Concentration of dairy flavour compounds using pervaporation

A dilute aqueous model solution containing acids, esters and ketones (which contribute to dairy flavours) was concentrated by passing through pervaporation membranes. Polydimethylsiloxane membranes gave greater fluxes than polyoctylmethylsiloxane membranes. Fluxes increased with feed temperature and decreased with permeate pressure. Different compounds were concentrated by different amounts, meaning that the permeate composition differed from that of the feed. Esters and ketones passed through the membrane more readily than acids. Low molecular weight esters and ketones were enriched by a greater amount than larger molecules, but the influence of molecular weight was more complex for acids, and depended on the relative importance of sorption and diffusion mechanisms in the membrane.