Recovery of Valuable Tea Aroma Components by Pervaporation

Abstract

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.

Concentration of dairy flavour compounds using pervaporation

“…Sampranpiboon et al (2000) also compared PDMS and POMS membranes for pervaporation of aqueous ethyl butanoate and ethyl hexanoate, and found that both membranes had similar ester fluxes, but that the POMS membrane had a higher separation factor because its water flux was lower. Kanani et al (2003) obtained greater separation factors with POMS membranes than with PDMS membranes for some tea aroma compounds such as linalool and cis-3-hexenol. However, PDMS membranes gave better separation factors for aldehydes and some other compounds.…”

“…POMS is more hydrophobic than PDMS because of its larger side group (Fig. 2) (Kanani et al, 2003;Trifunovic´& Tra¨ga˚rdh, 2006). Sampranpiboon et al (2000) also compared PDMS and POMS membranes for pervaporation of aqueous ethyl butanoate and ethyl hexanoate, and found that both membranes had similar ester fluxes, but that the POMS membrane had a higher separation factor because its water flux was lower.…”

“…In other cases, feed solutions were real flavour systems, such as fruit essences (Rajagopalan & Cheryan, 1995;She & Hwang, 2006a;Zhang & Matsuura, 1991), cauliflower blanching water (Souchon, Pierre, Athes-Dutour, & Marin, 2002), wine (Karlsson, Loureiro, & Tra¨ga˚rdh, 1995), tea (Kanani, Nikhade, Balakrishnan, Singh, & Pangarkar, 2003;She & Hwang, 2006a) and a marine alga (Beaucheˆne, Grua-Priol, Lamer, Demaimay, & Que´meneur, 2000). Most flavour compounds in the feed were concentrated by pervaporation, whereas feed components with low volatilities did not pass through the membrane.…”

“…However, it is difficult to predict pervaporation performance with complex feed solutions, because interactions between feed components are possible (Karlsson & Tra¨ga˚rdh, 1993;Kedem, 1989). Therefore, results with real feed mixtures did not always match those with model feeds (Kanani et al, 2003;Souchon et al, 2002).…”

Membrane-Based Extraction Techniques in Food Analysis

“…As analytes pass through the membrane, a change in volume makes the membrane more permeable, but obviously less selective, until reaching an unacceptable selectivity, and the membrane must be regenerated. Typical applications are the recovery and determination of volatile aroma compounds in fruit juice processing, [65][66][67] those that make a significant contribution to tea aroma, 68 wine, 69 or natural aroma compounds. 70 Due to different affinity for the membrane and different diffusion rate, a component at low concentration in the feed can be highly enriched in the permeate.…”