Triggered Release of Hexanal and Benzaldehyde from their Precursors Encapsulated in Poly(lactic acid) and Ethylcellulose Carriers
Hexanal and benzaldehyde are naturally occurring antimicrobial aldehydes with (Generally recognized as safe) GRAS status. They are useful for shelf-life extension of perishable fruits and vegetables. Their high volatility and susceptibility towards oxidative degradation present considerable challenges during end-use applications. In this research, precursors of these aldehydes with enhanced stability were synthesized using a straightforward partial Schiff base reaction which converted them into imidazolidine compounds. Nuclear magnetic resonance (NMR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic analyses confirmed the heterocyclic ring-structure of the synthesized precursors. The release of aldehyde from the imidazolidine precursors can be achieved by an acid catalyzed hydrolysis reaction. To facilitate the end-use applications of these aldehyde precursors, they were encapsulated in poly(lactic acid) (PLA) or ethylcellulose (EC) polymer carrier by using electrospinning and electrospraying processes, respectively. The addition of an aqueous citric acid solution to the precursor-containing carriers triggered the release of aldehydes, the release rate and maximal quantity of which were carrier polymer and temperature dependent. Scanning electron micrographs (SEM) illustrated substantial morphological differences between pristine and precursor loaded carriers. FTIR analyses confirmed that the encapsulation of precursors inside PLA and EC carriers was mainly due to physical entrapment. This controlled release system developed in this project can potentially be used as a component of active packaging to deliver hexanal, benzaldehyde, and other aldehydes.