Kanani, DM; Nikhade, BP; Balakrishnan, P; Singh, G; Pangarkar, VG
The present work describes the possibility of using pervaporation to recover the tea aroma compounds from tea aroma condensate generated in the manufacturing of tea or instant tea, as well as directly from tea extract. Eight compounds that make a significant contribution to tea aroma, namely, trans-2-hexenal, linalool, cis-3-hexenol, 3-methylbutanal, 2-methylpropanal, benzyl alcohol, phenylacetaldehyde, and β-ionone, were studied in this work. Permeation studies for all of these compounds with poly(octyl methyl siloxane) (POMS) and poly(dimethylsiloxane) (PDMS) membranes in a batch-type vacuum pervaporation system were carried out, first, in their aqueous solutions (binary mixtures); second, in a model solution containing all of the abovementioned compounds; and last, with an actual tea extract. In this work, mainly the effect of the feed concentration on the organic flux and separation factor was studied. The permeation studies with the mixture revealed that β-ionone, trans-2-hexenal, linalool, cis-3-hexenol, and 3-methylbutanal offered very good selectivity, whereas phenylacetaldehyde, 2-methylpropanal, and benzyl alcohol gave moderate selectivity. The results indicate that pervaporation is an attractive technology for the recovery of tea aroma compounds from tea aroma condensate as it (i) yields good separation and (ii) operates under mild conditions. However, it should be noted that, because the selectivity offered by pervaporation varies considerably from compound to compound, attempts to concentrate a solution of volatiles to a high degree can result in significant alteration in the profile of the aroma. Thus, the commercial utility of this approach will need to be ascertained on a case-by-case basis.