Nanofibrous membrane for aroma compound extraction and release: a case study on coffee
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This work explores the capability of Nylon-6 nanofibrous membranes (NFM), produced with an electrospinning home-made apparatus, for the extraction of the characteristic coffee aroma compounds. Electrospinning is the simplest way to obtain nanofibers: in this technique a polymer solution is continuously pumped through a metal syringe needle; when a high voltage is applied, an electrostatic repulsion between the polymer and the metal needle causes the instantaneous ejection of the polymer, which forms nanofibers, collected as nonwoven membrane. The resulting morphology exhibits various useful characteristics for extraction of volatile compounds such as the applicability of nanofibrous membranes for aroma compound extraction and release was evaluated on a roasted Coffea arabica coffee powder from Costa Rica. In the extraction phase, solid Nylon- 6 nanofibrous membranes were briefly exposed to the headspace of the powder the coffee powder headspace as well as Nylon- 6 films. The membranes and the films were then transferred to separate vials, and their headspace was analysed by means of Proton Transfer Reaction Mass Spectrometry (PTR-MS). In a separate experiment, the headspace of the coffee powder was also by PTR-MS. Nylon nanofibrous membranes can discriminate different coffee volatile compounds because their high surface to volume ratio, high porosity and interconnectivity, meanwhile Nylon films cannot. These results demonstrate the capability of nylon nanofibrous membranes to extract and release aroma compounds under mild conditions and in sample-specific fashion. In perspective, this material could be employed in the manufacture of active packaging materials or analytical cartridges. Keywords: volatile compounds, coffee powder, PTR-MS, electrospinning, nanofibers, solid-phase extraction (SPE), Nylon.