Production of tomato flavor volatiles from a crude enzyme preparation using a hollow-fiber reactor

In recent years there has been an increase in the interest in the productio n of compounds by isolation from natural sources or through processes that can be deemed "natural". This is of particular interest in the food and bev erage industry for flavors and aromas. Hexanal, organoleptically known to p ossess "green character", is of considerable commercial interest. The objec tive of this study was to determine if the enzyme template known to be resp onsible for the synthesis of hexanal from linoleic acid (18:2) in tomato fr uits could be harnessed using a hollow-fiber reactor. A hollow-fiber reacto r system was set up and consisted of a XAMPLER ultrafiltration module coupl ed to a reservoir. The enzyme template was extracted from ripe tomato fruit s and processed through an ultrafiltration unit (NMWC of 100 kDa) to produc e a retentate enriched in soluble and membrane-associated lipoxygenase (LOX ) and hydroperoxide lyase (HPL). This extract was recirculated through the lumen of the hollow-fiber ultrafiltration unit with the addition of substra te in the form of linoleic acid, with buffer addition to the reaction flask to maintain a constant retentate volume. Product formation was measured in the permeate using solid phase microextraction (SPME) developed for this s ystem. At exogenous substrate concentrations of 16 mM and a transmembrane p ressure of 70 kPa, hexanal production rates are in the order of 5.1 mu g/mi n. Addition of Triton X-100 resulted in membrane fouling and reduced flux. The reactor system has been run for periods of up to 1 week and has been sh own to be stable over this period. (C) 2000 John Wiley & Sons, Inc.