PROCESSING OF BEVERAGES AND DRINKING WATER

Clarification of apple juice. Inorganic membranes have been utilized in two ways in the production of apple juice. One is to clarify pressed or prefiltered apple juice and the other is to extract clarified apple juice directly from apple puree or pomace. Microfiltration of apple juice has been one of the most successful commercial applications of inorganic membranes. 

To maximize the permeate flux using 0.2 im zirconia membranes on carbon supports, a TMP of 3.5 bars and a crossflow velocity of 5 to 6.5 m/s at 30 and 50 C are 

Using a two-stage, single-pass module of food-grade dynamic metal oxide membrane on a sintered stainless steel support tube under a TMP of approximately 20 bars and a temperature of 50 C, Thomas et al. [1987] have successfully clarified apple puree with a juice yield of 86% and a steady state flux of about 85 L/hr-m. The quality of the clarified apple juice by this dynamic or formed-in-place membrane is excellent -sparkling looking and flavor retained. As much as 65% reduction in the total pectins has been attained. 

Clarification of other fruit juices. Clarification of cranberry juice has also been practiced commercially using ceramic membranes recently. Through a series of tests with alumina microfilters, Venkataraman et al. [1988] determined that the optimal pore diameter is about 0.45 pm with respect to the permeate flux and the clarity of the 

Several fruits and vegetables such as apples, pears, pineapples, peaches, carrots and beets have been pilot tested with promising results [Swientek, 1987]. In addition, strawberry and kiwifhiit juices have also been clarified using ceramic membranes. 

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