Practical experiences of packaging beer in pet bottles.
Oag, I.D.M. and Webb, T.J.B.
The experience of one brewing company in bringing beer to market in polyethylene terephthalate (PET) bottles is detailed. PET bottles are attractive in being cost competitive, lightweight, shatter proof, odourless and taint free. PET in bottle form is a poor barrier to water vapour, carbon dioxide and oxygen and leads to poor shelf life of the beer. However, external coating of the bottles with polyvinylidene chloride PVdC reduces the rate of carbon dioxide loss and oxygen pickup, as measured by the development of haze and unacceptable flavours, and extends shelf life beyond 20 weeks. There are occasional problems associated with blistering and flaking of the PVdC coating. Bottles must be stored in a cool, clean and dry environment because of their high flammability, tendency toward heat distortion and the need to preserve their near sterility at manufacture. Because preevacuation of the PET bottle is not possible it is necessary to ensure that beer DO is low, bottle fill in quiet and top space air removal is effective. The heat sensitivity of PET bottles precludes tunnel pasteurisation necessitating aseptic filling with flash pasteurised beer and subsequent rigorous microbiological quality control. Using high quality wraparound labels of metallised paper and correct choice of glue, tearing of labels due to post filling bottle expansion has not been a problem. Early problems with reduced strength and stability of palletised loads due to condensation in the filled cases have been resolved by the introduction of ventilation holes in cases and by leaving warehoused pallets undisturbed for 7 days thus allowing condensation to evaporate.
Keywords: beer bottling filling plastic bottle polyethylene