A comparative study of the respective effects of pasteurization by plate heat exchanger, pasteurization in bottle and three stage sterile membrane filtration on the quality and stability of four Swedish lagers is described. For each treatment category, bottles of each beer (plus cans in the case of plate pasteurization), with dissolved oxygen contents at packaging of either 0.2 or 0.7 ppm, were stored at room temperature for up to 15 weeks. Samples were tasted at regular intervals and their haze and foam stability determined. Certain samples of one brand were also analysed for aroma volatile constituents. Little difference was observed between treatment categories as regards flavour stability. While increased oxygen had an adverse effect on stability (as expected), the alcohol content (which varied from 1.7 to 4.4% by weight) had no significant influence. Foam stability (determined by the Rudin method) decreased more rapidly in the sterile filtered beer than in beer pasteurized by either method. This observation, together with the higher costs of sterile filtration, is regarded by the authors as a telling argument in favour of pasteurization.
Keywords : beer comparative test pasteurisation quality stability sterile filtration