The microfiltration of foodstuffs to pasteurise them is limited by the build up of fouling materials on the surface of the filtration membrane as well as the phenomenon of concentration polarization (Marshall et al., 1993). It would appear however that using ultrasound technology might just be the answer.
A number of techniques have been applied in the past to improve flux across membranes ranging from the use of in-line turbulence promoters, pulsed flow and back-flushing, to the use of enzymes and strong alkaline cleaning agents to clear foulants. Ultrasound applications however, have been steadily developing as one of the most effective non-invasive method for many years, improving flux in both microfiltration and ultrafiltration (Kyllönen et al., 2005).
One recent application adds further weight to applying ultrasound to improve the microfiltration of milk in this case, during processing by up to 33% (Mirzaie and Mohammadi, 2011). The study reports on suggested mechanisms for improvement in flux including cavity bubbles to dislodge protein (Latt and Kobayashi, 2005). In the most recent study, the authors found that continuous application was preferable to pulsed applications.
References
Kyllönen, H.M., P. Pirkonen and M. Nyström. (2005) Membrane filtration enhanced by ultrasound: A review. Desalination 181 pp. 319–335.
Latt, K.K., Kobayashi, T. (2005) Ultrasound-Membrane Hybrid Processes For Enhancement Of Filtration Properties. Ultrasonics Sonochemistry 13 (4) pp. 321-328
Marshall, A.D., Munro, P.A., Tragardh, G. (1993) The effect of protein fouling in microfiltration and ultrafiltration on permeate flux, protein retention and selectivity: a literature review. Desalination 91 pp. 65–108.
Mirzaie, A., Mohammadi, T. (2011) Effect Of Ultrasonic Waves On Flux Enhancement In Microfiltration Of Milk. J. Food Eng., doi:10.1016/j.jfoodeng.2011.07.026
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