). Transport represents a different scenario: in a sea freight container, temperatures may peak at midday up to 50°C or higher but cool down after a few hours and over-night.

During a six-month intensive analysis, Petainer measured over 500 kegs, studying the relationship between various temperatures with expansion, carbon dioxide retention and prevention of oxygen ingress. Thermal expansion has always been a critical point of differentiation between steel and plastic kegs. However, this study has demonstrated that its keg has minimal expansion and excellent container strength.
Petainer tested samples at 30°C for up to 4 consecutive weeks, at 40°C for up to 2 weeks and 50°C up to 1 week simulating sustained temperature conditions. Under normal circumstances, temperature fluctuations will only reach those values for several hours a day, but the experiment was designed to apply maximum stress to the kegs.

We found that the level of expansion of the kegs was minimal (<4%) even at 50°C for 72 hours and closure fittings maintained the hermetic seal. The level of expansion was temperature-driven, and once it was achieved, there was only minimal additional expansion with extended time. Functionality and drop tests showed that Petainer keg was fully functional even after exposure.

The oxygen barrier was retained with no increase in O2 levels at any temperature during the entire experiment. Predictably, carbon dioxide retention was affected by heat changes. Our keg specification for CO2 preservation of <15% loss is based on brewing industry standards: it could support this specification for four continuous weeks at 30°C and 35 weeks at 22°C. Similarly, it can be stored for one week at 40°C, and 25 weeks of shelf life at ambient (22°C).

Petainer has raised the validation testing of all its products to ensure the highest standards are delivered to the customers. Overall, data has shown our keg minimises expansion at elevated temperatures allowing its transportation while maintaining functionality and strength.

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