Concentration of flavor distillates and extracts by pervaporation

In the flavor industry concentrated flavor distillates and extracts are important products for simulating natural flavors. In the flavor concentration process the conventional evaporation method has the shortcoming of deterioration for heat sensitive flavor compounds. Pervaporation, a novel membrane separation method once used for extracting organics from wastewater, has the potential to overcome this difficulty.; In the current research hydrophobic membranes were used to extract solute (flavor organics) from solvent (water). Four polydimethyl siloxane (PDMS) membranes and one polyoctylmethyl siloxane (POMS) membrane were tested for pervaporation and compared for their separation performance. Many surrogate flavor solutions were concentrated by pervaporation using six organic compounds (cis-3-hexenol, phenethyl alcohol, benzaldehyde, trans-2-hexenal, ethyl butyrate, and methyl anthranilate) that represent three major kinds of flavor components (alcohols, aldehydes, and esters). It was possible to concentrate more flavor components in the pervaporation of real flavors. The experimental study began with the concentration of single flavor compounds; later it was extended to the pervaporation of multicomponent mixtures that resembled real flavor systems and finally to the real flavors. Both continuous and semi-batch operations were carried out. Flavor loss rate due to evaporation leakage was determined from the batch operation experiment. Operating conditions (downstream pressure, feed flow rate, feed concentration, and temperature) were optimized by the performance standards of product flux and enrichment factor. Optimum operating conditions were determined by different flavor systems and concentration requirement. A mass transfer mechanism investigation was also included in the study.; This research was the first attempt to systematically study the flavor pervaporation process. It provided significant insights regarding the possibility of concentrating dilute flavors by pervaporation. The selected operating parameters such as relatively high downstream pressure were close to those of industrial scale applications that are seldom reported in literature. The experimental results can help flavor or membrane companies select optimum operating conditions and membranes for application of the pervaporation technique. In addition, this research was the first attempt to develop a theoretical model with concentration polarization for flavor recovery by pervaporation. Traditional empirical correlations were modified or replaced by theoretical equations. The mass transfer mechanism study should be useful for membrane companies to design better pervaporation membrane processes for different applications. (Abstract shortened by UMI.)...