Following on from the overview of the principles of pasteurization in general and the pasteurization of beverages (especially carbonated soft drinks) in PET (or other plastic) bottles in particular in Part 1 of this paper (Brauwelt, 14 Sept. 2006, 146(37), 1102-1106) and that of the plastic bottle manufacturing process and the properties of plastic (plain PET, PEN or combinations of PET with various gas barrier enhancing materials) bottles, as well as closures and closure linings for them, in Part 2 (Brauwelt, 12 Oct. 2006, 146(41/42), 1242-1246), the results of experiments intended to compare the ability of 3 different bottles (a laminated type having an oxygen scavenging layer sandwiched between 2 layers of PET, a PET bottle with an internal gas barrier coating of a form of carbon and one made of a blend of PET and a gas barrier enhancing material called MXD6, of which last type 3 variants, with 2, 5 and 8% MXD6 respectively, were tested) and 4 closure types (an unlined high density polyethylene screw cap, lined polypropylene copolymer screw caps (with or without sulphur trioxide added to the lining as an oxygen scavenger) and steel crowns similar to those used on glass beer bottles (which last were used only on the PET/MXD6 blended bottles)) to withstand the effects of a typical tunnel pasteurizing process (when filled with carbonated water) are presented and discussed. All the bottle/closure combinations tested were damaged by the heat of pasteurization to a degree sufficient to have detrimental effects on products contained in them, including loss of carbonation due to bottle deformation, as well as increased oxygen uptake despite the gas barriers and/or oxygen scavengers present.
