The Sterile Filtration and Packaging of Beer into Polyethylene Terephthalate Containers

Abstract

This paper describes the successful practical development of a system for the sterile filtration and aseptic packaging of beer into 2-L polyethylene terephthalate (PET) bottles. The major factors resulting in poor filterability were found to be colloidal carbohydrates and the use of coarse grades of kieselguhr in a single-pass filtration regime. The filterability of the beer through high-capacity prefilters followed by 0.45-μm Millipore membrane filters was greatly improved by addition of μ-glucanase in the mash tun and optimization of the single-pass kieselguhr filtration. Microbiological stability of the beer was achieved primarily by filtration through 0.45-μm Durapore membranes and secondly by adherence to stringent quality assurance procedures with regard to the filling operation. Although the specification of nil microorganisms in the bottle was not always achieved, no beer spoilage was observed. These microorganisms possibly found ingress through contaminated bottles and closures. Our experience supports the findings of similar operations showing that the success of sterile filtration and aseptic packaging lies in good “quality assurance” procedures.