Abstract: A naturally acidic, edible fruit or vegetable juice containing a significant concentration of suspended matter, such as pulp, is effectively subjected to ion exchange without substantial loss in pulp content by passing the juice through a supported laterally confined particulate bed of a weak base anionic resin in an upwardly flowing direction through the bed at a liquid velocity which is sufficient to cause the bed to undergo a vertical expansion of at least about 20-25% by volume and preferably 50% but not so great as to cause significant entrainment of resin particles in the treated juice. The volume of the resin relative to the throughput of juice is large enough to extract a substantial amount of the natural acidity of the juice. Preferably, the juice is passed through the bed at a rate sufficient to impart to the expanded bed a slowing rolling motion at least in the region adjacent its upper surface.