Abstract
Crossflow membrane technologies were used to clarify and concentrate the raw extract of bitter substances from hot trub, a brewing by-product, seeking to produce an alternative route for hop products via a study performance and fouling investigation. Microfiltration was performed in concentration (MF/CO) and diafiltration (MF/DF) operation modes, feeding with extract composed of lupulone/analogs (∼6 mg/g), iso-α-acid (∼4 mg/g), and humulones/analogs (∼2 mg/g). The MF/CO had ∼69 % bitter substances permeation, while the MF/DF exhibited an increase of about 22 % in relation to MF/CO only (achieving 81–92 % the bitter substances permeation), being colupulone and n-+adlupulone presenting minor retention (<16 %). Adding the diafiltration step had not modified the profile of permeate fluxes curves, which was close to the exhibited by MF/CO. Concerning the sequential nanofiltration approach, six commercial membranes with different thin-film features and nominal molecular weight cut-offs ranging from 1000 to 150 g/mol (NP010 ≥ UA60 > NP030 > XN45 > NF9 > HL) were tested, operating with a clarified extract from MF/DF. XN45 and HL membranes presented higher bitter substance retention with less flux decay (∼42 %) than others. Membrane surfaces were altered after filtrations in relation to chemical profiles, morphology, and hydrophobicity, indicating a foulant layer formation. Different compositions and morphology of foulant layer were observed, being proteins the principal fouling agent for microfiltration while bitter substances were the main agent for nanofiltrations.
Published Version
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