Merin, U., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Shomer, I., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel

During ultrafiltration of orange juice with inorganic membranes, heating of the juice prior to the filtration experiment resulted in a significant increase of the fouling indices. The effect of the irreversible fouling (Rif) was always high, whereas the reversible fouling (Rrf) depended on the treatment. It was clearly seen that fouling was reduced after pectin degradation, but the heat treatment applied to the juice before filtration still resulted in reduced fluxes. It is suggested that pectins and proteins that undergo flocculation/coagulation during the heat treatment tend to interact with the membrane-filtering layer and to cause reduction of permeation flux. To clean the membrane to restore its pure water flux, close to the initial one, a proteolitic enzyme detergent wash was needed.