PETpla.net Insider 06 / 2012

Fig 1:The amount of oxygen which dif- fuses through the packaging into the beverages increases as the thickness of the packaging decreases. BEVERAGE PREPARATION 30 PET planet insider Vol. 13 No. 06/12 www.petpla.net sensitive BEVERAGES BEVERAGE PREPARA well in bottles with higher permeability. It can be stated that the effect of oxygen on product quality is highly variable and depends on the formulation in question: the same oxygen ingress can have very different effects, depending on the fla- vour or product composition. Increasing the amount of ascorbic acid as an anti- oxidant in products A, B and C cannot always compensate for the sensory changes which occur during the prod- uct’s shelf-life. By contrast, the use of scavengers can offset or even overcom- pensate for the effects of lower weight. www.wild.de How P.E.T.proof works - results Wild developed the quick-test procedure P.E.T. proof in 2003. It is a comprehensive stress-test program which reproduces six months’ worth of real-time cumulative oxygen permeation within a period of four days. P.E.T. proof also makes it possible to depict real permeation data in a graph which shows the increases in oxygen levels inside the bottle. As a result, Wild can track values indicating the influence of the bottles, caps and filling processes on overall oxygen ingress. The method involves a non-invasive optoelectronic quantification of oxygen, the OxyTrace system, which is made by PreSens in Regensburg, Germany. In this context, non-invasive means that the bottle does not have to be opened to determine the neces- sary values: the values can easily be calculated into real permeation rates. In other words, P.E.T. proof is not a form of theoretical modeling; it docu- ments real data. Every pattern on the graph can be supported by sev- eral hundred individual values, thus permitting high precision levels in the measurements. The samples also undergo parallel sensory analysis by a trained tasting panel using a difference-from-control test. P.E.T. proof was validated using several types of beverages: the results of P.E.T. proof tests and real-time tests were compared in analytical and sensory evaluations of products in different kinds of plastic bottles. In comparison to real-time tests, P.E.T. proof successfully yielded a very precise simulation of the effects that varying levels of oxygen permeability had on different types of bottles. Wild uses the process exclusively for products developed in-house. The process is internationally patent-protected and has become the company’s bench- mark standard test procedure for new developments in the beverage sector. Fig 2: The oxygen ingress in the bottle which weighs 19.8 grams is 33% higher than in the 24g bottle. Fig. 3: In a test of the sensory stabil- ity of orange sodas, three different prod- ucts were filled in seven PET bottles with different prop- erties. The influence of the closure Wild can also use P.E.T. proof to iso- late the influence of the closure and its impact on oxygen permeation. Another test sequence analysed a PET preform rather than a PET bottle. The thick and even structure of the preform gives it a reproducibly low rate of permeability; for the purposes of comparing the effect of the closure, this yields a constant “back- ground noise“ which can be very easily distinguished from the fluctuating perme- ability rate of the closure. Wild compared the permeability of standard caps with that of barrier caps. Barrier caps feature a plastic lining of lower permeability. The results of the test show that the choice of closure can have a clear impact on the overall permeability of the packaging. Conse- quently, the closure must be included in the total analysis of a bottle’s perme- ability. Sensory stability Wild filled three different products into seven different kinds of PET bottles so it could attain robust data about the influence of the thickness on perme- ability and subsequently on the sensory stability of beverages(Fig. 3). The bottles were 21 and 24g monolayers (ML); 21 and 24g PET bottles which consist of 50% recycled PET and 50% new PET (RH), and three different scavenger ver- sions with a bottle weight of 21g each. Products A, B and C were orange sodas with different flavourings but the same amount of sugar. During the filling pro- cess, 400mg/l ascorbic acid was added to each of the three. As part of the P.E.T. proof method, products also underwent a difference- from-control test. The results were expressed on a scale ranging from 0 – 15 (0 = identical to the reference; 15 = very different from the reference): In comparison to the reference product in the taste test, no significant difference could be detected in the sample up to a value of 3, which was defined as the significance threshold. The rejection limit was set at 7.5, meaning products at that value or higher were deemed no longer marketable. The test results confirm that there are products which do not function 35 30 25 20 15 10 5 0 oxygen content [mg/l] 0 1 2 3 4 5 6 7 real time equivalent [m] 19,8 g/Fl. y=5,0201x R²=0,99244 21 g/Fl. y=4,3024x R²=0,99044 24 g/Fl. y=3,7723x R²=0,99016 15,0 13,5 12,0 10,5 9,0 7,5 6,0 4,5 3,0 1,5 0 Line scale value 21 g ML 21 g RH 24 g ML 24 g RH Scavenger 3 Scavenger 1 Scavenger 2 injection limit significance thresold prod. A prod. B prod. C