Keg Science and Testing

All products are subject to exhaustive organoleptic, logistics and heat tests by Petainer’s own labs and by globally recognised independent institutions such as VLB, TOPA Institute and Hochschule Geisenheim University.

When it comes to using PET kegs, one of the most frequently asked questions is that of product quality and protection.  We recognise that if our customers’ products do not arrive in optimum quality to be served in bars, restaurants and cafes, their reputation and brand is at risk.

That’s why all our products are subject to exhaustive organoleptic, logistics and heat tests by Petainer’s own labs and by globally recognised independent institutions such as VLB, TOPA Institute and Hochschule Geisenheim University.

Suitability of petainerKeg for draught packaging of beer

We commissioned VLB Berlin, an independent and highly regarded authority on the beverage industry to compare beer quality in our PET kegs to other packaging types.  An independent panel test evaluated and compared beer in petainerKeg and steel kegs.

The trial concluded that over nine months, the development of the different beers tested was generally similar when stored in metal and in PET Kegs, leading to the conclusion that PET and metals have similar performance along the storage time.

The impact of bottling and storing wine in petainerKeg

We asked Hochschule Geisenheim University to look at the difference between wine stored in a petainerKeg and metal kegs.  These tests showed that petainerKeg delivers the wine with a visual appearance on par with wine stored in glass bottles and metal kegs, and does not negatively impact on sensory experience or taste quality thanks to a combination of active and passive barriers maintains gas barrier properties for storage of wine.

Impact of bottling and storing wine in Petainer                    Performance of PET vs. Metal Keg containers

The science of one-way PET kegs

In a recent article published by Brewing and Beverage Industry International, an authoritative and highly regarded industry publication, Petainer’s team explain why our products are the most tested on the market.

The science of one-way PET kegs – why independent testing and validation is key

Erin Corstanje, Group Director New Product Development, and Sonia San Martin, Senior Scientist, Petainer

The science of one-way PET kegs – why independent testing and validation is key

As beer is shipped across the glove, one-way PET kegs are getting more and more popular.  Modern PET kegs’ functional performance and food protection is comparable to that of traditional packaging such as steel kegs and glass bottles.

As experts in high stretch polymer engineering, the team at Petainer have been able to apply their design knowledge and expertise in resins to develop superior plastic containers that meet and exceed the operational and functional demands of the market.

Petainer has focused on three key aspects affecting the functionality of plastic kegs: UV/light exposure, transportation and temperature. The method of applying rigorous testing and use of globally accredited Universities and independent laboratories to validate petainerKeg separates Petainer from its competitors. We see both the use of independent testing and rigorous validation as critical to support the strong global and regional brands that Petainer delivers to. Giving them the confidence to move forwards with a one-way keg solution.

From the beginning, the need for light and UV protection for its contents has always been met by petainerKeg.   Now Petainer’s the new next generation Hybrid keg takes that protection one step further, removing the need for the carton and selecting colours that hold the highest Light Fastness grading and UV, providing maximum protection to the contents.   petainerKeg have been tested following guidelines from standard (ISO 4892/ASTM G154) accelerated weathering testing, by QUV up to 750h (equivalent of 9 months exposure) to show that colour, UV protection and PET properties are retained through the life of the keg.

With the geographical expansion of petainerKeg, our customers are looking for more assurances when transporting product by road and sea freight.  Therefore, Petainer now tests and validates its products like Hybrid keg to international standards using ASTM D4332-14, ASTM D4169-14 for testing shipping containers use with handling, impact, drop, 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 petainerKeg over long distance transport. Petainer has submitted filled and empty kegs to rigorous external testing which demonstrate the success of the product in road and sea freight trials.

A further aspect of plastic kegs is the performance when exposed to unpredictable temperatures, either for a long period of time during storage or for short high temperature peaks during transport.  As plastic kegs are transported farther to open new market potential, alternative no temperature-controlled transport is being utilized to maintain the lowest cost per litre of product.  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 key concerns.

For carbonised drinks such as beer, temperature has an impact on the amount of internal pressure exerted on the PET container. Following Henry’s Law for gases, the CO2 will transfer with higher temperature from the liquid to the gas phase of the container and increase its partial pressure on the PET keg. Over time this can cause the plastic container to creep or expand depending on the specific keg characteristics.

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 20oC and 30oC for more than 90% of the Earth’s surface (desert locations excluded).  Locations like Thailand have reported year average of 32.3oC with a maximum of 39oC (April 2016). A different scenario is the conditions during transport. In a sea freight container, temperatures may peak at midday up to 50oC or higher but cool down after a few hours and over-night. There is also the factor of heat convection through a large quantity of filled kegs. Even if the ambient air is at 50oC the actual keg and its contained liquid will take that heat at a much slower pace, meaning the overall effect of temperature on the keg is less.

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 key point differentiation between steel and plastic kegs, leading some people to equate expansion to safety.  However, through this study Petainer has demonstrated petainerKeg has minimal expansion and excellent container strength.

Petainer has used data from internal testing done in climatized chambers and guided by the references in the ASTM standards of sample conditioning for transport. Petainer tested samples at 30oC for up to 4 consecutive weeks, at 40oC for up to 2 weeks and at 50oC up to 1 week simulating sustained temperature conditions.   Under normal conditions, temperature fluctuations will only reach those values for several hours a day, but the experiment was designed to apply maximum stress to the kegs.  Assuming a keg may achieve 6 hours at a temperature, then 4 weeks at 30oC would equate to around 4 months of real-time exposure, while 2 weeks at 40oC would be 2 months and 1 week at 50oC about 80 days.

For each set of samples, petainerKegs were conditioned at 20oC for a week before control measurements were taken for dimensions, and O2 and CO2 content. They were then placed in climatized chamber at the set temperature and taken out at intervals of 1 day, 3 days and 7 days then moving to once a week until the end of the experiment. The heat-treated samples were conditioned at 20oC before remeasuring.

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

The oxygen barrier was retained with no increase in O2 levels at any temperature during the entire experiment.  Carbon dioxide retention on the other hand was affected by the temperature.  PetainerKeg specification for CO2 retention of <15% loss is based on brewing industry standards; Petainer found that petainerKeg could support this specification for 4 continuous weeks at 30°C and 35 weeks at 22oC.  Similarly, petainerKeg can be stored for 1 week at 40°C, and 25 weeks shelf life at ambient (22oC).  No other keg in the market has been tested to this extent.

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