Membrane filtration equipmentUnpasteurized raw apple juice processed by microfiltration (MF) or ultrafiltration (UF) was evaluated for quality and the methods compared for process efficiency. Juice permeate was analyzed for total solids, soluble solids, color, turbidity, pH and acidity. Apple juice processed by MF was significantly (~~0.05) darker, more turbid, contained higher total and soluble solids than juice processed with UF, and was preferred by a taste panel. MF processed more permeate per unit time than UF under similar operating conditions with no noticeable difference in power consumption (watt-hr/L).
An ultrafiltration system fouled by pectin solutions was used as a model system. The fouled membrane flux was fully restored by circulating 0.5% NaOH solution for 1 hr. By adding 0.003% poly(ethylene oxide) in 0.5% NaOH solution, the cleaning time required to fully recover flux of the fouled membrane was reduced to 2 min. The mechanism of improving cleaning efficiency may not be wholly attributed to the scouring effect of the polymer on the membrane surface. The cleaning and rinsing results suggest that polymers in cleaning solutions convert the pectin foulant into a foulant-polymer complex which could be readily rinsed from the membrane surface by water.
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