The problem of protecting beer in plastic bottles against oxidative deterioration and the loss of carbonation is discussed. It is pointed out that while PEN, laminated materials combining layers of PET with layers of gas barrier compounds and systems for coating the inner or outer surfaces of PET bottles with silicon oxide (or some other substance with similar properties) all give much better protection than plain PET, they are all much more expensive than plain PET. An alternative solution, developed at the Licher Brewery, consists in the use of plain PET bottles which, immediately after filling, are placed in suitably shaped bags of gastight metallized plastic foil, from which the air is excluded by means of an inert gas (such as carbon dioxide or nitrogen) before or during the insertion of the bottles and which are sealed immediately thereafter. This outer packaging is claimed to give beer in a plain PET bottle the same shelf life as it would have in a glass bottle. It is also cheap, readily available, easy to handle and fully recycleable. The invention is stated to be the subject of a German patent application (DE 10217114).
