Ultrafiltration membrane system fine-tunes juice processor's operation

Clermont Inc., a medium-sized fruit juice producer in Cornelius, Ore., processes apple juice and about 20 other juices for the food ingredient market. Some juices, such as black raspberry, are so specialized that the company spends just a few days processing them each year.

The early cellulose acetate reverse osmosis membranes were delicate, of inconsistent quality, and low in capacity. Systems were expensive to install and operate. While these and other problems slowed the commercialization of early membrane processes by the food industry, the early results were encouraging enough to promote further development of the technology.The use of UF membranes to separate monosaccharides and disaccharides from corn sweeteners has been reported in the trade literature.In the future, however, these advantages should translate into wider application in food processing.Reverse osmosis was first used to desalinate water. Its applicability to heat-sensitive foodstuffs such as juices, extracts, and milk was recognized but problems were encountered, the primary one being fouling. Retained solutes would also build up near the membrane surface, slowing water removal and decreasing the system's throughput.* Reverse osmosis (RO) retains the smallest of molecules, passing only solvents such as water and alcohol. It is the oldest of the membrane separation processes.George Hutson, president of a Minneapolis-based membrane systems engineering firm, cites its successful application to the demineralization of salty whey, sweet whey, and casein in large U.S., European, New Zealand, and Australian commercial establishments. Other applications include fractionation of sugar streams, and concentration and cleanup of UF permeate and meat and gelatin protein streams.* There is no haze in the juice because the system is more temperature-stable and has a lower molecular weight cutoff level.The newest developments in this area concern processing WPC with a very high protein level (up to 80 percent) and low fat content. The 80 percent WPC product is already being made by a number of processors using ultrafiltration (UF). Removing fat is a more difficult problem and no one in the United States is known to be doing it, although a fat-removing membrane process has been patented and used in Europe.

Says Eischen: "The ultrafiltration system has served us better than expected. It takes care of all of our major filtration needs from early June when fresh strawberries start trickling in through the end of pear season at the end of August, when we're cranking six days a week, right through our frozen season in winter."