Effect of fractal flocculation behavior on fouling layer resistance during apple juice microfiltration |
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| Affiliation: | 1. Dipartimento di Scienze e Tecnologie Biologiche Chimiche e Farmaceutiche (STEBICEF), Università degli Studi di Palermo, Parco d''Orleans II, Viale delle Scienze, Edificio 16, 90128 Palermo, Italy;2. Dipartimento di Scienze Agrarie, Alimentari e Forestali, Università degli Studi di Palermo, Parco d''Orleans II, Viale delle Scienze, Edificio 4, 90128 Palermo, Italy;3. Dipartimento di Scienze Biomediche, Odontoiatriche e delle Immagini Morfologiche e Funzionali- Università di Messina, A.O.U. Policlinico \"G. Martino\" Via Consolare Valeria, pad. G, Torre biologica, 98125 Messina, Italy;4. Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Università di Messina, Stagno d''Alcontres, 31-98166 Messina, Italy;5. ISOF - CNR Area della Ricerca di Bologna, Via P. Gobetti 101-40129 Bologna, Italy;6. Dipartimento di Chimica “Giacomo Ciamician”, Alma Mater Studiorum, Università degli Studi di Bologna, via F. Selmi 2, 40126 Bologna, Italy;7. Dipartimento di Scienze della Terra e del Mare (DiSTeM), Università degli Studi di Palermo, Via Archirafi 10, 90123 Palermo, Italy;8. Consorzio Interuniversitario di Ricerca in Chimica dei Metalli nei Sistemi Biologici (C.I.R.C.M.S.B.), Piazza Umberto I, 70121 Bari, Italy |
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| Abstract: | The colloidal material in juice obtained from Red Delicious apples held in cold storage for over 6 months was observed to spontaneously aggregate to form ordered flocculation patterns. These flocculation patterns could be altered by heat treatment and by gelatin or antioxidant addition. The specific resistance of the fouling layer produced by each juice during microfiltration could be qualitatively predicted by examining the structure of macroscopic flocculation patterns. Environmental scanning electron microscopy (ESEM) photos of the various hydrated fouling layers indicated that loose flocs appeared to compress and rearrange on the membrane surface, producing smooth, low porosity secondary membranes. Densely packed cross-linked aggregate networks also formed low porosity structures, once again creating a fouling layer with high resistance. The lowest resistance fouling layers were produced when the flocs were dense enough to resist compression but porous enough to provide pathways for permeate flow. Field emission scanning electron microscopy (FESEM) and ESEM images indicated that, in many cases, the spacial distribution of solids in the microscopic aggregates were reminiscent of those in the macroscopic flocs. Such scaling relationships are typical of fractal systems. |
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