Abstract: A reverse osmosis method of concentrating fruit juices wherein a major portion of the fruit juice sugars are removed in a reverse osmosis first stage from the fruit juice at about room temperature and a pressure in the range 500 to 1500 psi, using porous cellulose acetate membrane material, while flavor compounds are removed in a reverse osmosis second stage from the separated water in liquid form therefrom at a temperature in the range 0.degree. C. to about room temperature and a pressure substantially in the range 50 to 1000 psi using asymmetric, porous, polymeric membrane material which is non-polar relative to the membrane material of the first stage as determined by .delta..sub.d of the solubility parameter of the membrane materials.