Towards a Kieselguhr- and PVPP-Free Clarification and Stabilization Process of Rough Beer at Room-Temperature Conditions

Abstract

In this work, the main constraint (that is, beer chilling and chill haze removing) of the current beer conditioning techniques using Kieselguhr filtration and Polyvinylpolypyrrolidone (PVPP) treatment was overcome by developing a novel higher-throughput conditioning process, operating at room temperatures with no use of filter aids. The effect of filtration temperature (T_F ) in the range of 0 to 40 °C on the hydraulic permeability of ceramic hollow-fiber (HF) membranes with nominal pore size of 0.2 to 1.4 μm, as well as on their limiting permeation flux (J^* ) when feeding precentrifuged rough beer, was preliminarily assessed. When using the 1.4-μm HF membrane operating at T_F ≥ 20 °C, it was possible to enhance the average permeation flux at values (676 to 1844 L/m² /h), noticeably higher than those (250 to 500 L/m² /h) characteristics of conventional powder filtration. Despite its acceptable permanent haze, the resulting beer permeate still exhibited colloidal instability. By resorting to the commercial enzyme preparation Brewers Clarex® before beer clarification, it was possible to significantly improve its colloidal stability as measured using a number of European Brewing Convention forcing tests, especially with respect to that of precentrifuged rough beer by itself. By combining the above enzymatic treatment with membrane clarification at 30 °C across the ceramic 1.4-μm HF membrane module, it was possible to limit the haze development due to chilling, sensitive proteins, and alcohol addition to as low as 0.78, 4.1, and 4.0 EBC-U, respectively, the enzymatic treatment being by far more effective than that using PVPP.

Practical application: A novel Kieselguhr- and PVPP-free rough beer conditioning process at room temperatures was set up. By submitting precentrifuged rough beer to commercial preparation Brewers Clarex ® and then to membrane clarification at 30 °C across a ceramic 1.4-μm hollow-fiber membrane module, it was possible to obtain a clear and stable beer with a throughput (1306 ± 72 L/m² /h) by far higher than that (250 to 500 L/m² /h) characterizing the current powder filters. The haze development due to chilling, sensitive proteins, and alcohol adding was by far lower than that observed when microfiltering PVPP-pretreated rough beer.

Keywords: Brewers Clarex® and PVPP; ceramic hollow-fiber membranes; colloidal stability forcing tests; filtration temperature; limiting permeate flux; membrane porosity.