referring to the figure , a flow diagram is shown of one embodiment of a uf membrane system modified batch process for preparing a pac - enriched fruit or vegetable extract . the process begins with a clarified {& lt ; 5 ntu } pac - containing liquid feedstock { e . g ., 2 brix cranberry juice }. in the embodiment of the figure , the clarified pac - containing liquid feedstock 20 from a clarified pac - containing liquid feedstock supply 10 is fed to a uf feed tank 30 . the clarified pac - containing liquid feedstock in the uf feed tank is then pumped to a uf membrane system 40 { using a koch membrane systems model # 3838k328 - nyt spiral wound uf membrane with a 5000 mol . wt . cutoff }, with the pac - reduced permeate stream 50 transferred to a pac - reduced permeate surge tank 60 , and the pac - enriched retentate stream 70 recycled to the uf feed tank . the pac - reduced permeate is then pumped to a reverse osmosis ( ro ) system 80 { using a koch membrane systems model # tfc3838hrn1 spiral wound ro membrane } for semi - concentration { e . g ., to 18 brix }, an evaporator 90 for final concentration { e . g ., to 50 brix }, and finally to a pac - reduced concentrate storage tank 100 . the continuous processing of the clarified pac - containing liquid feedstock supply thus results in a continuous accumulation of pacs in the liquid contents of uf feed tank and uf membrane system { the aggregate pac - enriched retentate stream }. upon exhaustion of the clarified pac - containing liquid feedstock supply , the aggregate pac - enriched retentate stream can then be diafiltered with water 110 to further increase the pac dry weight content of the liquid extract through the systematic removal of residual lower molecular weight soluble solids { e . g ., sugars , acids , etc .} as permeate . the aggregate pac - enriched liquid retentate 120 { with a pac dry wt . content of at least 5 %, 10 %, 15 %, 20 %, 30 %, 40 %, 50 %, 60 %, 70 %, 80 %, or 90 %} is collected in a pac - enriched retentate holding tank 130 , and sequentially pumped to a concentrator 140 then a dryer 150 . the resultant product constituting a pac - enriched extract powder is finally transferred to a pac - enriched bulk powder storage container 160 . a suitable ultrafilter for use in the methods of the invention can have a molecular weight cutoff of about 2 , 000 - 10 , 000 dalton , about 3 , 000 dalton , about 4000 dalton , about 5000 dalton , about 6000 dalton , about 7000 dalton , about 8000 dalton , or about 9000 dalton on propylene glycol . in some cases it may be desirable to process the material in the pac - enriched retentate holding tank to separate undissolved solids . these undissolved solids can include higher molecular weight pacs and / or aggregates of lower molecule weight pacs . these undissolved solids can be separated from liquid in which they are suspended by centrifugation using , for example , a decanter centrifuge or a disk centrifuge . in some cases it may be desirable to further process the pac - reduced permeate by utilizing resin technology ( e . g ., employing amberlite ® xad7hp or amberlite ® tm fpx66 resin ) to selectively remove and recover anthocyanins and / or phenolic compounds as another phytochemically distinct extract fraction ( s ). in some cases it may be desirable to further process the pac - reduced permeate by utilizing resin technology to selectively remove and recover anthocyanins and / or phenolic compounds as another phytochemically distinct extract fraction ( s ). this fraction can be combined with a fraction that is relatively high in pacs , e . g ., the pac - enriched retentate , to obtain material that is high in pacs , anthocyanins and / or phenolic compounds and relatively low in sugars and acids . the foregoing is a description of one embodiment of the method of the invention . those skilled in the art will be able to modify the process . for example , the system may be operated in batch , modified batch or feed and bleed mode under variable temperature , pressure and flow conditions . furthermore , the system may contain membranes in configurations other than spiral wound ( i . e ., tubular or hollow fiber ), of varying polymer composition ( for example ptfe , pvdf , etc .) or inorganic membrane structures with varied composition ( for example ceramic , carbon , or stainless steel etc .) and support media . additionally , membranes other than ultrafiltration membranes may be employed such as reverse osmosis or nanofiltration membranes or charged membranes or charge - specific membranes may be employed in any manner previously described . moreover , controlled atmosphere ( e . g ., n 2 or co 2 ) techniques can be used to minimize the deleterious effects of oxidative reactions . different diafiltration media ( e . g ., acidified water ) can also be employed to stabilize and / or adjust the color of the final extract . fruit juice produced by countercurrent extraction of cranberries can be used in the methods of the invention as follows . countercurrently extracted fruit juice can be prepared as described in u . s . pat . nos . 5 , 320 , 861 and 5 , 419 , 251 , hereby incorporated by reference . briefly , frozen whole raw cranberries are provided to a cleaning stage to remove debris such as twigs , leaves , etc . and then conveyed to a sorting stage which sorts fruit to a selected size . the size - selected fruit is then conveyed to a slicing stage that slices the berries to expose the inner flesh of the fruit , unprotected by the skin . the whole cranberries are preferably cut to provide slices between 6 to 8 millimeters in width . the cleaned , sized and sliced frozen cranberries are then defrosted using hot water ( e . g ., at about 130 ° f .) to a temperature of less than 75 ° f . ( e . g ., 65 ° f .) and conveyed to the solid input of an extractor stage which employs a countercurrent extractor described in detail in u . s . pat . no . 5 , 320 , 861 . the liquid input to the extractor is typically derived from a fruit - derived water supply . the liquid output of the extractor stage is a high - quality extract mixture of fruit - derived water and fruit juice , which is collected for further treatment and use in the methods of the invention . in addition , the extracted fruit can be used as a fruit feed stock to produce additional juice that can be used in the methods of the invention . a number of embodiments of the invention have been described . nevertheless , it will be understood that various modifications may be made without departing from the spirit and scope of the invention .
a method for producing a proanthocyanidin extract is described . the method comprises : providing a volume of proanthocyanidin - containing liquid feedstock ; passing the proanthocyanidin - containing liquid feedstock to an ultrafiltration feed tank ; filtering the material in the ultrafiltration feed tank through an ultrafiltration membrane system to fractionate the material into a proanthocyanidin - reduced permeate stream and a proanthocyanidin - enriched retentate stream ; collecting the proanthocyanidin - reduced permeate stream ; and passing the proanthocyanidin - enriched retentate stream to the ultrafiltration feed tank until the volume of proanthocyanidin - containing liquid feedstock is exhausted and thereafter collecting the proanthocyanidin - enriched retentate stream .