Rough Beer Clarification by Crossflow Microfiltration in Combination with Enzymatic and/or Centrifugal Pretreatments

Abstract

In this work, crossflow microfiltration performance of beers, characterised by different turbidity levels (at 20°C) in the ranges of 2.4-52.4 EBC unit, was assessed in a bench-top plant, appropriately designed and equipped with a 0.8-µm ceramic tubular membrane module, under constant feed superficial velocity (v_S = 6 m s^-1), transmembrane pressure difference (TMP = 3.74 bar), temperature (~10 °C), and periodic CO₂ backflushing. The quasi steady-state flux (J_v,ss) was reached after about 1 h, independently of the turbidity (H) of rough beer. Its decline was drastic as H increased from 0 to 2-3 EBC unit and tended to an asymptotical value of 91 ± 8 dm³ m^-2 h^-1 for H > 7 EBC unit. By removing yeast cells and larger aggregates via centrifugation, or hydrolyzing firstly the gel forming polysaccharides and, secondly, get rid of the suspended solids by centrifugation, it was possible to increase J_v,ss to 137 ± 13 or 294 ± 30 dm³ m^-2 h^-1. Periodic CO₂ backflushing of rough beer resulting from combined enzymatic and centrifugal pre-treatments was able to lower the overall hydraulic resistance to (5.2 - 8.1) x 10¹¹ m^-1, values near to the resistance of clean membrane.