A New Route Combining Direct-Contact Evaporation and Vapor Permeation for Obtaining High-Quality Fruit Juice Concentrates. Part I: Experimental Analysis

Abstract

An alternative rote is proposed for fruit juice processing, according to which aroma compounds are extracted by gas stripping in a bubble column and then recovered by vapor permeation, in a first step, the aroma-depleted juice being subsequently concentrated by direct-contact evaporation. To illustrate the adequacy of the proposed process, experiments were conducted with a synthetic juice, an aqueous solution of sucrose and two esters. In these tests, an aroma recovery degree of about 90% was obtained. Even though the operating pressure was slightly higher than 101 kPa, the liquid temperature did not exceed 66 °C and sucrose concentrations up to 77 wt % were achieved without any reduction in the evaporation rate. Additionally, pervaporation experiments were conducted with an aqueous solution of the esters and the flux results were compared with those related to the vapor permeation tests, revealing that the latter technique is less susceptible to concentration polarization and hence more appropriate for aroma recovery.